1. 15 Mar, 2013 37 commits
    • Steven Rostedt (Red Hat)'s avatar
      tracing: Prevent deleting instances when they are being read · a695cb58
      Steven Rostedt (Red Hat) authored
      
      
      Add a ref count to the trace_array structure and prevent removal
      of instances that have open descriptors.
      Signed-off-by: default avatarSteven Rostedt <rostedt@goodmis.org>
      a695cb58
    • Steven Rostedt (Red Hat)'s avatar
      tracing: Add per_cpu directory into tracing instances · 121aaee7
      Steven Rostedt (Red Hat) authored
      
      
      Add the per_cpu directory to the created tracing instances:
      
        cd /sys/kernel/debug/tracing/instances
        mkdir foo
        ls foo/per_cpu/cpu0
      buffer_size_kb	snapshot_raw  trace	  trace_pipe_raw
      snapshot	stats	      trace_pipe
      Signed-off-by: default avatarSteven Rostedt <rostedt@goodmis.org>
      121aaee7
    • Steven Rostedt (Red Hat)'s avatar
      tracing: Add snapshot feature to instances · ce9bae55
      Steven Rostedt (Red Hat) authored
      
      
      Add the "snapshot" file to the the multi-buffer instances.
      
        cd /sys/kernel/debug/tracing/instances
        mkdir foo
        ls foo
      buffer_size_kb  buffer_total_size_kb  events  free_buffer  set_event
      snapshot  trace  trace_clock  trace_marker  trace_options  trace_pipe
      tracing_on
        cat foo/snapshot
       # tracer: nop
       #
       #
       # * Snapshot is freed *
       #
       # Snapshot commands:
       # echo 0 > snapshot : Clears and frees snapshot buffer
       # echo 1 > snapshot : Allocates snapshot buffer, if not already allocated.
       #                      Takes a snapshot of the main buffer.
       # echo 2 > snapshot : Clears snapshot buffer (but does not allocate)
       #                      (Doesn't have to be '2' works with any number that
       #                       is not a '0' or '1')
      Signed-off-by: default avatarSteven Rostedt <rostedt@goodmis.org>
      ce9bae55
    • Steven Rostedt (Red Hat)'s avatar
      tracing: Consolidate buffer allocation code · 737223fb
      Steven Rostedt (Red Hat) authored
      
      
      There's a bit of duplicate code in creating the trace buffers for
      the normal trace buffer and the max trace buffer among the instances
      and the main global_trace. This code can be consolidated and cleaned
      up a bit making the code cleaner and more readable as well as less
      duplication.
      Signed-off-by: default avatarSteven Rostedt <rostedt@goodmis.org>
      737223fb
    • Steven Rostedt (Red Hat)'s avatar
      tracing: Have trace_array keep track if snapshot buffer is allocated · 45ad21ca
      Steven Rostedt (Red Hat) authored
      
      
      The snapshot buffer belongs to the trace array not the tracer that is
      running. The trace array should be the data structure that keeps track
      of whether or not the snapshot buffer is allocated, not the tracer
      desciptor. Having the trace array keep track of it makes modifications
      so much easier.
      Signed-off-by: default avatarSteven Rostedt <rostedt@goodmis.org>
      45ad21ca
    • Steven Rostedt (Red Hat)'s avatar
      tracing: Add snapshot_raw to extract the raw data from snapshot · 6de58e62
      Steven Rostedt (Red Hat) authored
      
      
      Add a 'snapshot_raw' per_cpu file that allows tools to read the raw
      binary data of the snapshot buffer.
      Signed-off-by: default avatarSteven Rostedt <rostedt@goodmis.org>
      6de58e62
    • Steven Rostedt (Red Hat)'s avatar
      tracing: Add config option to allow snapshot to swap per cpu · 0b85ffc2
      Steven Rostedt (Red Hat) authored
      
      
      When the preempt or irq latency tracers are enabled, they require
      the ring buffer to be able to swap the per cpu sub buffers between
      two main buffers. This adds a slight overhead to tracing as the
      trace recording needs to perform some checks to synchronize
      between recording and swaps that might be happening on other CPUs.
      
      The config RING_BUFFER_ALLOW_SWAP is set when a user of the ring
      buffer needs the "swap cpu" feature, otherwise the extra checks
      are not implemented and removed from the tracing overhead.
      
