1. 01 May, 2017 1 commit
    • Steven Rostedt (VMware)'s avatar
      ring-buffer: Return reader page back into existing ring buffer · 73a757e6
      Steven Rostedt (VMware) authored
      When reading the ring buffer for consuming, it is optimized for splice,
      where a page is taken out of the ring buffer (zero copy) and sent to the
      reading consumer. When the read is finished with the page, it calls
      ring_buffer_free_read_page(), which simply frees the page. The next time the
      reader needs to get a page from the ring buffer, it must call
      ring_buffer_alloc_read_page() which allocates and initializes a reader page
      for the ring buffer to be swapped into the ring buffer for a new filled page
      for the reader.
      
      The problem is that there's no reason to actually free the page when it is
      passed back to the ring buffer. It can hold it off and reuse it for the next
      iteration. This completely removes the interaction with the page_alloc
      mechanism.
      
      Using the trace-cmd utility to record all events (causing trace-cmd to
      require reading lots of pages from the ring buffer, and calling
      ring_buffer_alloc/free_read_page() several times), and also assigning a
      stack trace trigger to the mm_page_alloc event, we can see how many times
      the ring_buffer_alloc_read_page() needed to allocate a page for the ring
      buffer.
      
      Before this change:
      
        # trace-cmd record -e all -e mem_page_alloc -R stacktrace sleep 1
        # trace-cmd report |grep ring_buffer_alloc_read_page | wc -l
        9968
      
      After this change:
      
        # trace-cmd record -e all -e mem_page_alloc -R stacktrace sleep 1
        # trace-cmd report |grep ring_buffer_alloc_read_page | wc -l
        4
      Signed-off-by: default avatarSteven Rostedt (VMware) <rostedt@goodmis.org>
      73a757e6
  2. 26 Apr, 2017 5 commits
  3. 21 Apr, 2017 23 commits
  4. 18 Apr, 2017 5 commits
    • Steven Rostedt (VMware)'s avatar
      ftrace: Move the probe function into the tracing directory · ec19b859
      Steven Rostedt (VMware) authored
      As nothing outside the tracing directory uses the function probes mechanism,
      I'm moving the prototypes out of the include/linux/ftrace.h and into the
      local kernel/trace/trace.h header. I plan on making them hook to the
      trace_array structure which is local to kernel/trace, and I do not want to
      expose it to the rest of the kernel. This requires that the probe functions
      must also be local to tracing. But luckily nothing else uses them.
      Signed-off-by: default avatarSteven Rostedt (VMware) <rostedt@goodmis.org>
      ec19b859
    • Steven Rostedt (VMware)'s avatar
      selftests: ftrace: Add test to test reading of set_ftrace_file · a9064f67
      Steven Rostedt (VMware) authored
      The set_ftrace_file lists both functions that are filtered, as well as
      function probes (triggers) that are attached to a function, like traceon or
      stacktrace, etc. The reading of this file is not as trivial as most pseudo
      files are, and there's been various bugs that have appeared in the past
      when there's a mix of probes and functions listed. There's also a difference
      when reading the file using dd with a block size of 1.
      
      This test performs the following:
      
       o Resets set_ftrace_filter
      
       o Makes sure only "#### all functions enabled ####" is listed
      
          (All checks uses cat, and dd with bs=1 and bs=100)
      
       o Adds a traceon trigger to schedule
      
       o Checks if only "#### all function enabled ####" and the trigger is there.
      
       o Adds tracing of schedule
      
       o Checks if only schedule and the trigger is there
      
       o Adds tracing of do_IRQ as well
      
       o Checks if only schedule, do_IRQ and the trigger is there
      
       o Adds a traceon trigger to do_IRQ
      
       o Checks if only schedule, do_IRQ and both triggers are there
      
       o Removes tracing of do_IRQ
      
       o Checks if only schedule and both triggers are there
      
       o Removes tracing of schedule
      
       o Checks if only  "#### all functions enabled ####" and both triggers are there
      
       o Removes the triggers
      
       o Checks if only "#### all functions enabled ####" is there
      
       o Adds tracing of schedule
      
       o Checks if only schedule is there
      
       o Adds tracing of do_IRQ
      
       o Checks if only schedule and do_IRQ are there
      Signed-off-by: default avatarSteven Rostedt (VMware) <rostedt@goodmis.org>
      a9064f67
    • Steven Rostedt (VMware)'s avatar
      selftests: ftrace: Add a test to test function triggers to start and stop tracing · d8b39e1d
      Steven Rostedt (VMware) authored
      This adds a test to test the function tiggers traceon and traceoff to make
      sure that it starts and stops tracing when a function is hit.
      
