1. 17 Apr, 2013 12 commits
  2. 16 Apr, 2013 6 commits
  3. 15 Apr, 2013 9 commits
  4. 14 Apr, 2013 11 commits
  5. 13 Apr, 2013 2 commits
    • Suleiman Souhlal's avatar
      vfs: Revert spurious fix to spinning prevention in prune_icache_sb · 5b55d708
      Suleiman Souhlal authored
      Revert commit 62a3ddef
      
       ("vfs: fix spinning prevention in prune_icache_sb").
      
      This commit doesn't look right: since we are looking at the tail of the
      list (sb->s_inode_lru.prev) if we want to skip an inode, we should put
      it back at the head of the list instead of the tail, otherwise we will
      keep spinning on it.
      
      Discovered when investigating why prune_icache_sb came top in perf
      reports of a swapping load.
      Signed-off-by: default avatarSuleiman Souhlal <suleiman@google.com>
      Signed-off-by: default avatarHugh Dickins <hughd@google.com>
      Cc: stable@vger.kernel.org # v3.2+
      Signed-off-by: default avatarLinus Torvalds <torvalds@linux-foundation.org>
      5b55d708
    • Linus Torvalds's avatar
      kobject: fix kset_find_obj() race with concurrent last kobject_put() · a49b7e82
      Linus Torvalds authored
      Anatol Pomozov identified a race condition that hits module unloading
      and re-loading.  To quote Anatol:
      
       "This is a race codition that exists between kset_find_obj() and
        kobject_put().  kset_find_obj() might return kobject that has refcount
        equal to 0 if this kobject is freeing by kobject_put() in other
        thread.
      
        Here is timeline for the crash in case if kset_find_obj() searches for
        an object tht nobody holds and other thread is doing kobject_put() on
        the same kobject:
      
          THREAD A (calls kset_find_obj())     THREAD B (calls kobject_put())
          splin_lock()
                                               atomic_dec_return(kobj->kref), counter gets zero here
                                               ... starts kobject cleanup ....
                                               spin_lock() // WAIT thread A in kobj_kset_leave()
          iterate over kset->list
          atomic_inc(kobj->kref) (counter becomes 1)
          spin_unlock()
                                               spin_lock() // taken
                                               // it does not know that thread A increased counter so it
                                               remove obj from list
                                               spin_unlock()
                                               vfree(module) // frees module object with containing kobj
      
          // kobj points to freed memory area!!
          kobject_put(kobj) // OOPS!!!!
      
        The race above happens because module.c tries to use kset_find_obj()
        when somebody unloads module.  The module.c code was introduced in
        commit 6494a93d
      
      "
      
      Anatol supplied a patch specific for module.c that worked around the
      problem by simply not using kset_find_obj() at all, but rather than make
      a local band-aid, this just fixes kset_find_obj() to be thread-safe
      using the proper model of refusing the get a new reference if the
      refcount has already dropped to zero.
      
      See examples of this proper refcount handling not only in the kref
      documentation, but in various other equivalent uses of this pattern by
      grepping for atomic_inc_not_zero().
      
      [ Side note: the module race does indicate that module loading and
        unloading is not properly serialized wrt sysfs information using the
        module mutex.  That may require further thought, but this is the
        correct fix at the kobject layer regardless. ]
      Reported-analyzed-and-tested-by: default avatarAnatol Pomozov <anatol.pomozov@gmail.com>
      Cc: Greg Kroah-Hartman <gregkh@linuxfoundation.org>
      Cc: Al Viro <viro@zeniv.linux.org.uk>
      Cc: stable@vger.kernel.org
      Signed-off-by: default avatarLinus Torvalds <torvalds@linux-foundation.org>
      a49b7e82