      The snapshot feature will swap per CPU if the RING_BUFFER_ALLOW_SWAP
      config is set. But that only gets set by things like OPROFILE
      and the irqs and preempt latency tracers.
      
      This config is added to let the user decide to include this feature
      with the snapshot agnostic from whether or not another user of
      the ring buffer sets this config.
      Signed-off-by: default avatarSteven Rostedt <rostedt@goodmis.org>
      0b85ffc2
    • Steven Rostedt (Red Hat)'s avatar
      tracing: Add snapshot in the per_cpu trace directories · f1affcaa
      Steven Rostedt (Red Hat) authored
      
      
      Add the snapshot file into the per_cpu tracing directories to allow
      them to be read for an individual cpu. This also allows to clear
      an individual cpu from the snapshot buffer.
      
      If the kernel allows it (CONFIG_RING_BUFFER_ALLOW_SWAP is set), then
      echoing in '1' into one of the per_cpu snapshot files will do an
      individual cpu buffer swap instead of the entire file.
      
      Cc: Hiraku Toyooka <hiraku.toyooka.gu@hitachi.com>
      Signed-off-by: default avatarSteven Rostedt <rostedt@goodmis.org>
      f1affcaa
    • Steven Rostedt (Red Hat)'s avatar
      tracing: Consolidate max_tr into main trace_array structure · 12883efb
      Steven Rostedt (Red Hat) authored
      
      
      Currently, the way the latency tracers and snapshot feature works
      is to have a separate trace_array called "max_tr" that holds the
      snapshot buffer. For latency tracers, this snapshot buffer is used
      to swap the running buffer with this buffer to save the current max
      latency.
      
      The only items needed for the max_tr is really just a copy of the buffer
      itself, the per_cpu data pointers, the time_start timestamp that states
      when the max latency was triggered, and the cpu that the max latency
      was triggered on. All other fields in trace_array are unused by the
      max_tr, making the max_tr mostly bloat.
      
      This change removes the max_tr completely, and adds a new structure
      called trace_buffer, that holds the buffer pointer, the per_cpu data
      pointers, the time_start timestamp, and the cpu where the latency occurred.
      
      The trace_array, now has two trace_buffers, one for the normal trace and
      one for the max trace or snapshot. By doing this, not only do we remove
      the bloat from the max_trace but the instances of traces can now use
      their own snapshot feature and not have just the top level global_trace have
      the snapshot feature and latency tracers for itself.
      Signed-off-by: default avatarSteven Rostedt <rostedt@goodmis.org>
      12883efb
    • Steven Rostedt (Red Hat)'s avatar
      tracing: Enable snapshot when any latency tracer is enabled · 22cffc2b
      Steven Rostedt (Red Hat) authored
      
      
      The snapshot utility is extremely useful, and does not add any more
      overhead in memory when another latency tracer is enabled. They use
      the snapshot underneath. There's no reason to hide the snapshot file
      when a latency tracer has been enabled in the kernel.
      
      If any of the latency tracers (irq, preempt or wakeup) is enabled
      then also select the snapshot facility.
      
      Note, snapshot can be enabled without the latency tracers enabled.
      Signed-off-by: default avatarSteven Rostedt <rostedt@goodmis.org>
      22cffc2b
    • Steven Rostedt (Red Hat)'s avatar
      tracing: Clear all trace buffers when unloaded module event was used · 873c642f
      Steven Rostedt (Red Hat) authored
      
      
      Currently we do not know what buffer a module event was enabled in.
      On unload, it is safest to clear all buffer instances, not just the
      top level buffer.
      
      Todo: Clear only the buffer that the event was used in. The
      infrastructure is there to do this, but it makes the code a bit
      more complex. Lets get the current code vetted before we add that.
      Signed-off-by: default avatarSteven Rostedt <rostedt@goodmis.org>
      873c642f
    • Steven Rostedt (Red Hat)'s avatar
      tracing: Only clear trace buffer on module unload if event was traced · 575380da
      Steven Rostedt (Red Hat) authored
      
      
      Currently, when a module with events is unloaded, the trace buffer is
      cleared. This is just a safety net in case the module might have some
      strange callback when its event is outputted. But there's no reason
      to reset the buffer if the module didn't have any of its events traced.
      
