1. 04 Sep, 2015 40 commits
    • Andrea Arcangeli's avatar
      userfaultfd: mcopy_atomic|mfill_zeropage: UFFDIO_COPY|UFFDIO_ZEROPAGE preparation · c1a4de99
      Andrea Arcangeli authored
      
      
      This implements mcopy_atomic and mfill_zeropage that are the lowlevel
      VM methods that are invoked respectively by the UFFDIO_COPY and
      UFFDIO_ZEROPAGE userfaultfd commands.
      Signed-off-by: default avatarAndrea Arcangeli <aarcange@redhat.com>
      Acked-by: default avatarPavel Emelyanov <xemul@parallels.com>
      Cc: Sanidhya Kashyap <sanidhya.gatech@gmail.com>
      Cc: zhang.zhanghailiang@huawei.com
      Cc: "Kirill A. Shutemov" <kirill@shutemov.name>
      Cc: Andres Lagar-Cavilla <andreslc@google.com>
      Cc: Dave Hansen <dave.hansen@intel.com>
      Cc: Paolo Bonzini <pbonzini@redhat.com>
      Cc: Rik van Riel <riel@redhat.com>
      Cc: Mel Gorman <mgorman@suse.de>
      Cc: Andy Lutomirski <luto@amacapital.net>
      Cc: Hugh Dickins <hughd@google.com>
      Cc: Peter Feiner <pfeiner@google.com>
      Cc: "Dr. David Alan Gilbert" <dgilbert@redhat.com>
      Cc: Johannes Weiner <hannes@cmpxchg.org>
      Cc: "Huangpeng (Peter)" <peter.huangpeng@huawei.com>
      Signed-off-by: default avatarAndrew Morton <akpm@linux-foundation.org>
      Signed-off-by: default avatarLinus Torvalds <torvalds@linux-foundation.org>
      c1a4de99
    • Andrea Arcangeli's avatar
      userfaultfd: UFFDIO_COPY|UFFDIO_ZEROPAGE uAPI · 1f1c6f07
      Andrea Arcangeli authored
      
      
      This implements the uABI of UFFDIO_COPY and UFFDIO_ZEROPAGE.
      Signed-off-by: default avatarAndrea Arcangeli <aarcange@redhat.com>
      Acked-by: default avatarPavel Emelyanov <xemul@parallels.com>
      Cc: Sanidhya Kashyap <sanidhya.gatech@gmail.com>
      Cc: zhang.zhanghailiang@huawei.com
      Cc: "Kirill A. Shutemov" <kirill@shutemov.name>
      Cc: Andres Lagar-Cavilla <andreslc@google.com>
      Cc: Dave Hansen <dave.hansen@intel.com>
      Cc: Paolo Bonzini <pbonzini@redhat.com>
      Cc: Rik van Riel <riel@redhat.com>
      Cc: Mel Gorman <mgorman@suse.de>
      Cc: Andy Lutomirski <luto@amacapital.net>
      Cc: Hugh Dickins <hughd@google.com>
      Cc: Peter Feiner <pfeiner@google.com>
      Cc: "Dr. David Alan Gilbert" <dgilbert@redhat.com>
      Cc: Johannes Weiner <hannes@cmpxchg.org>
      Cc: "Huangpeng (Peter)" <peter.huangpeng@huawei.com>
      Signed-off-by: default avatarAndrew Morton <akpm@linux-foundation.org>
      Signed-off-by: default avatarLinus Torvalds <torvalds@linux-foundation.org>
      1f1c6f07
    • Andrea Arcangeli's avatar
      userfaultfd: activate syscall · 1380fca0
      Andrea Arcangeli authored
      
      
      This activates the userfaultfd syscall.
      
      [sfr@canb.auug.org.au: activate syscall fix]
      [akpm@linux-foundation.org: don't enable userfaultfd on powerpc]
      Signed-off-by: default avatarAndrea Arcangeli <aarcange@redhat.com>
      Acked-by: default avatarPavel Emelyanov <xemul@parallels.com>
      Cc: Sanidhya Kashyap <sanidhya.gatech@gmail.com>
      Cc: zhang.zhanghailiang@huawei.com
      Cc: "Kirill A. Shutemov" <kirill@shutemov.name>
      Cc: Andres Lagar-Cavilla <andreslc@google.com>
      Cc: Dave Hansen <dave.hansen@intel.com>
      Cc: Paolo Bonzini <pbonzini@redhat.com>
      Cc: Rik van Riel <riel@redhat.com>
      Cc: Mel Gorman <mgorman@suse.de>
      Cc: Andy Lutomirski <luto@amacapital.net>
      Cc: Hugh Dickins <hughd@google.com>
      Cc: Peter Feiner <pfeiner@google.com>
      Cc: "Dr. David Alan Gilbert" <dgilbert@redhat.com>
      Cc: Johannes Weiner <hannes@cmpxchg.org>
      Cc: "Huangpeng (Peter)" <peter.huangpeng@huawei.com>
      Signed-off-by: default avatarStephen Rothwell <sfr@canb.auug.org.au>
      Signed-off-by: default avatarAndrew Morton <akpm@linux-foundation.org>
      Signed-off-by: default avatarLinus Torvalds <torvalds@linux-foundation.org>
      1380fca0
    • Andrea Arcangeli's avatar
      userfaultfd: buildsystem activation · a14c151e
      Andrea Arcangeli authored
      
      
      This allows to select the userfaultfd during configuration to build it.
      Signed-off-by: default avatarAndrea Arcangeli <aarcange@redhat.com>
      Acked-by: default avatarPavel Emelyanov <xemul@parallels.com>
      Cc: Sanidhya Kashyap <sanidhya.gatech@gmail.com>
      Cc: zhang.zhanghailiang@huawei.com
      Cc: "Kirill A. Shutemov" <kirill@shutemov.name>
      Cc: Andres Lagar-Cavilla <andreslc@google.com>
      Cc: Dave Hansen <dave.hansen@intel.com>
      Cc: Paolo Bonzini <pbonzini@redhat.com>
      Cc: Rik van Riel <riel@redhat.com>
      Cc: Mel Gorman <mgorman@suse.de>
      Cc: Andy Lutomirski <luto@amacapital.net>
      Cc: Hugh Dickins <hughd@google.com>
      Cc: Peter Feiner <pfeiner@google.com>
      Cc: "Dr. David Alan Gilbert" <dgilbert@redhat.com>
      Cc: Johannes Weiner <hannes@cmpxchg.org>
      Cc: "Huangpeng (Peter)" <peter.huangpeng@huawei.com>
      Signed-off-by: default avatarAndrew Morton <akpm@linux-foundation.org>
      Signed-off-by: default avatarLinus Torvalds <torvalds@linux-foundation.org>
      a14c151e
    • Andrea Arcangeli's avatar
      userfaultfd: solve the race between UFFDIO_COPY|ZEROPAGE and read · 8d2afd96
      Andrea Arcangeli authored
      
      
      Solve in-kernel the race between UFFDIO_COPY|ZEROPAGE and
      userfaultfd_read if they are run on different threads simultaneously.
      
      Until now qemu solved the race in userland: the race was explicitly
      and intentionally left for userland to solve. However we can also
      solve it in kernel.
      
      Requiring all users to solve this race if they use two threads (one
      for the background transfer and one for the userfault reads) isn't
      very attractive from an API prospective, furthermore this allows to
      remove a whole bunch of mutex and bitmap code from qemu, making it
      faster. The cost of __get_user_pages_fast should be insignificant
      considering it scales perfectly and the pagetables are already hot in
      the CPU cache, compared to the overhead in userland to maintain those
      structures.
      
      Applying this patch is backwards compatible with respect to the
      userfaultfd userland API, however reverting this change wouldn't be
      backwards compatible anymore.
      
      Without this patch qemu in the background transfer thread, has to read
      the old state, and do UFFDIO_WAKE if old_state is missing but it
      become REQUESTED by the time it tries to set it to RECEIVED (signaling
      the other side received an userfault).
      
          vcpu                background_thr userfault_thr
          -----               -----          -----
          vcpu0 handle_mm_fault()
      
                              postcopy_place_page
                              read old_state -> MISSING
                              UFFDIO_COPY 0x7fb76a139000 (no wakeup, still pending)
      
          vcpu0 fault at 0x7fb76a139000 enters handle_userfault
          poll() is kicked
      
                                              poll() -> POLLIN
                                              read() -> 0x7fb76a139000
                                              postcopy_pmi_change_state(MISSING, REQUESTED) -> REQUESTED
      
                              tmp_state = postcopy_pmi_change_state(old_state, RECEIVED) -> REQUESTED
                              /* check that no userfault raced with UFFDIO_COPY */
                              if (old_state == MISSING && tmp_state == REQUESTED)
                                      UFFDIO_WAKE from background thread
      
      And a second case where a UFFDIO_WAKE would be needed is in the userfault thread:
      
          vcpu                background_thr userfault_thr
          -----               -----          -----
          vcpu0 handle_mm_fault()
      
                              postcopy_place_page
                              read old_state -> MISSING
                              UFFDIO_COPY 0x7fb76a139000 (no wakeup, still pending)
                              tmp_state = postcopy_pmi_change_state(old_state, RECEIVED) -> RECEIVED
      
          vcpu0 fault at 0x7fb76a139000 enters handle_userfault
          poll() is kicked
      
                                              poll() -> POLLIN
                                              read() -> 0x7fb76a139000
      
                                              if (postcopy_pmi_change_state(MISSING, REQUESTED) == RECEIVED)
                                                      UFFDIO_WAKE from userfault thread
      
