1. 16 May, 2019 1 commit
    • Steven Rostedt (VMware)'s avatar
      tracing/fgraph: Fix set_graph_function from showing interrupts · 02cf6220
      Steven Rostedt (VMware) authored
      [ Upstream commit 5cf99a0f3161bc3ae2391269d134d6bf7e26f00e ]
      
      The tracefs file set_graph_function is used to only function graph functions
      that are listed in that file (or all functions if the file is empty). The
      way this is implemented is that the function graph tracer looks at every
      function, and if the current depth is zero and the function matches
      something in the file then it will trace that function. When other functions
      are called, the depth will be greater than zero (because the original
      function will be at depth zero), and all functions will be traced where the
      depth is greater than zero.
      
      The issue is that when a function is first entered, and the handler that
      checks this logic is called, the depth is set to zero. If an interrupt comes
      in and a function in the interrupt handler is traced, its depth will be
      greater than zero and it will automatically be traced, even if the original
      function was not. But because the logic only looks at depth it may trace
      interrupts when it should not be.
      
      The recent design change of the function graph tracer to fix other bugs
      caused the depth to be zero while the function graph callback handler is
      being called for a longer time, widening the race of this happening. This
      bug was actually there for a longer time, but because the race window was so
      small it seldom happened. The Fixes tag below is for the commit that widen
      the race window, because that commit belongs to a series that will also help
      fix the original bug.
      
      Cc: stable@kernel.org
      Fixes: 39eb456dacb5 ("function_graph: Use new curr_ret_depth to manage depth instead of curr_ret_stack")
      Reported-by: default avatarJoe Lawrence <joe.lawrence@redhat.com>
      Tested-by: default avatarJoe Lawrence <joe.lawrence@redhat.com>
      Signed-off-by: default avatarSteven Rostedt (VMware) <rostedt@goodmis.org>
      Signed-off-by: default avatarSasha Levin <alexander.levin@microsoft.com>
      02cf6220
  2. 23 Sep, 2018 1 commit
    • Philippe Gerum's avatar
      ftrace: ipipe: enable tracing from the head domain · e10253e0
      Philippe Gerum authored
      Enabling ftrace for a co-kernel running in the head domain of a
      pipelined interrupt context means to:
      
      - make sure that ftrace's live kernel code patching still runs
        unpreempted by any head domain activity (so that the latter can't
        tread on invalid or half-baked changes in the .text section).
      
      - allow the co-kernel code running in the head domain to traverse
        ftrace's tracepoints safely.
      
      The changes introduced by this commit ensure this by fixing up some
      key critical sections so that interrupts are still disabled in the
      CPU, undoing the interrupt flag virtualization in those particular
      cases.
      e10253e0
  3. 11 Jul, 2018 1 commit
    • Changbin Du's avatar
      tracing: Fix missing return symbol in function_graph output · 54f1da1f
      Changbin Du authored
      commit 1fe4293f upstream.
      
      The function_graph tracer does not show the interrupt return marker for the
      leaf entry. On leaf entries, we see an unbalanced interrupt marker (the
      interrupt was entered, but nevern left).
      
      Before:
       1)               |  SyS_write() {
       1)               |    __fdget_pos() {
       1)   0.061 us    |      __fget_light();
       1)   0.289 us    |    }
       1)               |    vfs_write() {
       1)   0.049 us    |      rw_verify_area();
       1) + 15.424 us   |      __vfs_write();
       1)   ==========> |
       1)   6.003 us    |      smp_apic_timer_interrupt();
       1)   0.055 us    |      __fsnotify_parent();
       1)   0.073 us    |      fsnotify();
       1) + 23.665 us   |    }
       1) + 24.501 us   |  }
      
      After:
       0)               |  SyS_write() {
       0)               |    __fdget_pos() {
       0)   0.052 us    |      __fget_light();
       0)   0.328 us    |    }
       0)               |    vfs_write() {
       0)   0.057 us    |      rw_verify_area();
       0)               |      __vfs_write() {
       0)   ==========> |
       0)   8.548 us    |      smp_apic_timer_interrupt();
       0)   <========== |
       0) + 36.507 us   |      } /* __vfs_write */
       0)   0.049 us    |      __fsnotify_parent();
       0)   0.066 us    |      fsnotify();
       0) + 50.064 us   |    }
       0) + 50.952 us   |  }
      