      Add a flag to the event "call" structure called WAS_ENABLED and gets set
      when the event is ever enabled, and this flag never gets cleared. When a
      module gets unloaded, if any of its events have this flag set, then the
      trace buffer will get cleared.
      Signed-off-by: default avatarSteven Rostedt <rostedt@goodmis.org>
      575380da
    • Steven Rostedt (Red Hat)'s avatar
      tracing: Add comment for trace event flag IGNORE_ENABLE · 2a30c11f
      Steven Rostedt (Red Hat) authored
      
      
      All the trace event flags have comments but the IGNORE_ENABLE flag
      which is set for ftrace internal events that should not be enabled
      via the debugfs "enable" file. That is, if the top level enable file
      is set, it will enable all events. It use to just check the ftrace
      event call descriptor "reg" field and skip those whithout it, but now
      some ftrace internal events have a reg field but still need to be
      skipped. The flag was created to ignore those events.
      
      Now document it.
      Signed-off-by: default avatarSteven Rostedt <rostedt@goodmis.org>
      2a30c11f
    • Steven Rostedt (Red Hat)'s avatar
      ring-buffer: Init waitqueue for blocked readers · f1dc6725
      Steven Rostedt (Red Hat) authored
      
      
      The move of blocked readers to the ring buffer left out the
      init of the wait queue that is used. Tests missed this due to running
      stress tests against the buffers, which didn't allow for any
      readers to end up waiting. Running a simple read and wait triggered
      a bug.
      Signed-off-by: default avatarSteven Rostedt <rostedt@goodmis.org>
      f1dc6725
    • Li Zefan's avatar
      tracing: Fix some section mismatch warnings · 523c8113
      Li Zefan authored
      As we've added __init annotation to field-defining functions, we should
      add __refdata annotation to event_call variables, which reference those
      functions.
      
      Link: http://lkml.kernel.org/r/51343C1F.2050502@huawei.com
      
      Reported-by: default avatarFengguang Wu <fengguang.wu@intel.com>
      Signed-off-by: default avatarLi Zefan <lizefan@huawei.com>
      Signed-off-by: default avatarSteven Rostedt <rostedt@goodmis.org>
      523c8113
    • Steven Rostedt (Red Hat)'s avatar
      tracing: Fix trace events build without modules · 315326c1
      Steven Rostedt (Red Hat) authored
      
      
      The new multi-buffers added a descriptor that kept track of module
      events, and the directories they use, with struct ftace_module_file_ops.
      This is used to add a ref count to keep modules from unloading while
      their files are being accessed.
      
      As the descriptor is only needed when CONFIG_MODULES is enabled, it
      is only declared when the config is enabled. But that struct is
      dereferenced in a few areas outside the #ifdef CONFIG_MODULES.
      
      By adding some helper routines and moving code around a little,
      events can be compiled again without modules.
      Reported-by: default avatarFengguang Wu <fengguang.wu@intel.com>
      Signed-off-by: default avatarSteven Rostedt <rostedt@goodmis.org>
      315326c1
    • Steven Rostedt (Red Hat)'s avatar
      tracing: Add __per_cpu annotation to trace array percpu data pointer · 34ef61b1
      Steven Rostedt (Red Hat) authored
      
      
      With the conversion of the data array to per cpu, sparse now complains
      about the use of per_cpu_ptr() on the variable. But The variable is
      allocated with alloc_percpu() and is fine to use. But since the structure
      that contains the data variable does not annotate it as such, sparse
      gives out a lot of false warnings.
      Reported-by: default avatarFengguang Wu <fengguang.wu@intel.com>
      Signed-off-by: default avatarSteven Rostedt <rostedt@goodmis.org>
      34ef61b1
    • Li Zefan's avatar
      tracing/syscalls: Annotate field-defining functions with __init · b8aae39f
      Li Zefan authored
      These two functions are called during kernel boot only.
      
      Link: http://lkml.kernel.org/r/51258796.7020704@huawei.com
      
      Signed-off-by: default avatarLi Zefan <lizefan@huawei.com>
      Signed-off-by: default avatarSteven Rostedt <rostedt@goodmis.org>
      b8aae39f
    • Li Zefan's avatar
      tracing: Annotate event field-defining functions with __init · 7e4f44b1
      Li Zefan authored
      Those functions are called either during kernel boot or module init.
      