      This patch removes the need of both UFFDIO_WAKE and of the associated
      per-page tristate as well.
      Signed-off-by: default avatarAndrea Arcangeli <aarcange@redhat.com>
      Acked-by: default avatarPavel Emelyanov <xemul@parallels.com>
      Cc: Sanidhya Kashyap <sanidhya.gatech@gmail.com>
      Cc: zhang.zhanghailiang@huawei.com
      Cc: "Kirill A. Shutemov" <kirill@shutemov.name>
      Cc: Andres Lagar-Cavilla <andreslc@google.com>
      Cc: Dave Hansen <dave.hansen@intel.com>
      Cc: Paolo Bonzini <pbonzini@redhat.com>
      Cc: Rik van Riel <riel@redhat.com>
      Cc: Mel Gorman <mgorman@suse.de>
      Cc: Andy Lutomirski <luto@amacapital.net>
      Cc: Hugh Dickins <hughd@google.com>
      Cc: Peter Feiner <pfeiner@google.com>
      Cc: "Dr. David Alan Gilbert" <dgilbert@redhat.com>
      Cc: Johannes Weiner <hannes@cmpxchg.org>
      Cc: "Huangpeng (Peter)" <peter.huangpeng@huawei.com>
      Signed-off-by: default avatarAndrew Morton <akpm@linux-foundation.org>
      Signed-off-by: default avatarLinus Torvalds <torvalds@linux-foundation.org>
      8d2afd96
    • Andrea Arcangeli's avatar
      userfaultfd: allocate the userfaultfd_ctx cacheline aligned · 3004ec9c
      Andrea Arcangeli authored
      
      
      Use proper slab to guarantee alignment.
      Signed-off-by: default avatarAndrea Arcangeli <aarcange@redhat.com>
      Acked-by: default avatarPavel Emelyanov <xemul@parallels.com>
      Cc: Sanidhya Kashyap <sanidhya.gatech@gmail.com>
      Cc: zhang.zhanghailiang@huawei.com
      Cc: "Kirill A. Shutemov" <kirill@shutemov.name>
      Cc: Andres Lagar-Cavilla <andreslc@google.com>
      Cc: Dave Hansen <dave.hansen@intel.com>
      Cc: Paolo Bonzini <pbonzini@redhat.com>
      Cc: Rik van Riel <riel@redhat.com>
      Cc: Mel Gorman <mgorman@suse.de>
      Cc: Andy Lutomirski <luto@amacapital.net>
      Cc: Hugh Dickins <hughd@google.com>
      Cc: Peter Feiner <pfeiner@google.com>
      Cc: "Dr. David Alan Gilbert" <dgilbert@redhat.com>
      Cc: Johannes Weiner <hannes@cmpxchg.org>
      Cc: "Huangpeng (Peter)" <peter.huangpeng@huawei.com>
      Signed-off-by: default avatarAndrew Morton <akpm@linux-foundation.org>
      Signed-off-by: default avatarLinus Torvalds <torvalds@linux-foundation.org>
      3004ec9c
    • Andrea Arcangeli's avatar
      userfaultfd: optimize read() and poll() to be O(1) · 15b726ef
      Andrea Arcangeli authored
      
      
      This makes read O(1) and poll that was already O(1) becomes lockless.
      Signed-off-by: default avatarAndrea Arcangeli <aarcange@redhat.com>
      Acked-by: default avatarPavel Emelyanov <xemul@parallels.com>
      Cc: Sanidhya Kashyap <sanidhya.gatech@gmail.com>
      Cc: zhang.zhanghailiang@huawei.com
      Cc: "Kirill A. Shutemov" <kirill@shutemov.name>
      Cc: Andres Lagar-Cavilla <andreslc@google.com>
      Cc: Dave Hansen <dave.hansen@intel.com>
      Cc: Paolo Bonzini <pbonzini@redhat.com>
      Cc: Rik van Riel <riel@redhat.com>
      Cc: Mel Gorman <mgorman@suse.de>
      Cc: Andy Lutomirski <luto@amacapital.net>
      Cc: Hugh Dickins <hughd@google.com>
      Cc: Peter Feiner <pfeiner@google.com>
      Cc: "Dr. David Alan Gilbert" <dgilbert@redhat.com>
      Cc: Johannes Weiner <hannes@cmpxchg.org>
      Cc: "Huangpeng (Peter)" <peter.huangpeng@huawei.com>
      Signed-off-by: default avatarAndrew Morton <akpm@linux-foundation.org>
      Signed-off-by: default avatarLinus Torvalds <torvalds@linux-foundation.org>
      15b726ef
    • Andrea Arcangeli's avatar
      userfaultfd: wake pending userfaults · ba85c702
      Andrea Arcangeli authored
      
      
      This is an optimization but it's a userland visible one and it affects
      the API.
      
      The downside of this optimization is that if you call poll() and you
      get POLLIN, read(ufd) may still return -EAGAIN. The blocked userfault
      may be waken by a different thread, before read(ufd) comes
      around. This in short means that poll() isn't really usable if the
      userfaultfd is opened in blocking mode.
      
      userfaults won't wait in "pending" state to be read anymore and any
      UFFDIO_WAKE or similar operations that has the objective of waking
      userfaults after their resolution, will wake all blocked userfaults
      for the resolved range, including those that haven't been read() by
      userland yet.
      
      The behavior of poll() becomes not standard, but this obviates the
      need of "spurious" UFFDIO_WAKE and it lets the userland threads to
      restart immediately without requiring an UFFDIO_WAKE. This is even
      more significant in case of repeated faults on the same address from
      multiple threads.
      
      This optimization is justified by the measurement that the number of
      spurious UFFDIO_WAKE accounts for 5% and 10% of the total
      userfaults for heavy workloads, so it's worth optimizing those away.
      Signed-off-by: default avatarAndrea Arcangeli <aarcange@redhat.com>
      Acked-by: default avatarPavel Emelyanov <xemul@parallels.com>
      Cc: Sanidhya Kashyap <sanidhya.gatech@gmail.com>
      Cc: zhang.zhanghailiang@huawei.com
      Cc: "Kirill A. Shutemov" <kirill@shutemov.name>
      Cc: Andres Lagar-Cavilla <andreslc@google.com>
      Cc: Dave Hansen <dave.hansen@intel.com>
      Cc: Paolo Bonzini <pbonzini@redhat.com>
      Cc: Rik van Riel <riel@redhat.com>
      Cc: Mel Gorman <mgorman@suse.de>
      Cc: Andy Lutomirski <luto@amacapital.net>
      Cc: Hugh Dickins <hughd@google.com>
      Cc: Peter Feiner <pfeiner@google.com>
      Cc: "Dr. David Alan Gilbert" <dgilbert@redhat.com>
      Cc: Johannes Weiner <hannes@cmpxchg.org>
      Cc: "Huangpeng (Peter)" <peter.huangpeng@huawei.com>
      Signed-off-by: default avatarAndrew Morton <akpm@linux-foundation.org>
      Signed-off-by: default avatarLinus Torvalds <torvalds@linux-foundation.org>
      ba85c702
    • Andrea Arcangeli's avatar
      userfaultfd: change the read API to return a uffd_msg · a9b85f94
      Andrea Arcangeli authored
      
      
      I had requests to return the full address (not the page aligned one) to
      userland.
      
      It's not entirely clear how the page offset could be relevant because
      userfaults aren't like SIGBUS that can sigjump to a different place and it
      actually skip resolving the fault depending on a page offset.  There's
      currently no real way to skip the fault especially because after a
      UFFDIO_COPY|ZEROPAGE, the fault is optimized to be retried within the
      kernel without having to return to userland first (not even self modifying
      code replacing the .text that touched the faulting address would prevent
      the fault to be repeated).  Userland cannot skip repeating the fault even
      more so if the fault was triggered by a KVM secondary page fault or any
      get_user_pages or any copy-user inside some syscall which will return to
      kernel code.  The second time FAULT_FLAG_RETRY_NOWAIT won't be set leading
      to a SIGBUS being raised because the userfault can't wait if it cannot
      release the mmap_map first (and FAULT_FLAG_RETRY_NOWAIT is required for
      that).
      
      Still returning userland a proper structure during the read() on the uffd,
      can allow to use the current UFFD_API for the future non-cooperative
      extensions too and it looks cleaner as well.  Once we get additional
      fields there's no point to return the fault address page aligned anymore
      to reuse the bits below PAGE_SHIFT.
      
      The only downside is that the read() syscall will read 32bytes instead of
      8bytes but that's not going to be measurable overhead.
      
      The total number of new events that can be extended or of new future bits
      for already shipped events, is limited to 64 by the features field of the
      uffdio_api structure.  If more will be needed a bump of UFFD_API will be
      required.
      
      [akpm@linux-foundation.org: use __packed]
      Signed-off-by: default avatarAndrea Arcangeli <aarcange@redhat.com>
      Acked-by: default avatarPavel Emelyanov <xemul@parallels.com>
      Cc: Sanidhya Kashyap <sanidhya.gatech@gmail.com>
      Cc: zhang.zhanghailiang@huawei.com
      Cc: "Kirill A. Shutemov" <kirill@shutemov.name>
      Cc: Andres Lagar-Cavilla <andreslc@google.com>
      Cc: Dave Hansen <dave.hansen@intel.com>
      Cc: Paolo Bonzini <pbonzini@redhat.com>
      Cc: Rik van Riel <riel@redhat.com>
      Cc: Mel Gorman <mgorman@suse.de>
      Cc: Andy Lutomirski <luto@amacapital.net>
      Cc: Hugh Dickins <hughd@google.com>
      Cc: Peter Feiner <pfeiner@google.com>
      Cc: "Dr. David Alan Gilbert" <dgilbert@redhat.com>
      Cc: Johannes Weiner <hannes@cmpxchg.org>
      Cc: "Huangpeng (Peter)" <peter.huangpeng@huawei.com>
      Signed-off-by: default avatarAndrew Morton <akpm@linux-foundation.org>
      Signed-off-by: default avatarLinus Torvalds <torvalds@linux-foundation.org>
      a9b85f94
    • Pavel Emelyanov's avatar
      userfaultfd: Rename uffd_api.bits into .features · 3f602d27
      Pavel Emelyanov authored
      