      The test performs the following:
      
       o Enables all events
      
       o Writes schedule:traceoff into set_ftrace_filter
      
       o Makes sure the tigger exists in the file
      
       o Makes sure the trace file no longer grows
      
       o Makes sure that tracing_on is now zero
      
       o Clears the trace file
      
       o Makes sure it's still empty
      
       o Removes the trigger
      
       o Makes sure tracing is still off (tracing_on is zero)
      
       o Writes schedule:traceon into set_ftrace_filter
      
       o Makes sure the trace file is no longer empty
      
       o Makes sure that tracing_on file is set to one
      
       o Removes the trigger
      
       o Makes sure the trigger is no longer there
      
       o Writes schedule:traceoff:3 into set_ftrace_filter
      
       o Makes sure that tracing_on turns off
      
         . Writes 1 into tracing_on
      
         . Makes sure that it turns off 2 more times
      
       o Writes 1 into tracing_on
      
       o Makes sure that tracing_on is still a one
      Signed-off-by: default avatarSteven Rostedt (VMware) <rostedt@goodmis.org>
      d8b39e1d
    • Steven Rostedt (VMware)'s avatar
      selftests: ftrace: Add a selftest to test event enable/disable func trigger · 43bb45da
      Steven Rostedt (VMware) authored
      This adds a test to enable and disable trace events via the function
      triggers. It tests enabling and disabling the sched:sched_switch event via
      the the event_enable and event_disable function triggers attached to the
      schedule() kernel function.
      
      The test does the following:
      
       o disable all events
      
       o disables or enables the sched_switch event
      
       o writes schedule:event_enable/disable:sched:sched_switch into set_ftrace_filter
      
       o 5 times it checks to make sure:
      
          . Writes 0/1 into the sched_switch/enable
      
          . Checks that the sched_switch/enable goes back to 1/0
      
       o Resets the events
      
       o writes schedule:event_enable/disable:sched:sched_switch:3 into set_ftrace_filter
      
       o Does a loop of 3 to see that sched_switch/enable file gets updated
      
       o Makes sure the sched_switch/enable stops getting updated
      Signed-off-by: default avatarSteven Rostedt (VMware) <rostedt@goodmis.org>
      43bb45da
    • Steven Rostedt (VMware)'s avatar
      selftests: ftrace: Add a way to reset triggers in the set_ftrace_filter file · 8e5e19c1
      Steven Rostedt (VMware) authored
      Just writing into the set_ftrace_filter file does not reset triggers, even
      though it can reset the function list. Triggers require writing the trigger
      name with a "!" prepended. It's worse that it requires the number if the
      trigger has a count associated to it.
      
      Add a reset_ftrace_filter function to the ftrace self tests to allow for the
      tests to have a generic way to clear them. It also resets any functions that
      are listed in that file as well.
      Signed-off-by: default avatarSteven Rostedt (VMware) <rostedt@goodmis.org>
      8e5e19c1
  5. 17 Apr, 2017 4 commits
  6. 15 Apr, 2017 1 commit
    • Steven Rostedt (VMware)'s avatar
      ftrace: Fix removing of second function probe · acceb72e
      Steven Rostedt (VMware) authored
      When two function probes are added to set_ftrace_filter, and then one of
      them is removed, the update to the function locations is not performed, and
      the record keeping of the function states are corrupted, and causes an
      ftrace_bug() to occur.
      
      This is easily reproducable by adding two probes, removing one, and then
      adding it back again.
      