      Before:
      
      $ dmesg | grep 'Freeing unused kernel memory'
      Freeing unused kernel memory: 1208k freed
      Freeing unused kernel memory: 1360k freed
      Freeing unused kernel memory: 1960k freed
      
      After:
      
      $ dmesg | grep 'Freeing unused kernel memory'
      Freeing unused kernel memory: 1236k freed
      Freeing unused kernel memory: 1388k freed
      Freeing unused kernel memory: 1960k freed
      
      Link: http://lkml.kernel.org/r/5125877D.5000201@huawei.com
      
      Signed-off-by: default avatarLi Zefan <lizefan@huawei.com>
      Signed-off-by: default avatarSteven Rostedt <rostedt@goodmis.org>
      7e4f44b1
    • Li Zefan's avatar
      tracing: Add a helper function for event print functions · f71130de
      Li Zefan authored
      Move duplicate code in event print functions to a helper function.
      
      This shrinks the size of the kernel by ~13K.
      
         text    data     bss     dec     hex filename
      6596137 1743966 10138672        18478775        119f6b7 vmlinux.o.old
      6583002 1743849 10138672        18465523        119c2f3 vmlinux.o.new
      
      Link: http://lkml.kernel.org/r/51258746.2060304@huawei.com
      
      Signed-off-by: default avatarLi Zefan <lizefan@huawei.com>
      Signed-off-by: default avatarSteven Rostedt <rostedt@goodmis.org>
      f71130de
    • Steven Rostedt (Red Hat)'s avatar
      tracing/ring-buffer: Move poll wake ups into ring buffer code · 15693458
      Steven Rostedt (Red Hat) authored
      
      
      Move the logic to wake up on ring buffer data into the ring buffer
      code itself. This simplifies the tracing code a lot and also has the
      added benefit that waiters on one of the instance buffers can be woken
      only when data is added to that instance instead of data added to
      any instance.
      Signed-off-by: default avatarSteven Rostedt <rostedt@goodmis.org>
      15693458
    • Steven Rostedt's avatar
      tracing: Fix read blocking on trace_pipe_raw · b627344f
      Steven Rostedt authored
      
      
      If the ring buffer is empty, a read to trace_pipe_raw wont block.
      The tracing code has the infrastructure to wake up waiting readers,
      but the trace_pipe_raw doesn't take advantage of that.
      
      When a read is done to trace_pipe_raw without the O_NONBLOCK flag
      set, have the read block until there's data in the requested buffer.
      Signed-off-by: default avatarSteven Rostedt <rostedt@goodmis.org>
      b627344f
    • Steven Rostedt's avatar
      tracing: Fix polling on trace_pipe_raw · cc60cdc9
      Steven Rostedt authored
      
      
      The trace_pipe_raw never implemented polling and this was casing
      issues for several utilities. This is now implemented.
      
      Blocked reads still are on the TODO list.
      Reported-by: default avatarMauro Carvalho Chehab <mchehab@redhat.com>
      Tested-by: default avatarMauro Carvalho Chehab <mchehab@redhat.com>
      Signed-off-by: default avatarSteven Rostedt <rostedt@goodmis.org>
      cc60cdc9
    • Steven Rostedt (Red Hat)'s avatar
      tracing: Do not block on splice if either file or splice NONBLOCK flag is set · 189e5784
      Steven Rostedt (Red Hat) authored
      
      
      Currently only the splice NONBLOCK flag is checked to determine if
      the splice read should block or not. But the file descriptor NONBLOCK
      flag also needs to be checked.
      Signed-off-by: default avatarSteven Rostedt <rostedt@goodmis.org>
      189e5784
    • Steven Rostedt's avatar
      tracing: Use direct field, type and system names · 92edca07
      Steven Rostedt authored
      
      
      The names used to display the field and type in the event format
      files are copied, as well as the system name that is displayed.
      
      All these names are created by constant values passed in.
      If one of theses values were to be removed by a module, the module
      would also be required to remove any event it created.
      