      
      This is (seems to be) the minimal thing that is required to unblock
      standard uffd usage from the non-cooperative one.  Now more bits can be
      added to the features field indicating e.g.  UFFD_FEATURE_FORK and others
      needed for the latter use-case.
      Signed-off-by: default avatarPavel Emelyanov <xemul@parallels.com>
      Signed-off-by: default avatarAndrea Arcangeli <aarcange@redhat.com>
      Cc: Sanidhya Kashyap <sanidhya.gatech@gmail.com>
      Cc: zhang.zhanghailiang@huawei.com
      Cc: "Kirill A. Shutemov" <kirill@shutemov.name>
      Cc: Andres Lagar-Cavilla <andreslc@google.com>
      Cc: Dave Hansen <dave.hansen@intel.com>
      Cc: Paolo Bonzini <pbonzini@redhat.com>
      Cc: Rik van Riel <riel@redhat.com>
      Cc: Mel Gorman <mgorman@suse.de>
      Cc: Andy Lutomirski <luto@amacapital.net>
      Cc: Hugh Dickins <hughd@google.com>
      Cc: Peter Feiner <pfeiner@google.com>
      Cc: "Dr. David Alan Gilbert" <dgilbert@redhat.com>
      Cc: Johannes Weiner <hannes@cmpxchg.org>
      Cc: "Huangpeng (Peter)" <peter.huangpeng@huawei.com>
      Signed-off-by: default avatarAndrew Morton <akpm@linux-foundation.org>
      Signed-off-by: default avatarLinus Torvalds <torvalds@linux-foundation.org>
      3f602d27
    • Andrea Arcangeli's avatar
      userfaultfd: add new syscall to provide memory externalization · 86039bd3
      Andrea Arcangeli authored
      
      
      Once an userfaultfd has been created and certain region of the process
      virtual address space have been registered into it, the thread responsible
      for doing the memory externalization can manage the page faults in
      userland by talking to the kernel using the userfaultfd protocol.
      
      poll() can be used to know when there are new pending userfaults to be
      read (POLLIN).
      Signed-off-by: default avatarAndrea Arcangeli <aarcange@redhat.com>
      Acked-by: default avatarPavel Emelyanov <xemul@parallels.com>
      Cc: Sanidhya Kashyap <sanidhya.gatech@gmail.com>
      Cc: zhang.zhanghailiang@huawei.com
      Cc: "Kirill A. Shutemov" <kirill@shutemov.name>
      Cc: Andres Lagar-Cavilla <andreslc@google.com>
      Cc: Dave Hansen <dave.hansen@intel.com>
      Cc: Paolo Bonzini <pbonzini@redhat.com>
      Cc: Rik van Riel <riel@redhat.com>
      Cc: Mel Gorman <mgorman@suse.de>
      Cc: Andy Lutomirski <luto@amacapital.net>
      Cc: Hugh Dickins <hughd@google.com>
      Cc: Peter Feiner <pfeiner@google.com>
      Cc: "Dr. David Alan Gilbert" <dgilbert@redhat.com>
      Cc: Johannes Weiner <hannes@cmpxchg.org>
      Cc: "Huangpeng (Peter)" <peter.huangpeng@huawei.com>
      Cc: Dan Carpenter <dan.carpenter@oracle.com>
      Signed-off-by: default avatarAndrew Morton <akpm@linux-foundation.org>
      Signed-off-by: default avatarLinus Torvalds <torvalds@linux-foundation.org>
      86039bd3
    • Andrea Arcangeli's avatar
      userfaultfd: prevent khugepaged to merge if userfaultfd is armed · c1294d05
      Andrea Arcangeli authored
      
      
      If userfaultfd is armed on a certain vma we can't "fill" the holes with
      zeroes or we'll break the userland on demand paging.  The holes if the
      userfault is armed, are really missing information (not zeroes) that the
      userland has to load from network or elsewhere.
      
      The same issue happens for wrprotected ptes that we can't just convert
      into a single writable pmd_trans_huge.
      
      We could however in theory still merge across zeropages if only
      VM_UFFD_MISSING is set (so if VM_UFFD_WP is not set)...  that could be
      slightly improved but it'd be much more complex code for a tiny corner
      case.
      Signed-off-by: default avatarAndrea Arcangeli <aarcange@redhat.com>
      Acked-by: default avatarPavel Emelyanov <xemul@parallels.com>
      Cc: Sanidhya Kashyap <sanidhya.gatech@gmail.com>
      Cc: zhang.zhanghailiang@huawei.com
      Cc: "Kirill A. Shutemov" <kirill@shutemov.name>
      Cc: Andres Lagar-Cavilla <andreslc@google.com>
      Cc: Dave Hansen <dave.hansen@intel.com>
      Cc: Paolo Bonzini <pbonzini@redhat.com>
      Cc: Rik van Riel <riel@redhat.com>
      Cc: Mel Gorman <mgorman@suse.de>
      Cc: Andy Lutomirski <luto@amacapital.net>
      Cc: Hugh Dickins <hughd@google.com>
      Cc: Peter Feiner <pfeiner@google.com>
      Cc: "Dr. David Alan Gilbert" <dgilbert@redhat.com>
      Cc: Johannes Weiner <hannes@cmpxchg.org>
      Cc: "Huangpeng (Peter)" <peter.huangpeng@huawei.com>
      Signed-off-by: default avatarAndrew Morton <akpm@linux-foundation.org>
      Signed-off-by: default avatarLinus Torvalds <torvalds@linux-foundation.org>
      c1294d05
    • Andrea Arcangeli's avatar
      userfaultfd: teach vma_merge to merge across vma->vm_userfaultfd_ctx · 19a809af
      Andrea Arcangeli authored
      
      
      vma->vm_userfaultfd_ctx is yet another vma parameter that vma_merge
      must be aware about so that we can merge vmas back like they were
      originally before arming the userfaultfd on some memory range.
      Signed-off-by: default avatarAndrea Arcangeli <aarcange@redhat.com>
      Acked-by: default avatarPavel Emelyanov <xemul@parallels.com>
      Cc: Sanidhya Kashyap <sanidhya.gatech@gmail.com>
      Cc: zhang.zhanghailiang@huawei.com
      Cc: "Kirill A. Shutemov" <kirill@shutemov.name>
      Cc: Andres Lagar-Cavilla <andreslc@google.com>
      Cc: Dave Hansen <dave.hansen@intel.com>
      Cc: Paolo Bonzini <pbonzini@redhat.com>
      Cc: Rik van Riel <riel@redhat.com>
      Cc: Mel Gorman <mgorman@suse.de>
      Cc: Andy Lutomirski <luto@amacapital.net>
      Cc: Hugh Dickins <hughd@google.com>
      Cc: Peter Feiner <pfeiner@google.com>
      Cc: "Dr. David Alan Gilbert" <dgilbert@redhat.com>
      Cc: Johannes Weiner <hannes@cmpxchg.org>
      Cc: "Huangpeng (Peter)" <peter.huangpeng@huawei.com>
      Signed-off-by: default avatarAndrew Morton <akpm@linux-foundation.org>
      Signed-off-by: default avatarLinus Torvalds <torvalds@linux-foundation.org>
      19a809af
    • Andrea Arcangeli's avatar
      userfaultfd: call handle_userfault() for userfaultfd_missing() faults · 6b251fc9
      Andrea Arcangeli authored
      
      
      This is where the page faults must be modified to call
      handle_userfault() if userfaultfd_missing() is true (so if the
      vma->vm_flags had VM_UFFD_MISSING set).
      
      handle_userfault() then takes care of blocking the page fault and
      delivering it to userland.
      
      The fault flags must also be passed as parameter so the "read|write"
      kind of fault can be passed to userland.
      Signed-off-by: default avatarAndrea Arcangeli <aarcange@redhat.com>
      Acked-by: default avatarPavel Emelyanov <xemul@parallels.com>
      Cc: Sanidhya Kashyap <sanidhya.gatech@gmail.com>
      Cc: zhang.zhanghailiang@huawei.com
      Cc: "Kirill A. Shutemov" <kirill@shutemov.name>
      Cc: Andres Lagar-Cavilla <andreslc@google.com>
      Cc: Dave Hansen <dave.hansen@intel.com>
      Cc: Paolo Bonzini <pbonzini@redhat.com>
      Cc: Rik van Riel <riel@redhat.com>
      Cc: Mel Gorman <mgorman@suse.de>
      Cc: Andy Lutomirski <luto@amacapital.net>
      Cc: Hugh Dickins <hughd@google.com>
      Cc: Peter Feiner <pfeiner@google.com>
      Cc: "Dr. David Alan Gilbert" <dgilbert@redhat.com>
      Cc: Johannes Weiner <hannes@cmpxchg.org>
      Cc: "Huangpeng (Peter)" <peter.huangpeng@huawei.com>
      Signed-off-by: default avatarAndrew Morton <akpm@linux-foundation.org>
      Signed-off-by: default avatarLinus Torvalds <torvalds@linux-foundation.org>
      6b251fc9
    • Andrea Arcangeli's avatar
      userfaultfd: add VM_UFFD_MISSING and VM_UFFD_WP · 16ba6f81
      Andrea Arcangeli authored
      
      
      These two flags gets set in vma->vm_flags to tell the VM common code
      if the userfaultfd is armed and in which mode (only tracking missing
      faults, only tracking wrprotect faults or both). If neither flags is
      set it means the userfaultfd is not armed on the vma.
      Signed-off-by: default avatarAndrea Arcangeli <aarcange@redhat.com>
      Acked-by: default avatarPavel Emelyanov <xemul@parallels.com>
      Cc: Sanidhya Kashyap <sanidhya.gatech@gmail.com>
      Cc: zhang.zhanghailiang@huawei.com
      Cc: "Kirill A. Shutemov" <kirill@shutemov.name>
      Cc: Andres Lagar-Cavilla <andreslc@google.com>
      Cc: Dave Hansen <dave.hansen@intel.com>
      Cc: Paolo Bonzini <pbonzini@redhat.com>
      Cc: Rik van Riel <riel@redhat.com>
      Cc: Mel Gorman <mgorman@suse.de>
      Cc: Andy Lutomirski <luto@amacapital.net>
      Cc: Hugh Dickins <hughd@google.com>
      Cc: Peter Feiner <pfeiner@google.com>
      Cc: "Dr. David Alan Gilbert" <dgilbert@redhat.com>
      Cc: Johannes Weiner <hannes@cmpxchg.org>
      Cc: "Huangpeng (Peter)" <peter.huangpeng@huawei.com>
      Signed-off-by: default avatarAndrew Morton <akpm@linux-foundation.org>
      Signed-off-by: default avatarLinus Torvalds <torvalds@linux-foundation.org>
      16ba6f81
    • Andrea Arcangeli's avatar
      userfaultfd: add vm_userfaultfd_ctx to the vm_area_struct · 745f234b
      Andrea Arcangeli authored
      