       # cd /sys/kernel/debug/tracing
       # echo schedule:traceoff > set_ftrace_filter
       # echo do_IRQ:traceoff > set_ftrace_filter
       # echo \!do_IRQ:traceoff > /debug/tracing/set_ftrace_filter
       # echo do_IRQ:traceoff > set_ftrace_filter
      
      Causes:
       ------------[ cut here ]------------
       WARNING: CPU: 2 PID: 1098 at kernel/trace/ftrace.c:2369 ftrace_get_addr_curr+0x143/0x220
       Modules linked in: [...]
       CPU: 2 PID: 1098 Comm: bash Not tainted 4.10.0-test+ #405
       Hardware name: Hewlett-Packard HP Compaq Pro 6300 SFF/339A, BIOS K01 v02.05 05/07/2012
       Call Trace:
        dump_stack+0x68/0x9f
        __warn+0x111/0x130
        ? trace_irq_work_interrupt+0xa0/0xa0
        warn_slowpath_null+0x1d/0x20
        ftrace_get_addr_curr+0x143/0x220
        ? __fentry__+0x10/0x10
        ftrace_replace_code+0xe3/0x4f0
        ? ftrace_int3_handler+0x90/0x90
        ? printk+0x99/0xb5
        ? 0xffffffff81000000
        ftrace_modify_all_code+0x97/0x110
        arch_ftrace_update_code+0x10/0x20
        ftrace_run_update_code+0x1c/0x60
        ftrace_run_modify_code.isra.48.constprop.62+0x8e/0xd0
        register_ftrace_function_probe+0x4b6/0x590
        ? ftrace_startup+0x310/0x310
        ? debug_lockdep_rcu_enabled.part.4+0x1a/0x30
        ? update_stack_state+0x88/0x110
        ? ftrace_regex_write.isra.43.part.44+0x1d3/0x320
        ? preempt_count_sub+0x18/0xd0
        ? mutex_lock_nested+0x104/0x800
        ? ftrace_regex_write.isra.43.part.44+0x1d3/0x320
        ? __unwind_start+0x1c0/0x1c0
        ? _mutex_lock_nest_lock+0x800/0x800
        ftrace_trace_probe_callback.isra.3+0xc0/0x130
        ? func_set_flag+0xe0/0xe0
        ? __lock_acquire+0x642/0x1790
        ? __might_fault+0x1e/0x20
        ? trace_get_user+0x398/0x470
        ? strcmp+0x35/0x60
        ftrace_trace_onoff_callback+0x48/0x70
        ftrace_regex_write.isra.43.part.44+0x251/0x320
        ? match_records+0x420/0x420
        ftrace_filter_write+0x2b/0x30
        __vfs_write+0xd7/0x330
        ? do_loop_readv_writev+0x120/0x120
        ? locks_remove_posix+0x90/0x2f0
        ? do_lock_file_wait+0x160/0x160
        ? __lock_is_held+0x93/0x100
        ? rcu_read_lock_sched_held+0x5c/0xb0
        ? preempt_count_sub+0x18/0xd0
        ? __sb_start_write+0x10a/0x230
        ? vfs_write+0x222/0x240
        vfs_write+0xef/0x240
        SyS_write+0xab/0x130
        ? SyS_read+0x130/0x130
        ? trace_hardirqs_on_caller+0x182/0x280
        ? trace_hardirqs_on_thunk+0x1a/0x1c
        entry_SYSCALL_64_fastpath+0x18/0xad
       RIP: 0033:0x7fe61c157c30
       RSP: 002b:00007ffe87890258 EFLAGS: 00000246 ORIG_RAX: 0000000000000001
       RAX: ffffffffffffffda RBX: ffffffff8114a410 RCX: 00007fe61c157c30
       RDX: 0000000000000010 RSI: 000055814798f5e0 RDI: 0000000000000001
       RBP: ffff8800c9027f98 R08: 00007fe61c422740 R09: 00007fe61ca53700
       R10: 0000000000000073 R11: 0000000000000246 R12: 0000558147a36400
       R13: 00007ffe8788f160 R14: 0000000000000024 R15: 00007ffe8788f15c
        ? trace_hardirqs_off_caller+0xc0/0x110
       ---[ end trace 99fa09b3d9869c2c ]---
       Bad trampoline accounting at: ffffffff81cc3b00 (do_IRQ+0x0/0x150)
      
      Cc: stable@vger.kernel.org
      Fixes: 59df055f ("ftrace: trace different functions with a different tracer")
      Signed-off-by: default avatarSteven Rostedt (VMware) <rostedt@goodmis.org>
      acceb72e
  7. 10 Apr, 2017 1 commit