      Link: http://lkml.kernel.org/r/1517413729-20411-1-git-send-email-changbin.du@intel.com
      
      Cc: stable@vger.kernel.org
      Fixes: f8b755ac ("tracing/function-graph-tracer: Output arrows signal on hardirq call/return")
      Signed-off-by: default avatarChangbin Du <changbin.du@intel.com>
      Signed-off-by: default avatarSteven Rostedt (VMware) <rostedt@goodmis.org>
      Signed-off-by: default avatarGreg Kroah-Hartman <gregkh@linuxfoundation.org>
      54f1da1f
  4. 02 Nov, 2017 1 commit
    • Greg Kroah-Hartman's avatar
      License cleanup: add SPDX GPL-2.0 license identifier to files with no license · b2441318
      Greg Kroah-Hartman authored
      Many source files in the tree are missing licensing information, which
      makes it harder for compliance tools to determine the correct license.
      
      By default all files without license information are under the default
      license of the kernel, which is GPL version 2.
      
      Update the files which contain no license information with the 'GPL-2.0'
      SPDX license identifier.  The SPDX identifier is a legally binding
      shorthand, which can be used instead of the full boiler plate text.
      
      This patch is based on work done by Thomas Gleixner and Kate Stewart and
      Philippe Ombredanne.
      
      How this work was done:
      
      Patches were generated and checked against linux-4.14-rc6 for a subset of
      the use cases:
       - file had no licensing information it it.
       - file was a */uapi/* one with no licensing information in it,
       - file was a */uapi/* one with existing licensing information,
      
      Further patches will be generated in subsequent months to fix up cases
      where non-standard license headers were used, and references to license
      had to be inferred by heuristics based on keywords.
      
      The analysis to determine which SPDX License Identifier to be applied to
      a file was done in a spreadsheet of side by side results from of the
      output of two independent scanners (ScanCode & Windriver) producing SPDX
      tag:value files created by Philippe Ombredanne.  Philippe prepared the
      base worksheet, and did an initial spot review of a few 1000 files.
      
      The 4.13 kernel was the starting point of the analysis with 60,537 files
      assessed.  Kate Stewart did a file by file comparison of the scanner
      results in the spreadsheet to determine which SPDX license identifier(s)
      to be applied to the file. She confirmed any determination that was not
      immediately clear with lawyers working with the Linux Foundation.
      
      Criteria used to select files for SPDX license identifier tagging was:
       - Files considered eligible had to be source code files.
       - Make and config files were included as candidates if they contained >5
         lines of source
       - File already had some variant of a license header in it (even if <5
         lines).
      
      All documentation files were explicitly excluded.
      
      The following heuristics were used to determine which SPDX license
      identifiers to apply.
      
       - when both scanners couldn't find any license traces, file was
         considered to have no license information in it, and the top level
         COPYING file license applied.
      
         For non */uapi/* files that summary was:
      
         SPDX license identifier                            # files
         ---------------------------------------------------|-------
         GPL-2.0                                              11139
      
         and resulted in the first patch in this series.
      
         If that file was a */uapi/* path one, it was "GPL-2.0 WITH
         Linux-syscall-note" otherwise it was "GPL-2.0".  Results of that was:
      
         SPDX license identifier                            # files
         ---------------------------------------------------|-------
         GPL-2.0 WITH Linux-syscall-note                        930
      
         and resulted in the second patch in this series.
      
       - if a file had some form of licensing information in it, and was one
         of the */uapi/* ones, it was denoted with the Linux-syscall-note if
         any GPL family license was found in the file or had no licensing in
         it (per prior point).  Results summary:
      
         SPDX license identifier                            # files
         ---------------------------------------------------|------
         GPL-2.0 WITH Linux-syscall-note                       270
         GPL-2.0+ WITH Linux-syscall-note                      169
         ((GPL-2.0 WITH Linux-syscall-note) OR BSD-2-Clause)    21
         ((GPL-2.0 WITH Linux-syscall-note) OR BSD-3-Clause)    17
         LGPL-2.1+ WITH Linux-syscall-note                      15
         GPL-1.0+ WITH Linux-syscall-note                       14
         ((GPL-2.0+ WITH Linux-syscall-note) OR BSD-3-Clause)    5
         LGPL-2.0+ WITH Linux-syscall-note                       4
         LGPL-2.1 WITH Linux-syscall-note                        3
         ((GPL-2.0 WITH Linux-syscall-note) OR MIT)              3
         ((GPL-2.0 WITH Linux-syscall-note) AND MIT)             1
      
         and that resulted in the third patch in this series.
      