      
      This adds the vm_userfaultfd_ctx to the vm_area_struct.
      Signed-off-by: default avatarAndrea Arcangeli <aarcange@redhat.com>
      Acked-by: default avatarPavel Emelyanov <xemul@parallels.com>
      Cc: Sanidhya Kashyap <sanidhya.gatech@gmail.com>
      Cc: zhang.zhanghailiang@huawei.com
      Cc: "Kirill A. Shutemov" <kirill@shutemov.name>
      Cc: Andres Lagar-Cavilla <andreslc@google.com>
      Cc: Dave Hansen <dave.hansen@intel.com>
      Cc: Paolo Bonzini <pbonzini@redhat.com>
      Cc: Rik van Riel <riel@redhat.com>
      Cc: Mel Gorman <mgorman@suse.de>
      Cc: Andy Lutomirski <luto@amacapital.net>
      Cc: Hugh Dickins <hughd@google.com>
      Cc: Peter Feiner <pfeiner@google.com>
      Cc: "Dr. David Alan Gilbert" <dgilbert@redhat.com>
      Cc: Johannes Weiner <hannes@cmpxchg.org>
      Cc: "Huangpeng (Peter)" <peter.huangpeng@huawei.com>
      Signed-off-by: default avatarAndrew Morton <akpm@linux-foundation.org>
      Signed-off-by: default avatarLinus Torvalds <torvalds@linux-foundation.org>
      745f234b
    • Andrea Arcangeli's avatar
      userfaultfd: linux/userfaultfd_k.h · 932b18e0
      Andrea Arcangeli authored
      
      
      Kernel header defining the methods needed by the VM common code to
      interact with the userfaultfd.
      Signed-off-by: default avatarAndrea Arcangeli <aarcange@redhat.com>
      Acked-by: default avatarPavel Emelyanov <xemul@parallels.com>
      Cc: Sanidhya Kashyap <sanidhya.gatech@gmail.com>
      Cc: zhang.zhanghailiang@huawei.com
      Cc: "Kirill A. Shutemov" <kirill@shutemov.name>
      Cc: Andres Lagar-Cavilla <andreslc@google.com>
      Cc: Dave Hansen <dave.hansen@intel.com>
      Cc: Paolo Bonzini <pbonzini@redhat.com>
      Cc: Rik van Riel <riel@redhat.com>
      Cc: Mel Gorman <mgorman@suse.de>
      Cc: Andy Lutomirski <luto@amacapital.net>
      Cc: Hugh Dickins <hughd@google.com>
      Cc: Peter Feiner <pfeiner@google.com>
      Cc: "Dr. David Alan Gilbert" <dgilbert@redhat.com>
      Cc: Johannes Weiner <hannes@cmpxchg.org>
      Cc: "Huangpeng (Peter)" <peter.huangpeng@huawei.com>
      Signed-off-by: default avatarAndrew Morton <akpm@linux-foundation.org>
      Signed-off-by: default avatarLinus Torvalds <torvalds@linux-foundation.org>
      932b18e0
    • Andrea Arcangeli's avatar
      userfaultfd: uAPI · 1038628d
      Andrea Arcangeli authored
      
      
      Defines the uAPI of the userfaultfd, notably the ioctl numbers and protocol.
      Signed-off-by: default avatarAndrea Arcangeli <aarcange@redhat.com>
      Acked-by: default avatarPavel Emelyanov <xemul@parallels.com>
      Cc: Sanidhya Kashyap <sanidhya.gatech@gmail.com>
      Cc: zhang.zhanghailiang@huawei.com
      Cc: "Kirill A. Shutemov" <kirill@shutemov.name>
      Cc: Andres Lagar-Cavilla <andreslc@google.com>
      Cc: Dave Hansen <dave.hansen@intel.com>
      Cc: Paolo Bonzini <pbonzini@redhat.com>
      Cc: Rik van Riel <riel@redhat.com>
      Cc: Mel Gorman <mgorman@suse.de>
      Cc: Andy Lutomirski <luto@amacapital.net>
      Cc: Hugh Dickins <hughd@google.com>
      Cc: Peter Feiner <pfeiner@google.com>
      Cc: "Dr. David Alan Gilbert" <dgilbert@redhat.com>
      Cc: Johannes Weiner <hannes@cmpxchg.org>
      Cc: "Huangpeng (Peter)" <peter.huangpeng@huawei.com>
      Signed-off-by: default avatarAndrew Morton <akpm@linux-foundation.org>
      Signed-off-by: default avatarLinus Torvalds <torvalds@linux-foundation.org>
      1038628d
    • Andrea Arcangeli's avatar
      userfaultfd: waitqueue: add nr wake parameter to __wake_up_locked_key · 51360155
      Andrea Arcangeli authored
      
      
      userfaultfd needs to wake all waitqueues (pass 0 as nr parameter), instead
      of the current hardcoded 1 (that would wake just the first waitqueue in
      the head list).
      Signed-off-by: default avatarAndrea Arcangeli <aarcange@redhat.com>
      Acked-by: default avatarPavel Emelyanov <xemul@parallels.com>
      Cc: Sanidhya Kashyap <sanidhya.gatech@gmail.com>
      Cc: zhang.zhanghailiang@huawei.com
      Cc: "Kirill A. Shutemov" <kirill@shutemov.name>
      Cc: Andres Lagar-Cavilla <andreslc@google.com>
      Cc: Dave Hansen <dave.hansen@intel.com>
      Cc: Paolo Bonzini <pbonzini@redhat.com>
      Cc: Rik van Riel <riel@redhat.com>
      Cc: Mel Gorman <mgorman@suse.de>
      Cc: Andy Lutomirski <luto@amacapital.net>
      Cc: Hugh Dickins <hughd@google.com>
      Cc: Peter Feiner <pfeiner@google.com>
      Cc: "Dr. David Alan Gilbert" <dgilbert@redhat.com>
      Cc: Johannes Weiner <hannes@cmpxchg.org>
      Cc: "Huangpeng (Peter)" <peter.huangpeng@huawei.com>
      Signed-off-by: default avatarAndrew Morton <akpm@linux-foundation.org>
      Signed-off-by: default avatarLinus Torvalds <torvalds@linux-foundation.org>
      51360155
    • Andrea Arcangeli's avatar
      userfaultfd: linux/Documentation/vm/userfaultfd.txt · 25edd8bf
      Andrea Arcangeli authored
      This is the latest userfaultfd patchset.  The postcopy live migration
      feature on the qemu side is mostly ready to be merged and it entirely
      depends on the userfaultfd syscall to be merged as well.  So it'd be great
      if this patchset could be reviewed for merging in -mm.
      
      Userfaults allow to implement on demand paging from userland and more
      generally they allow userland to more efficiently take control of the
      behavior of page faults than what was available before (PROT_NONE +
      SIGSEGV trap).
      
      The use cases are:
      
      1) KVM postcopy live migration (one form of cloud memory
         externalization).
      
         KVM postcopy live migration is the primary driver of this work:
      
          http://blog.zhaw.ch/icclab/setting-up-post-copy-live-migration-in-openstack/
          http://lists.gnu.org/archive/html/qemu-devel/2015-02/msg04873.html
      
      2) postcopy live migration of binaries inside linux containers:
      
          http://thread.gmane.org/gmane.linux.kernel.mm/132662
      
      
      
      3) KVM postcopy live snapshotting (allowing to limit/throttle the
         memory usage, unlike fork would, plus the avoidance of fork
         overhead in the first place).
      
         While the wrprotect tracking is not implemented yet, the syscall API is
         already contemplating the wrprotect fault tracking and it's generic enough
         to allow its later implementation in a backwards compatible fashion.
      
      4) KVM userfaults on shared memory. The UFFDIO_COPY lowlevel method
         should be extended to work also on tmpfs and then the
         uffdio_register.ioctls will notify userland that UFFDIO_COPY is
         available even when the registered virtual memory range is tmpfs
         backed.
      
      5) alternate mechanism to notify web browsers or apps on embedded
         devices that volatile pages have been reclaimed. This basically
         avoids the need to run a syscall before the app can access with the
         CPU the virtual regions marked volatile. This depends on point 4)
         to be fulfilled first, as volatile pages happily apply to tmpfs.
      
      Even though there wasn't a real use case requesting it yet, it also
      allows to implement distributed shared memory in a way that readonly
      shared mappings can exist simultaneously in different hosts and they
      can be become exclusive at the first wrprotect fault.
      
      This patch (of 22):
      
      Add documentation.
      Signed-off-by: default avatarAndrea Arcangeli <aarcange@redhat.com>
      Acked-by: default avatarPavel Emelyanov <xemul@parallels.com>
      Cc: Sanidhya Kashyap <sanidhya.gatech@gmail.com>
      Cc: zhang.zhanghailiang@huawei.com
      Cc: "Kirill A. Shutemov" <kirill@shutemov.name>
      Cc: Andres Lagar-Cavilla <andreslc@google.com>
      Cc: Dave Hansen <dave.hansen@intel.com>
      Cc: Paolo Bonzini <pbonzini@redhat.com>
      Cc: Rik van Riel <riel@redhat.com>
      Cc: Mel Gorman <mgorman@suse.de>
      Cc: Andy Lutomirski <luto@amacapital.net>
      Cc: Hugh Dickins <hughd@google.com>
      Cc: Peter Feiner <pfeiner@google.com>
      Cc: "Dr. David Alan Gilbert" <dgilbert@redhat.com>
      Cc: Johannes Weiner <hannes@cmpxchg.org>
      Cc: "Huangpeng (Peter)" <peter.huangpeng@huawei.com>
      Signed-off-by: default avatarAndrew Morton <akpm@linux-foundation.org>
      Signed-off-by: default avatarLinus Torvalds <torvalds@linux-foundation.org>
      25edd8bf
    • Daniel Borkmann's avatar
      mm/slab.h: fix argument order in cache_from_obj's error message · 2d16e0fd
      Daniel Borkmann authored
      
      
      While debugging a networking issue, I hit a condition that triggered an
      object to be freed into the wrong kmem cache, and thus triggered the
      warning in cache_from_obj().
      