      By using the strings directly, we can save over 100K of memory.
      Signed-off-by: default avatarSteven Rostedt <rostedt@goodmis.org>
      92edca07
    • Steven Rostedt's avatar
      tracing: Use kmem_cache_alloc instead of kmalloc in trace_events.c · d1a29143
      Steven Rostedt authored
      
      
      The event structures used by the trace events are mostly persistent,
      but they are also allocated by kmalloc, which is not the best at
      allocating space for what is used. By converting these kmallocs
      into kmem_cache_allocs, we can save over 50K of space that is
      permanently allocated.
      
      After boot we have:
      
       slab name          active allocated size
       ---------          ------ --------- ----
      ftrace_event_file    979   1005     56   67    1
      ftrace_event_field   2301   2310     48   77    1
      
      The ftrace_event_file has at boot up 979 active objects out of
      1005 allocated in the slabs. Each object is 56 bytes. In a normal
      kmalloc, that would allocate 64 bytes for each object.
      
       1005 - 979  = 26 objects not used
       26 * 56 = 1456 bytes wasted
      
      But if we used kmalloc:
      
       64 - 56 = 8 bytes unused per allocation
       8 * 979 = 7832 bytes wasted
      
       7832 - 1456 = 6376 bytes in savings
      
      Doing the same for ftrace_event_field where there's 2301 objects
      allocated in a slab that can hold 2310 with 48 bytes each we have:
      
       2310 - 2301 = 9 objects not used
       9 * 48 = 432 bytes wasted
      
      A kmalloc would also use 64 bytes per object:
      
       64 - 48 = 16 bytes unused per allocation
       16 * 2301 = 36816 bytes wasted!
      
       36816 - 432 = 36384 bytes in savings
      
      This change gives us a total of 42760 bytes in savings. At least
      on my machine, but as there's a lot of these persistent objects
      for all configurations that use trace points, this is a net win.
      
      Thanks to Ezequiel Garcia for his trace_analyze presentation which
      pointed out the wasted space in my code.
      
      Cc: Ezequiel Garcia <elezegarcia@gmail.com>
      Signed-off-by: default avatarSteven Rostedt <rostedt@goodmis.org>
      d1a29143
    • Steven Rostedt's avatar
      tracing: Get trace_events kernel command line working again · 77248221
      Steven Rostedt authored
      
      
      With the new descriptors used to allow multiple buffers in the
      tracing directory added, the kernel command line parameter
      trace_events=... no longer works. This is because the top level
      (global) trace array now has a list of descriptors associated
      with the events and the files in the debugfs directory. But in
      early bootup, when the command line is processed and the events
      enabled, the trace array list of events has not been set up yet.
      
      Without the list of events in the trace array, the setting of
      events to record will fail because it would not match any events.
      
      The solution is to set up the top level array in two stages.
      The first is to just add the ftrace file descriptors that just point
      to the events. This will allow events to be enabled and start tracing.
      The second stage is called after the filesystem is set up, and this
      stage will create the debugfs event files and directories associated
      with the trace array events.
      Signed-off-by: default avatarSteven Rostedt <rostedt@goodmis.org>
      77248221
    • Steven Rostedt's avatar
      tracing: Add rmdir to remove multibuffer instances · 0c8916c3
      Steven Rostedt authored
      
      
      Add a method to the hijacked dentry descriptor of the
      "instances" directory to allow for rmdir to remove an
      instance of a multibuffer.
      
      Example:
      
        cd /debug/tracing/instances
        mkdir hello
        ls
      hello/
        rmdir hello
        ls
      
      Like the mkdir method, the i_mutex is dropped for the instances
      directory. The instances directory is created at boot up and can
      not be renamed or removed. The trace_types_lock mutex is used to
      synchronize adding and removing of instances.
      
      I've run several stress tests with different threads trying to
      create and delete directories of the same name, and it has stood
      up fine.
      