       - when the two scanners agreed on the detected license(s), that became
         the concluded license(s).
      
       - when there was disagreement between the two scanners (one detected a
         license but the other didn't, or they both detected different
         licenses) a manual inspection of the file occurred.
      
       - In most cases a manual inspection of the information in the file
         resulted in a clear resolution of the license that should apply (and
         which scanner probably needed to revisit its heuristics).
      
       - When it was not immediately clear, the license identifier was
         confirmed with lawyers working with the Linux Foundation.
      
       - If there was any question as to the appropriate license identifier,
         the file was flagged for further research and to be revisited later
         in time.
      
      In total, over 70 hours of logged manual review was done on the
      spreadsheet to determine the SPDX license identifiers to apply to the
      source files by Kate, Philippe, Thomas and, in some cases, confirmation
      by lawyers working with the Linux Foundation.
      
      Kate also obtained a third independent scan of the 4.13 code base from
      FOSSology, and compared selected files where the other two scanners
      disagreed against that SPDX file, to see if there was new insights.  The
      Windriver scanner is based on an older version of FOSSology in part, so
      they are related.
      
      Thomas did random spot checks in about 500 files from the spreadsheets
      for the uapi headers and agreed with SPDX license identifier in the
      files he inspected. For the non-uapi files Thomas did random spot checks
      in about 15000 files.
      
      In initial set of patches against 4.14-rc6, 3 files were found to have
      copy/paste license identifier errors, and have been fixed to reflect the
      correct identifier.
      
      Additionally Philippe spent 10 hours this week doing a detailed manual
      inspection and review of the 12,461 patched files from the initial patch
      version early this week with:
       - a full scancode scan run, collecting the matched texts, detected
         license ids and scores
       - reviewing anything where there was a license detected (about 500+
         files) to ensure that the applied SPDX license was correct
       - reviewing anything where there was no detection but the patch license
         was not GPL-2.0 WITH Linux-syscall-note to ensure that the applied
         SPDX license was correct
      
      This produced a worksheet with 20 files needing minor correction.  This
      worksheet was then exported into 3 different .csv files for the
      different types of files to be modified.
      
      These .csv files were then reviewed by Greg.  Thomas wrote a script to
      parse the csv files and add the proper SPDX tag to the file, in the
      format that the file expected.  This script was further refined by Greg
      based on the output to detect more types of files automatically and to
      distinguish between header and source .c files (which need different
      comment types.)  Finally Greg ran the script using the .csv files to
      generate the patches.
      Reviewed-by: default avatarKate Stewart <kstewart@linuxfoundation.org>
      Reviewed-by: default avatarPhilippe Ombredanne <pombredanne@nexb.com>
      Reviewed-by: default avatarThomas Gleixner <tglx@linutronix.de>
      Signed-off-by: default avatarGreg Kroah-Hartman <gregkh@linuxfoundation.org>
      b2441318
  5. 09 Sep, 2017 1 commit
  6. 09 Dec, 2016 2 commits
    • Steven Rostedt (Red Hat)'s avatar
      tracing/fgraph: Have wakeup and irqsoff tracers ignore graph functions too · 1a414428
      Steven Rostedt (Red Hat) authored
      Currently both the wakeup and irqsoff traces do not handle set_graph_notrace
      well. The ftrace infrastructure will ignore the return paths of all
      functions leaving them hanging without an end:
      
        # echo '*spin*' > set_graph_notrace
        # cat trace
        [...]
                _raw_spin_lock() {
                  preempt_count_add() {
                  do_raw_spin_lock() {
                update_rq_clock();
      
      Where the '*spin*' functions should have looked like this:
      
                _raw_spin_lock() {
                  preempt_count_add();
                  do_raw_spin_lock();
                }
                update_rq_clock();
      
      Instead, have the wakeup and irqsoff tracers ignore the functions that are
      set by the set_graph_notrace like the function_graph tracer does. Move
      the logic in the function_graph tracer into a header to allow wakeup and
      irqsoff tracers to use it as well.
      