      The arguments in the error message are in wrong order: the location
      of the object's kmem cache is in cachep, not s.
      Signed-off-by: default avatarDaniel Borkmann <daniel@iogearbox.net>
      Cc: Christoph Lameter <cl@linux.com>
      Cc: Pekka Enberg <penberg@kernel.org>
      Cc: David Rientjes <rientjes@google.com>
      Cc: Joonsoo Kim <iamjoonsoo.kim@lge.com>
      Signed-off-by: default avatarAndrew Morton <akpm@linux-foundation.org>
      Signed-off-by: default avatarLinus Torvalds <torvalds@linux-foundation.org>
      2d16e0fd
    • Joonsoo Kim's avatar
      mm/slub: don't wait for high-order page allocation · 45eb00cd
      Joonsoo Kim authored
      Description is almost copied from commit fb05e7a8
      
       ("net: don't wait
      for order-3 page allocation").
      
      I saw excessive direct memory reclaim/compaction triggered by slub.  This
      causes performance issues and add latency.  Slub uses high-order
      allocation to reduce internal fragmentation and management overhead.  But,
      direct memory reclaim/compaction has high overhead and the benefit of
      high-order allocation can't compensate the overhead of both work.
      
      This patch makes auxiliary high-order allocation atomic.  If there is no
      memory pressure and memory isn't fragmented, the alloction will still
      success, so we don't sacrifice high-order allocation's benefit here.  If
      the atomic allocation fails, direct memory reclaim/compaction will not be
      triggered, allocation fallback to low-order immediately, hence the direct
      memory reclaim/compaction overhead is avoided.  In the allocation failure
      case, kswapd is waken up and trying to make high-order freepages, so
      allocation could success next time.
      
      Following is the test to measure effect of this patch.
      
      System: QEMU, CPU 8, 512 MB
      Mem: 25% memory is allocated at random position to make fragmentation.
       Memory-hogger occupies 150 MB memory.
      Workload: hackbench -g 20 -l 1000
      
      Average result by 10 runs (Base va Patched)
      
      elapsed_time(s): 4.3468 vs 2.9838
      compact_stall: 461.7 vs 73.6
      pgmigrate_success: 28315.9 vs 7256.1
      Signed-off-by: default avatarJoonsoo Kim <iamjoonsoo.kim@lge.com>
      Cc: Christoph Lameter <cl@linux.com>
      Cc: Pekka Enberg <penberg@kernel.org>
      Acked-by: default avatarDavid Rientjes <rientjes@google.com>
      Cc: Shaohua Li <shli@fb.com>
      Cc: Vlastimil Babka <vbabka@suse.cz>
      Cc: Michal Hocko <mhocko@suse.cz>
      Cc: Eric Dumazet <edumazet@google.com>
      Signed-off-by: default avatarAndrew Morton <akpm@linux-foundation.org>
      Signed-off-by: default avatarLinus Torvalds <torvalds@linux-foundation.org>
      45eb00cd
    • Konstantin Khlebnikov's avatar
      mm/slub: fix slab double-free in case of duplicate sysfs filename · 80da026a
      Konstantin Khlebnikov authored
      
      
      sysfs_slab_add() shouldn't call kobject_put at error path: this puts last
      reference of kmem-cache kobject and frees it.  Kmem cache will be freed
      second time at error path in kmem_cache_create().
      
      For example this happens when slub debug was enabled in runtime and
      somebody creates new kmem cache:
      
      # echo 1 | tee /sys/kernel/slab/*/sanity_checks
      # modprobe configfs
      
      "configfs_dir_cache" cannot be merged because existing slab have debug and
      cannot create new slab because unique name ":t-0000096" already taken.
      Signed-off-by: default avatarKonstantin Khlebnikov <khlebnikov@yandex-team.ru>
      Acked-by: default avatarChristoph Lameter <cl@linux.com>
      Cc: Pekka Enberg <penberg@kernel.org>
      Acked-by: default avatarDavid Rientjes <rientjes@google.com>
      Cc: Joonsoo Kim <iamjoonsoo.kim@lge.com>
      Signed-off-by: default avatarAndrew Morton <akpm@linux-foundation.org>
      Signed-off-by: default avatarLinus Torvalds <torvalds@linux-foundation.org>
      80da026a
    • Thomas Gleixner's avatar
      mm/slub: move slab initialization into irq enabled region · 588f8ba9
      Thomas Gleixner authored
      
      
      Initializing a new slab can introduce rather large latencies because most
      of the initialization runs always with interrupts disabled.
      
      There is no point in doing so.  The newly allocated slab is not visible
      yet, so there is no reason to protect it against concurrent alloc/free.
      
      Move the expensive parts of the initialization into allocate_slab(), so
      for all allocations with GFP_WAIT set, interrupts are enabled.
      Signed-off-by: default avatarThomas Gleixner <tglx@linutronix.de>
      Acked-by: default avatarChristoph Lameter <cl@linux.com>
      Cc: Pekka Enberg <penberg@kernel.org>
      Acked-by: default avatarDavid Rientjes <rientjes@google.com>
      Cc: Joonsoo Kim <iamjoonsoo.kim@lge.com>
      Cc: Sebastian Andrzej Siewior <bigeasy@linutronix.de>
      Cc: Steven Rostedt <rostedt@goodmis.org>
      Cc: Peter Zijlstra <peterz@infradead.org>
      Signed-off-by: default avatarAndrew Morton <akpm@linux-foundation.org>
      Signed-off-by: default avatarLinus Torvalds <torvalds@linux-foundation.org>
      588f8ba9
    • Jesper Dangaard Brouer's avatar
      slub: add support for kmem_cache_debug in bulk calls · 3eed034d
      Jesper Dangaard Brouer authored
      
      
      Per request of Joonsoo Kim adding kmem debug support.
      
      I've tested that when debugging is disabled, then there is almost no
      performance impact as this code basically gets removed by the compiler.
      
      Need some guidance in enabling and testing this.
      
      bulk- PREVIOUS                  - THIS-PATCH
        1 -  43 cycles(tsc) 10.811 ns -  44 cycles(tsc) 11.236 ns  improved  -2.3%
        2 -  27 cycles(tsc)  6.867 ns -  28 cycles(tsc)  7.019 ns  improved  -3.7%
        3 -  21 cycles(tsc)  5.496 ns -  22 cycles(tsc)  5.526 ns  improved  -4.8%
        4 -  24 cycles(tsc)  6.038 ns -  19 cycles(tsc)  4.786 ns  improved  20.8%
        8 -  17 cycles(tsc)  4.280 ns -  18 cycles(tsc)  4.572 ns  improved  -5.9%
       16 -  17 cycles(tsc)  4.483 ns -  18 cycles(tsc)  4.658 ns  improved  -5.9%
       30 -  18 cycles(tsc)  4.531 ns -  18 cycles(tsc)  4.568 ns  improved   0.0%
       32 -  58 cycles(tsc) 14.586 ns -  65 cycles(tsc) 16.454 ns  improved -12.1%
       34 -  53 cycles(tsc) 13.391 ns -  63 cycles(tsc) 15.932 ns  improved -18.9%
       48 -  65 cycles(tsc) 16.268 ns -  50 cycles(tsc) 12.506 ns  improved  23.1%
       64 -  53 cycles(tsc) 13.440 ns -  63 cycles(tsc) 15.929 ns  improved -18.9%
      128 -  79 cycles(tsc) 19.899 ns -  86 cycles(tsc) 21.583 ns  improved  -8.9%
      158 -  90 cycles(tsc) 22.732 ns -  90 cycles(tsc) 22.552 ns  improved   0.0%
      250 -  95 cycles(tsc) 23.916 ns -  98 cycles(tsc) 24.589 ns  improved  -3.2%
      Signed-off-by: default avatarJesper Dangaard Brouer <brouer@redhat.com>
      Cc: Christoph Lameter <cl@linux.com>
      Cc: Pekka Enberg <penberg@kernel.org>
      Cc: David Rientjes <rientjes@google.com>
      Cc: Joonsoo Kim <iamjoonsoo.kim@lge.com>
      Signed-off-by: default avatarAndrew Morton <akpm@linux-foundation.org>
      Signed-off-by: default avatarLinus Torvalds <torvalds@linux-foundation.org>
      3eed034d
    • Jesper Dangaard Brouer's avatar
      slub: initial bulk free implementation · fbd02630
      Jesper Dangaard Brouer authored
      
      
      This implements SLUB specific kmem_cache_free_bulk().  SLUB allocator now
      both have bulk alloc and free implemented.
      
      Choose to reenable local IRQs while calling slowpath __slab_free().  In
      worst case, where all objects hit slowpath call, the performance should
      still be faster than fallback function __kmem_cache_free_bulk(), because
      local_irq_{disable+enable} is very fast (7-cycles), while the fallback
      invokes this_cpu_cmpxchg() which is slightly slower (9-cycles).
      Nitpicking, this should be faster for N>=4, due to the entry cost of
      local_irq_{disable+enable}.
      
      Do notice that the save+restore variant is very expensive, this is key to
      why this optimization works.
      