      Cc: Al Viro <viro@zeniv.linux.org.uk>
      Signed-off-by: default avatarSteven Rostedt <rostedt@goodmis.org>
      0c8916c3
    • Steven Rostedt's avatar
      tracing: Add interface to allow multiple trace buffers · 277ba044
      Steven Rostedt authored
      
      
      Add the interface ("instances" directory) to add multiple buffers
      to ftrace. To create a new instance, simply do a mkdir in the
      instances directory:
      
      This will create a directory with the following:
      
       # cd instances
       # mkdir foo
       # ls foo
      buffer_size_kb        free_buffer  trace_clock    trace_pipe
      buffer_total_size_kb  set_event    trace_marker   tracing_enabled
      events/               trace        trace_options  tracing_on
      
      Currently only events are able to be set, and there isn't a way
      to delete a buffer when one is created (yet).
      
      Note, the i_mutex lock is dropped from the parent "instances"
      directory during the mkdir operation. As the "instances" directory
      can not be renamed or deleted (created on boot), I do not see
      any harm in dropping the lock. The creation of the sub directories
      is protected by trace_types_lock mutex, which only lets one
      instance get into the code path at a time. If two tasks try to
      create or delete directories of the same name, only one will occur
      and the other will fail with -EEXIST.
      
      Cc: Al Viro <viro@zeniv.linux.org.uk>
      Signed-off-by: default avatarSteven Rostedt <rostedt@goodmis.org>
      277ba044
    • Steven Rostedt's avatar
      tracing: Make syscall events suitable for multiple buffers · 12ab74ee
      Steven Rostedt authored
      
      
      Currently the syscall events record into the global buffer. But if
      multiple buffers are in place, then we need to have syscall events
      record in the proper buffers.
      
      By adding descriptors to pass to the syscall event functions, the
      syscall events can now record into the buffers that have been assigned
      to them (one event may be applied to mulitple buffers).
      
      This will allow tracing high volume syscalls along with seldom occurring
      syscalls without losing the seldom syscall events.
      Signed-off-by: default avatarSteven Rostedt <rostedt@goodmis.org>
      12ab74ee
    • Steven Rostedt's avatar
      tracing: Replace the static global per_cpu arrays with allocated per_cpu · a7603ff4
      Steven Rostedt authored
      
      
      The global and max-tr currently use static per_cpu arrays for the CPU data
      descriptors. But in order to get new allocated trace_arrays, they need to
      be allocated per_cpu arrays. Instead of using the static arrays, switch
      the global and max-tr to use allocated data.
      Signed-off-by: default avatarSteven Rostedt <rostedt@goodmis.org>
      a7603ff4
    • Steven Rostedt's avatar
      tracing: Pass the ftrace_file to the buffer lock reserve code · ccb469a1
      Steven Rostedt authored
      
      
      Pass the struct ftrace_event_file *ftrace_file to the
      trace_event_buffer_lock_reserve() (new function that replaces the
      trace_current_buffer_lock_reserver()).
      
      The ftrace_file holds a pointer to the trace_array that is in use.
      In the case of multiple buffers with different trace_arrays, this
      allows different events to be recorded into different buffers.
      
      Also fixed some of the stale comments in include/trace/ftrace.h
      Signed-off-by: default avatarSteven Rostedt <rostedt@goodmis.org>
      ccb469a1
    • Steven Rostedt's avatar
      tracing: Encapsulate global_trace and remove dependencies on global vars · 2b6080f2
      Steven Rostedt authored
      
      
      The global_trace variable in kernel/trace/trace.c has been kept 'static' and
      local to that file so that it would not be used too much outside of that
      file. This has paid off, even though there were lots of changes to make
      the trace_array structure more generic (not depending on global_trace).
      
      Removal of a lot of direct usages of global_trace is needed to be able to
      create more trace_arrays such that we can add multiple buffers.
      Signed-off-by: default avatarSteven Rostedt <rostedt@goodmis.org>
      2b6080f2
    • Steven Rostedt's avatar
      tracing: Use RING_BUFFER_ALL_CPUS for TRACE_PIPE_ALL_CPU · ae3b5093
      Steven Rostedt authored
      
      
      Both RING_BUFFER_ALL_CPUS and TRACE_PIPE_ALL_CPU are defined as
      -1 and used to say that all the ring buffers are to be modified
      or read (instead of just a single cpu, which would be >= 0).
      