      CPU: i7-4790K CPU @ 4.00GHz
       * local_irq_{disable,enable}:  7 cycles(tsc) - 1.821 ns
       * local_irq_{save,restore}  : 37 cycles(tsc) - 9.443 ns
      
      Measurements on CPU CPU i7-4790K @ 4.00GHz
      Baseline normal fastpath (alloc+free cost): 43 cycles(tsc) 10.834 ns
      
      Bulk- fallback                   - this-patch
        1 -  58 cycles(tsc) 14.542 ns  -  43 cycles(tsc) 10.811 ns  improved 25.9%
        2 -  50 cycles(tsc) 12.659 ns  -  27 cycles(tsc)  6.867 ns  improved 46.0%
        3 -  48 cycles(tsc) 12.168 ns  -  21 cycles(tsc)  5.496 ns  improved 56.2%
        4 -  47 cycles(tsc) 11.987 ns  -  24 cycles(tsc)  6.038 ns  improved 48.9%
        8 -  46 cycles(tsc) 11.518 ns  -  17 cycles(tsc)  4.280 ns  improved 63.0%
       16 -  45 cycles(tsc) 11.366 ns  -  17 cycles(tsc)  4.483 ns  improved 62.2%
       30 -  45 cycles(tsc) 11.433 ns  -  18 cycles(tsc)  4.531 ns  improved 60.0%
       32 -  75 cycles(tsc) 18.983 ns  -  58 cycles(tsc) 14.586 ns  improved 22.7%
       34 -  71 cycles(tsc) 17.940 ns  -  53 cycles(tsc) 13.391 ns  improved 25.4%
       48 -  80 cycles(tsc) 20.077 ns  -  65 cycles(tsc) 16.268 ns  improved 18.8%
       64 -  71 cycles(tsc) 17.799 ns  -  53 cycles(tsc) 13.440 ns  improved 25.4%
      128 -  91 cycles(tsc) 22.980 ns  -  79 cycles(tsc) 19.899 ns  improved 13.2%
      158 - 100 cycles(tsc) 25.241 ns  -  90 cycles(tsc) 22.732 ns  improved 10.0%
      250 - 102 cycles(tsc) 25.583 ns  -  95 cycles(tsc) 23.916 ns  improved  6.9%
      Signed-off-by: default avatarJesper Dangaard Brouer <brouer@redhat.com>
      Cc: Christoph Lameter <cl@linux.com>
      Cc: Pekka Enberg <penberg@kernel.org>
      Cc: David Rientjes <rientjes@google.com>
      Cc: Joonsoo Kim <iamjoonsoo.kim@lge.com>
      Signed-off-by: default avatarAndrew Morton <akpm@linux-foundation.org>
      Signed-off-by: default avatarLinus Torvalds <torvalds@linux-foundation.org>
      fbd02630
    • Jesper Dangaard Brouer's avatar
      slub: improve bulk alloc strategy · ebe909e0
      Jesper Dangaard Brouer authored
      
      
      Call slowpath __slab_alloc() from within the bulk loop, as the side-effect
      of this call likely repopulates c->freelist.
      
      Choose to reenable local IRQs while calling slowpath.
      
      Saving some optimizations for later.  E.g.  it is possible to extract
      parts of __slab_alloc() and avoid the unnecessary and expensive (37
      cycles) local_irq_{save,restore}.  For now, be happy calling
      __slab_alloc() this lower icache impact of this func and I don't have to
      worry about correctness.
      
      Measurements on CPU CPU i7-4790K @ 4.00GHz
      Baseline normal fastpath (alloc+free cost): 42 cycles(tsc) 10.601 ns
      
      Bulk- fallback                   - this-patch
        1 -  58 cycles(tsc) 14.516 ns  -  49 cycles(tsc) 12.459 ns  improved 15.5%
        2 -  51 cycles(tsc) 12.930 ns  -  38 cycles(tsc)  9.605 ns  improved 25.5%
        3 -  49 cycles(tsc) 12.274 ns  -  34 cycles(tsc)  8.525 ns  improved 30.6%
        4 -  48 cycles(tsc) 12.058 ns  -  32 cycles(tsc)  8.036 ns  improved 33.3%
        8 -  46 cycles(tsc) 11.609 ns  -  31 cycles(tsc)  7.756 ns  improved 32.6%
       16 -  45 cycles(tsc) 11.451 ns  -  32 cycles(tsc)  8.148 ns  improved 28.9%
       30 -  79 cycles(tsc) 19.865 ns  -  68 cycles(tsc) 17.164 ns  improved 13.9%
       32 -  76 cycles(tsc) 19.212 ns  -  66 cycles(tsc) 16.584 ns  improved 13.2%
       34 -  74 cycles(tsc) 18.600 ns  -  63 cycles(tsc) 15.954 ns  improved 14.9%
       48 -  88 cycles(tsc) 22.092 ns  -  77 cycles(tsc) 19.373 ns  improved 12.5%
       64 -  80 cycles(tsc) 20.043 ns  -  68 cycles(tsc) 17.188 ns  improved 15.0%
      128 -  99 cycles(tsc) 24.818 ns  -  89 cycles(tsc) 22.404 ns  improved 10.1%
      158 -  99 cycles(tsc) 24.977 ns  -  92 cycles(tsc) 23.089 ns  improved  7.1%
      250 - 106 cycles(tsc) 26.552 ns  -  99 cycles(tsc) 24.785 ns  improved  6.6%
      Signed-off-by: default avatarJesper Dangaard Brouer <brouer@redhat.com>
      Cc: Christoph Lameter <cl@linux.com>
      Cc: Pekka Enberg <penberg@kernel.org>
      Cc: David Rientjes <rientjes@google.com>
      Cc: Joonsoo Kim <iamjoonsoo.kim@lge.com>
      Signed-off-by: default avatarAndrew Morton <akpm@linux-foundation.org>
      Signed-off-by: default avatarLinus Torvalds <torvalds@linux-foundation.org>
      ebe909e0
    • Jesper Dangaard Brouer's avatar
      slub bulk alloc: extract objects from the per cpu slab · 994eb764
      Jesper Dangaard Brouer authored
      
      
      First piece: acceleration of retrieval of per cpu objects
      
      If we are allocating lots of objects then it is advantageous to disable
      interrupts and avoid the this_cpu_cmpxchg() operation to get these objects
      faster.
      
      Note that we cannot do the fast operation if debugging is enabled, because
      we would have to add extra code to do all the debugging checks.  And it
      would not be fast anyway.
      
      Note also that the requirement of having interrupts disabled avoids having
      to do processor flag operations.
      
      Allocate as many objects as possible in the fast way and then fall back to
      the generic implementation for the rest of the objects.
      
      Measurements on CPU CPU i7-4790K @ 4.00GHz
      Baseline normal fastpath (alloc+free cost): 42 cycles(tsc) 10.554 ns
      
      Bulk- fallback                   - this-patch
        1 -  57 cycles(tsc) 14.432 ns  -  48 cycles(tsc) 12.155 ns  improved 15.8%
        2 -  50 cycles(tsc) 12.746 ns  -  37 cycles(tsc)  9.390 ns  improved 26.0%
        3 -  48 cycles(tsc) 12.180 ns  -  33 cycles(tsc)  8.417 ns  improved 31.2%
        4 -  48 cycles(tsc) 12.015 ns  -  32 cycles(tsc)  8.045 ns  improved 33.3%
        8 -  46 cycles(tsc) 11.526 ns  -  30 cycles(tsc)  7.699 ns  improved 34.8%
       16 -  45 cycles(tsc) 11.418 ns  -  32 cycles(tsc)  8.205 ns  improved 28.9%
       30 -  80 cycles(tsc) 20.246 ns  -  73 cycles(tsc) 18.328 ns  improved  8.8%
       32 -  79 cycles(tsc) 19.946 ns  -  72 cycles(tsc) 18.208 ns  improved  8.9%
       34 -  78 cycles(tsc) 19.659 ns  -  71 cycles(tsc) 17.987 ns  improved  9.0%
       48 -  86 cycles(tsc) 21.516 ns  -  82 cycles(tsc) 20.566 ns  improved  4.7%
       64 -  93 cycles(tsc) 23.423 ns  -  89 cycles(tsc) 22.480 ns  improved  4.3%
      128 - 100 cycles(tsc) 25.170 ns  -  99 cycles(tsc) 24.871 ns  improved  1.0%
      158 - 102 cycles(tsc) 25.549 ns  - 101 cycles(tsc) 25.375 ns  improved  1.0%
      250 - 101 cycles(tsc) 25.344 ns  - 100 cycles(tsc) 25.182 ns  improved  1.0%
      Signed-off-by: default avatarChristoph Lameter <cl@linux.com>
      Signed-off-by: default avatarJesper Dangaard Brouer <brouer@redhat.com>
      Cc: Pekka Enberg <penberg@kernel.org>
      Cc: David Rientjes <rientjes@google.com>
      Cc: Joonsoo Kim <iamjoonsoo.kim@lge.com>
      Signed-off-by: default avatarAndrew Morton <akpm@linux-foundation.org>
      Signed-off-by: default avatarLinus Torvalds <torvalds@linux-foundation.org>
      994eb764
    • Christoph Lameter's avatar
      slab: infrastructure for bulk object allocation and freeing · 484748f0
      Christoph Lameter authored
      
      
      Add the basic infrastructure for alloc/free operations on pointer arrays.
      It includes a generic function in the common slab code that is used in
      this infrastructure patch to create the unoptimized functionality for slab
      bulk operations.
      
      Allocators can then provide optimized allocation functions for situations
      in which large numbers of objects are needed.  These optimization may
      avoid taking locks repeatedly and bypass metadata creation if all objects
      in slab pages can be used to provide the objects required.
      
      Allocators can extend the skeletons provided and add their own code to the
      bulk alloc and free functions.  They can keep the generic allocation and
      freeing and just fall back to those if optimizations would not work (like
      for example when debugging is on).
      Signed-off-by: default avatarChristoph Lameter <cl@linux.com>
      Signed-off-by: default avatarJesper Dangaard Brouer <brouer@redhat.com>
      Cc: Pekka Enberg <penberg@kernel.org>
      Cc: David Rientjes <rientjes@google.com>
      Cc: Joonsoo Kim <iamjoonsoo.kim@lge.com>
      Signed-off-by: default avatarAndrew Morton <akpm@linux-foundation.org>
      Signed-off-by: default avatarLinus Torvalds <torvalds@linux-foundation.org>
      484748f0
    • Jesper Dangaard Brouer's avatar
      slub: fix spelling succedd to succeed · 2ae44005
      Jesper Dangaard Brouer authored
      
      
      With this patchset the SLUB allocator now has both bulk alloc and free
      implemented.
      
      This patchset mostly optimizes the "fastpath" where objects are available
      on the per CPU fastpath page.  This mostly amortize the less-heavy
      none-locked cmpxchg_double used on fastpath.
      
      The "fallback" bulking (e.g __kmem_cache_free_bulk) provides a good basis
      for comparison.  Measurements[1] of the fallback functions
      __kmem_cache_{free,alloc}_bulk have been copied from slab_common.c and
      forced "noinline" to force a function call like slab_common.c.
      
      Measurements on CPU CPU i7-4790K @ 4.00GHz
      Baseline normal fastpath (alloc+free cost): 42 cycles(tsc) 10.601 ns
      
      Measurements last-patch with disabled debugging:
      
      Bulk- fallback                   - this-patch
        1 -  57 cycles(tsc) 14.448 ns  -  44 cycles(tsc) 11.236 ns  improved 22.8%
        2 -  51 cycles(tsc) 12.768 ns  -  28 cycles(tsc)  7.019 ns  improved 45.1%
        3 -  48 cycles(tsc) 12.232 ns  -  22 cycles(tsc)  5.526 ns  improved 54.2%
        4 -  48 cycles(tsc) 12.025 ns  -  19 cycles(tsc)  4.786 ns  improved 60.4%
        8 -  46 cycles(tsc) 11.558 ns  -  18 cycles(tsc)  4.572 ns  improved 60.9%
       16 -  45 cycles(tsc) 11.458 ns  -  18 cycles(tsc)  4.658 ns  improved 60.0%
       30 -  45 cycles(tsc) 11.499 ns  -  18 cycles(tsc)  4.568 ns  improved 60.0%
       32 -  79 cycles(tsc) 19.917 ns  -  65 cycles(tsc) 16.454 ns  improved 17.7%
       34 -  78 cycles(tsc) 19.655 ns  -  63 cycles(tsc) 15.932 ns  improved 19.2%
       48 -  68 cycles(tsc) 17.049 ns  -  50 cycles(tsc) 12.506 ns  improved 26.5%
       64 -  80 cycles(tsc) 20.009 ns  -  63 cycles(tsc) 15.929 ns  improved 21.3%
      128 -  94 cycles(tsc) 23.749 ns  -  86 cycles(tsc) 21.583 ns  improved  8.5%
      158 -  97 cycles(tsc) 24.299 ns  -  90 cycles(tsc) 22.552 ns  improved  7.2%
      250 - 102 cycles(tsc) 25.681 ns  -  98 cycles(tsc) 24.589 ns  improved  3.9%
      
      Benchmarking shows impressive improvements in the "fastpath" with a small
      number of objects in the working set.  Once the working set increases,
      resulting in activating the "slowpath" (that contains the heavier locked
      cmpxchg_double) the improvement decreases.
      
      I'm currently working on also optimizing the "slowpath" (as network stack
      use-case hits this), but this patchset should provide a good foundation
      for further improvements.  Rest of my patch queue in this area needs some
      more work, but preliminary results are good.  I'm attending Netfilter
      Workshop[2] next week, and I'll hopefully return working on further
      improvements in this area.
      
      This patch (of 6):
      
      s/succedd/succeed/
      Signed-off-by: default avatarJesper Dangaard Brouer <brouer@redhat.com>
      Cc: Christoph Lameter <cl@linux.com>
      Cc: Pekka Enberg <penberg@kernel.org>
      Cc: David Rientjes <rientjes@google.com>
      Cc: Joonsoo Kim <iamjoonsoo.kim@lge.com>
      Signed-off-by: default avatarAndrew Morton <akpm@linux-foundation.org>
      Signed-off-by: default avatarLinus Torvalds <torvalds@linux-foundation.org>
      2ae44005
    • Ulrich Obergfell's avatar
      watchdog: rename watchdog_suspend() and watchdog_resume() · ec6a9066
      Ulrich Obergfell authored
      
      
      Rename watchdog_suspend() to lockup_detector_suspend() and
      watchdog_resume() to lockup_detector_resume() to avoid confusion with the
      watchdog subsystem and to be consistent with the existing name
      lockup_detector_init().
      
      Also provide comment blocks to explain the watchdog_running and
      watchdog_suspended variables and their relationship.
      Signed-off-by: default avatarUlrich Obergfell <uobergfe@redhat.com>
      Reviewed-by: default avatarAaron Tomlin <atomlin@redhat.com>
      Cc: Guenter Roeck <linux@roeck-us.net>
      Cc: Don Zickus <dzickus@redhat.com>
      Cc: Ulrich Obergfell <uobergfe@redhat.com>
      Cc: Jiri Olsa <jolsa@kernel.org>
      Cc: Michal Hocko <mhocko@suse.cz>
      Cc: Stephane Eranian <eranian@google.com>
      Cc: Chris Metcalf <cmetcalf@ezchip.com>
      Cc: Frederic Weisbecker <fweisbec@gmail.com>
      Cc: Peter Zijlstra <a.p.zijlstra@chello.nl>
      Cc: Ingo Molnar <mingo@redhat.com>
      Signed-off-by: default avatarAndrew Morton <akpm@linux-foundation.org>
      Signed-off-by: default avatarLinus Torvalds <torvalds@linux-foundation.org>
      ec6a9066
    • Ulrich Obergfell's avatar
      watchdog: use suspend/resume interface in fixup_ht_bug() · 999bbe49
      Ulrich Obergfell authored
      
      
      Remove watchdog_nmi_disable_all() and watchdog_nmi_enable_all() since
      these functions are no longer needed.  If a subsystem has a need to
      deactivate the watchdog temporarily, it should utilize the
      watchdog_suspend() and watchdog_resume() functions.
      
      [akpm@linux-foundation.org: fix build with CONFIG_LOCKUP_DETECTOR=m]
      Signed-off-by: default avatarUlrich Obergfell <uobergfe@redhat.com>
      Reviewed-by: default avatarAaron Tomlin <atomlin@redhat.com>
      Cc: Guenter Roeck <linux@roeck-us.net>
      Cc: Don Zickus <dzickus@redhat.com>
      Cc: Ulrich Obergfell <uobergfe@redhat.com>
      Cc: Jiri Olsa <jolsa@kernel.org>
      Cc: Michal Hocko <mhocko@suse.cz>
      Cc: Stephane Eranian <eranian@google.com>
      Cc: Chris Metcalf <cmetcalf@ezchip.com>
      Cc: Frederic Weisbecker <fweisbec@gmail.com>
      Cc: Peter Zijlstra <a.p.zijlstra@chello.nl>
      Cc: Ingo Molnar <mingo@redhat.com>
      Signed-off-by: default avatarAndrew Morton <akpm@linux-foundation.org>
      Signed-off-by: default avatarLinus Torvalds <torvalds@linux-foundation.org>
      999bbe49
    • Ulrich Obergfell's avatar
      watchdog: use park/unpark functions in update_watchdog_all_cpus() · d4bdd0b2
      Ulrich Obergfell authored
      
      
      Remove update_watchdog() and restart_watchdog_hrtimer() since these
      functions are no longer needed.  Changes of parameters such as the sample
      period are honored at the time when the watchdog threads are being
      unparked.
      Signed-off-by: default avatarUlrich Obergfell <uobergfe@redhat.com>
      Reviewed-by: default avatarAaron Tomlin <atomlin@redhat.com>
      Cc: Guenter Roeck <linux@roeck-us.net>
      Cc: Don Zickus <dzickus@redhat.com>
      Cc: Ulrich Obergfell <uobergfe@redhat.com>
      Cc: Jiri Olsa <jolsa@kernel.org>
      Cc: Michal Hocko <mhocko@suse.cz>
      Cc: Stephane Eranian <eranian@google.com>
      Cc: Chris Metcalf <cmetcalf@ezchip.com>
      Cc: Frederic Weisbecker <fweisbec@gmail.com>
      Cc: Peter Zijlstra <a.p.zijlstra@chello.nl>
      Cc: Ingo Molnar <mingo@redhat.com>
      Signed-off-by: default avatarAndrew Morton <akpm@linux-foundation.org>
      Signed-off-by: default avatarLinus Torvalds <torvalds@linux-foundation.org>
      d4bdd0b2
    • Ulrich Obergfell's avatar
      watchdog: introduce watchdog_suspend() and watchdog_resume() · 8c073d27
      Ulrich Obergfell authored
      
      
      This interface can be utilized to deactivate the hard and soft lockup
      detector temporarily.  Callers are expected to minimize the duration of
      deactivation.  Multiple deactivations are allowed to occur in parallel but
      should be rare in practice.
      
      [akpm@linux-foundation.org: remove unneeded static initialization]
      Signed-off-by: default avatarUlrich Obergfell <uobergfe@redhat.com>
      Reviewed-by: default avatarAaron Tomlin <atomlin@redhat.com>
      Cc: Guenter Roeck <linux@roeck-us.net>
      Cc: Don Zickus <dzickus@redhat.com>
      Cc: Ulrich Obergfell <uobergfe@redhat.com>
      Cc: Jiri Olsa <jolsa@kernel.org>
      Cc: Michal Hocko <mhocko@suse.cz>
      Cc: Stephane Eranian <eranian@google.com>
      Cc: Chris Metcalf <cmetcalf@ezchip.com>
      Cc: Frederic Weisbecker <fweisbec@gmail.com>
      Cc: Peter Zijlstra <a.p.zijlstra@chello.nl>
      Cc: Ingo Molnar <mingo@redhat.com>
      Signed-off-by: default avatarAndrew Morton <akpm@linux-foundation.org>
      Signed-off-by: default avatarLinus Torvalds <torvalds@linux-foundation.org>
      8c073d27
    • Ulrich Obergfell's avatar
      watchdog: introduce watchdog_park_threads() and watchdog_unpark_threads() · 81a4beef
      Ulrich Obergfell authored
      Originally watchdog_nmi_enable(cpu) and watchdog_nmi_disable(cpu) were
      only called in watchdog thread context.  However, the following commits
      utilize these functions outside of watchdog thread context too.
      
        commit 9809b18f
        Author: Michal Hocko <mhocko@suse.cz>
        Date:   Tue Sep 24 15:27:30 2013 -0700
      
            watchdog: update watchdog_thresh properly
      
        commit b3738d29
        Author: Stephane Eranian <eranian@google.com>
        Date:   Mon Nov 17 20:07:03 2014 +0100
      
            watchdog: Add watchdog enable/disable all functions
      
      Hence, it is now possible that these functions execute concurrently with
      the same 'cpu' argument.  This concurrency is problematic because per-cpu
      'watchdog_ev' can be accessed/modified without adequate synchronization.
      