      There's no reason to keep TRACE_PIPE_ALL_CPU as it is also started
      to be used for more than what it was created for, and now that
      the ring buffer code added a generic RING_BUFFER_ALL_CPUS define,
      we can clean up the trace code to use that instead and remove
      the TRACE_PIPE_ALL_CPU macro.
      Signed-off-by: default avatarSteven Rostedt <rostedt@goodmis.org>
      ae3b5093
    • Steven Rostedt's avatar
      tracing: Separate out trace events from global variables · ae63b31e
      Steven Rostedt authored
      
      
      The trace events for ftrace are all defined via global variables.
      The arrays of events and event systems are linked to a global list.
      This prevents multiple users of the event system (what to enable and
      what not to).
      
      By adding descriptors to represent the event/file relation, as well
      as to which trace_array descriptor they are associated with, allows
      for more than one set of events to be defined. Once the trace events
      files have a link between the trace event and the trace_array they
      are associated with, we can create multiple trace_arrays that can
      record separate events in separate buffers.
      Signed-off-by: default avatarSteven Rostedt <rostedt@goodmis.org>
      ae63b31e
    • Steven Rostedt (Red Hat)'s avatar
      tracing: Prevent buffer overwrite disabled for latency tracers · 613f04a0
      Steven Rostedt (Red Hat) authored
      
      
      The latency tracers require the buffers to be in overwrite mode,
      otherwise they get screwed up. Force the buffers to stay in overwrite
      mode when latency tracers are enabled.
      
      Added a flag_changed() method to the tracer structure to allow
      the tracers to see what flags are being changed, and also be able
      to prevent the change from happing.
      
      Cc: stable@vger.kernel.org
      Signed-off-by: default avatarSteven Rostedt <rostedt@goodmis.org>
      613f04a0
    • Steven Rostedt (Red Hat)'s avatar
      tracing: Keep overwrite in sync between regular and snapshot buffers · 80902822
      Steven Rostedt (Red Hat) authored
      
      
      Changing the overwrite mode for the ring buffer via the trace
      option only sets the normal buffer. But the snapshot buffer could
      swap with it, and then the snapshot would be in non overwrite mode
      and the normal buffer would be in overwrite mode, even though the
      option flag states otherwise.
      
      Keep the two buffers overwrite modes in sync.
      
      Cc: stable@vger.kernel.org
      Signed-off-by: default avatarSteven Rostedt <rostedt@goodmis.org>
      80902822
  2. 14 Mar, 2013 1 commit
  3. 13 Mar, 2013 1 commit
    • Steven Rostedt (Red Hat)'s avatar
      tracing: Fix free of probe entry by calling call_rcu_sched() · 740466bc
      Steven Rostedt (Red Hat) authored
      
      
      Because function tracing is very invasive, and can even trace
      calls to rcu_read_lock(), RCU access in function tracing is done
      with preempt_disable_notrace(). This requires a synchronize_sched()
      for updates and not a synchronize_rcu().
      
      Function probes (traceon, traceoff, etc) must be freed after
      a synchronize_sched() after its entry has been removed from the
      hash. But call_rcu() is used. Fix this by using call_rcu_sched().
      
      Also fix the usage to use hlist_del_rcu() instead of hlist_del().
      
      Cc: stable@vger.kernel.org
      Cc: Paul McKenney <paulmck@linux.vnet.ibm.com>
      Signed-off-by: default avatarSteven Rostedt <rostedt@goodmis.org>
      740466bc
  4. 12 Mar, 2013 1 commit
    • Steven Rostedt (Red Hat)'s avatar
      tracing: Fix race in snapshot swapping · 2721e72d
      Steven Rostedt (Red Hat) authored
      
      
      Although the swap is wrapped with a spin_lock, the assignment
      of the temp buffer used to swap is not within that lock.
      It needs to be moved into that lock, otherwise two swaps
      happening on two different CPUs, can end up using the wrong
      temp buffer to assign in the swap.
      
      Luckily, all current callers of the swap function appear to have
      their own locks. But in case something is added that allows two
      different callers to call the swap, then there's a chance that
      this race can trigger and corrupt the buffers.
      
      New code is coming soon that will allow for this race to trigger.
      
      I've Cc'd stable, so this bug will not show up if someone backports
      one of the changes that can trigger this bug.
      
      Cc: stable@vger.kernel.org
      Signed-off-by: default avatarSteven Rostedt <rostedt@goodmis.org>
      2721e72d