      The patch series aims to address the above problem.  However, instead of
      introducing locks to protect per-cpu 'watchdog_ev' a different approach is
      taken: Invoke these functions by parking and unparking the watchdog
      threads (to ensure they are always called in watchdog thread context).
      
        static struct smp_hotplug_thread watchdog_threads = {
                 ...
                .park   = watchdog_disable, // calls watchdog_nmi_disable()
                .unpark = watchdog_enable,  // calls watchdog_nmi_enable()
        };
      
      Both previously mentioned commits call these functions in a similar way
      and thus in principle contain some duplicate code.  The patch series also
      avoids this duplication by providing a commonly usable mechanism.
      
      - Patch 1/4 introduces the watchdog_{park|unpark}_threads functions that
        park/unpark all watchdog threads specified in 'watchdog_cpumask'. They
        are intended to be called inside of kernel/watchdog.c only.
      
      - Patch 2/4 introduces the watchdog_{suspend|resume} functions which can
        be utilized by external callers to deactivate the hard and soft lockup
        detector temporarily.
      
      - Patch 3/4 utilizes watchdog_{park|unpark}_threads to replace some code
        that was introduced by commit 9809b18f.
      
      - Patch 4/4 utilizes watchdog_{suspend|resume} to replace some code that
        was introduced by commit b3738d29
      
      .
      
      A few corner cases should be mentioned here for completeness.
      
      - kthread_park() of watchdog/N could hang if cpu N is already locked up.
        However, if watchdog is enabled the lockup will be detected anyway.
      
      - kthread_unpark() of watchdog/N could hang if cpu N got locked up after
        kthread_park(). The occurrence of this scenario should be _very_ rare
        in practice, in particular because it is not expected that temporary
        deactivation will happen frequently, and if it happens at all it is
        expected that the duration of deactivation will be short.
      
      This patch (of 4): introduce watchdog_park_threads() and watchdog_unpark_threads()
      
      These functions are intended to be used only from inside kernel/watchdog.c
      to park/unpark all watchdog threads that are specified in
      watchdog_cpumask.
      Signed-off-by: default avatarUlrich Obergfell <uobergfe@redhat.com>
      Reviewed-by: default avatarAaron Tomlin <atomlin@redhat.com>
      Cc: Guenter Roeck <linux@roeck-us.net>
      Cc: Don Zickus <dzickus@redhat.com>
      Cc: Ulrich Obergfell <uobergfe@redhat.com>
      Cc: Jiri Olsa <jolsa@kernel.org>
      Cc: Michal Hocko <mhocko@suse.cz>
      Cc: Stephane Eranian <eranian@google.com>
      Cc: Chris Metcalf <cmetcalf@ezchip.com>
      Cc: Frederic Weisbecker <fweisbec@gmail.com>
      Cc: Peter Zijlstra <a.p.zijlstra@chello.nl>
      Cc: Ingo Molnar <mingo@redhat.com>
      Signed-off-by: default avatarAndrew Morton <akpm@linux-foundation.org>
      Signed-off-by: default avatarLinus Torvalds <torvalds@linux-foundation.org>
      81a4beef
    • Guenter Roeck's avatar
      kernel/watchdog: move NMI function header declarations from watchdog.h to nmi.h · aacfbe6a
      Guenter Roeck authored
      
      
      The kernel's NMI watchdog has nothing to do with the watchdog subsystem.
      Its header declarations should be in linux/nmi.h, not linux/watchdog.h.
      
      The code provided two sets of dummy functions if HARDLOCKUP_DETECTOR is
      not configured, one in the include file and one in kernel/watchdog.c.
      Remove the dummy functions from kernel/watchdog.c and use those from the
      include file.
      Signed-off-by: default avatarGuenter Roeck <linux@roeck-us.net>
      Cc: Stephane Eranian <eranian@google.com>
      Cc: Peter Zijlstra (Intel) <peterz@infradead.org>
      Cc: Ingo Molnar <mingo@kernel.org>
      Cc: Don Zickus <dzickus@redhat.com>
      Signed-off-by: default avatarAndrew Morton <akpm@linux-foundation.org>
      Signed-off-by: default avatarLinus Torvalds <torvalds@linux-foundation.org>
      aacfbe6a
    • Frederic Weisbecker's avatar
      watchdog: simplify housekeeping affinity with the appropriate mask · 314b08ff
      Frederic Weisbecker authored
      
      
      housekeeping_mask gathers all the CPUs that aren't part of the nohz_full
      set.  This is exactly what we want the watchdog to be affine to without
      the need to use complicated cpumask operations.
      Signed-off-by: default avatarFrederic Weisbecker <fweisbec@gmail.com>
      Reviewed-by: default avatarChris Metcalf <cmetcalf@ezchip.com>
      Cc: Thomas Gleixner <tglx@linutronix.de>
      Cc: Chris Metcalf <cmetcalf@ezchip.com>
      Cc: Don Zickus <dzickus@redhat.com>
      Cc: Peter Zijlstra <peterz@infradead.org>
      Cc: Ulrich Obergfell <uobergfe@redhat.com>
      Signed-off-by: default avatarAndrew Morton <akpm@linux-foundation.org>
      Signed-off-by: default avatarLinus Torvalds <torvalds@linux-foundation.org>
      314b08ff
    • Frederic Weisbecker's avatar
      smpboot: allow passing the cpumask on per-cpu thread registration · 230ec939
      Frederic Weisbecker authored
      
      
      It makes the registration cheaper and simpler for the smpboot per-cpu
      kthread users that don't need to always update the cpumask after threads
      creation.
      
      [sfr@canb.auug.org.au: fix for allow passing the cpumask on per-cpu thread registration]
      Signed-off-by: default avatarFrederic Weisbecker <fweisbec@gmail.com>
      Reviewed-by: default avatarChris Metcalf <cmetcalf@ezchip.com>
      Reviewed-by: default avatarThomas Gleixner <tglx@linutronix.de>
      Cc: Chris Metcalf <cmetcalf@ezchip.com>
      Cc: Don Zickus <dzickus@redhat.com>
      Cc: Peter Zijlstra <peterz@infradead.org>
      Cc: Ulrich Obergfell <uobergfe@redhat.com>
      Signed-off-by: default avatarStephen Rothwell <sfr@canb.auug.org.au>
      Signed-off-by: default avatarAndrew Morton <akpm@linux-foundation.org>
      Signed-off-by: default avatarLinus Torvalds <torvalds@linux-foundation.org>
      230ec939
    • Frederic Weisbecker's avatar
      smpboot: make cleanup to mirror setup · 3dd08c0c
      Frederic Weisbecker authored
      
      
      The per-cpu kthread cleanup() callback is the mirror of the setup()
      callback.  When the per-cpu kthread is started, it first calls setup()
      to initialize the resources which are then released by cleanup() when
      the kthread exits.
      
      Now since the introduction of a per-cpu kthread cpumask, the kthreads
      excluded by the cpumask on boot may happen to be parked immediately
      after their creation without taking the setup() stage, waiting to be
      asked to unpark to do so.  Then when smpboot_unregister_percpu_thread()
      is later called, the kthread is stopped without having ever called
      setup().
      
      But this triggers a bug as the kthread unconditionally calls cleanup()
      on exit but this doesn't mirror any setup().  Thus the kernel crashes
      because we try to free resources that haven't been initialized, as in
      the watchdog case:
      
          WATCHDOG disable 0
          WATCHDOG disable 1
          WATCHDOG disable 2
          BUG: unable to handle kernel NULL pointer dereference at           (null)
          IP: hrtimer_active+0x26/0x60
          [...]
          Call Trace:
            hrtimer_try_to_cancel+0x1c/0x280
            hrtimer_cancel+0x1d/0x30
            watchdog_disable+0x56/0x70
            watchdog_cleanup+0xe/0x10
            smpboot_thread_fn+0x23c/0x2c0
            kthread+0xf8/0x110
            ret_from_fork+0x3f/0x70
      
      This bug is currently masked with explicit kthread unparking before
      kthread_stop() on smpboot_destroy_threads(). This forces a call to
      setup() and then unpark().
      
      We could fix this by unconditionally calling setup() on kthread entry.
      But setup() isn't always cheap.  In the case of watchdog it launches
      hrtimer, perf events, etc...  So we may as well like to skip it if there
      are chances the kthread will never be used, as in a reduced cpumask value.
      
      So let's simply do a state machine check before calling cleanup() that
      makes sure setup() has been called before mirroring it.
      
      And remove the nasty hack workaround.
      Signed-off-by: default avatarFrederic Weisbecker <fweisbec@gmail.com>
      Reviewed-by: default avatarChris Metcalf <cmetcalf@ezchip.com>
      Reviewed-by: default avatarThomas Gleixner <tglx@linutronix.de>
      Cc: Chris Metcalf <cmetcalf@ezchip.com>
      Cc: Don Zickus <dzickus@redhat.com>
      Cc: Peter Zijlstra <peterz@infradead.org>
      Cc: Ulrich Obergfell <uobergfe@redhat.com>
      Signed-off-by: default avatarAndrew Morton <akpm@linux-foundation.org>
      Signed-off-by: default avatarLinus Torvalds <torvalds@linux-foundation.org>
      3dd08c0c
    • Frederic Weisbecker's avatar
      smpboot: fix memory leak on error handling · 5869b506
      Frederic Weisbecker authored
      
      
      The cpumask is allocated before threads get created. If the latter step
      fails, we need to free the cpumask.
      Signed-off-by: default avatarFrederic Weisbecker <fweisbec@gmail.com>
      Reviewed-by: default avatarChris Metcalf <cmetcalf@ezchip.com>
      Reviewed-by: default avatarThomas Gleixner <tglx@linutronix.de>
      Cc: Chris Metcalf <cmetcalf@ezchip.com>
      Cc: Don Zickus <dzickus@redhat.com>
      Cc: Peter Zijlstra <peterz@infradead.org>
      Cc: Ulrich Obergfell <uobergfe@redhat.com>
      Signed-off-by: default avatarAndrew Morton <akpm@linux-foundation.org>
      Signed-off-by: default avatarLinus Torvalds <torvalds@linux-foundation.org>
      5869b506