      Cc: Namhyung Kim <namhyung.kim@lge.com>
      Signed-off-by: default avatarSteven Rostedt <rostedt@goodmis.org>
      1a414428
    • Steven Rostedt (Red Hat)'s avatar
      fgraph: Handle a case where a tracer ignores set_graph_notrace · 794de08a
      Steven Rostedt (Red Hat) authored
      Both the wakeup and irqsoff tracers can use the function graph tracer when
      the display-graph option is set. The problem is that they ignore the notrace
      file, and record the entry of functions that would be ignored by the
      function_graph tracer. This causes the trace->depth to be recorded into the
      ring buffer. The set_graph_notrace uses a trick by adding a large negative
      number to the trace->depth when a graph function is to be ignored.
      
      On trace output, the graph function uses the depth to record a stack of
      functions. But since the depth is negative, it accesses the array with a
      negative number and causes an out of bounds access that can cause a kernel
      oops or corrupt data.
      
      Have the print functions handle cases where a tracer still records functions
      even when they are in set_graph_notrace.
      
      Also add warnings if the depth is below zero before accessing the array.
      
      Note, the function graph logic will still prevent the return of these
      functions from being recorded, which means that they will be left hanging
      without a return. For example:
      
         # echo '*spin*' > set_graph_notrace
         # echo 1 > options/display-graph
         # echo wakeup > current_tracer
         # cat trace
         [...]
            _raw_spin_lock() {
              preempt_count_add() {
              do_raw_spin_lock() {
            update_rq_clock();
      
      Where it should look like:
      
            _raw_spin_lock() {
              preempt_count_add();
              do_raw_spin_lock();
            }
            update_rq_clock();
      
      Cc: stable@vger.kernel.org
      Cc: Namhyung Kim <namhyung.kim@lge.com>
      Fixes: 29ad23b0 ("ftrace: Add set_graph_notrace filter")
      Signed-off-by: default avatarSteven Rostedt <rostedt@goodmis.org>
      794de08a
  7. 24 Nov, 2016 1 commit
  8. 01 Sep, 2016 2 commits
    • Namhyung Kim's avatar
      ftrace: Access ret_stack->subtime only in the function profiler · 8861dd30
      Namhyung Kim authored
      The subtime is used only for function profiler with function graph
      tracer enabled.  Move the definition of subtime under
      CONFIG_FUNCTION_PROFILER to reduce the memory usage.  Also move the
      initialization of subtime into the graph entry callback.
      
      Link: http://lkml.kernel.org/r/20160831025529.24018-1-namhyung@kernel.org
      
      Cc: Ingo Molnar <mingo@kernel.org>
      Cc: Josh Poimboeuf <jpoimboe@redhat.com>
      Signed-off-by: default avatarNamhyung Kim <namhyung@kernel.org>
      Signed-off-by: default avatarSteven Rostedt <rostedt@goodmis.org>
      8861dd30
    • Namhyung Kim's avatar
      function_graph: Handle TRACE_BPUTS in print_graph_comment · 613dccdf
      Namhyung Kim authored
      It missed to handle TRACE_BPUTS so messages recorded by trace_bputs()
      will be shown with symbol info unnecessarily.
      
      You can see it with the trace_printk sample code:
      
        # cd /sys/kernel/tracing/
        # echo sys_sync > set_graph_function
        # echo 1 > options/sym-offset
        # echo function_graph > current_tracer
      
      Note that the sys_sync filter was there to prevent recording other
      functions and the sym-offset option was needed since the first message
      was called from a module init function so kallsyms doesn't have the
      symbol and omitted in the output.
      
        # cd ~/build/kernel
        # insmod samples/trace_printk/trace-printk.ko
      
        # cd -
        # head trace
      
      Before:
      
        # tracer: function_graph
        #
        # CPU  DURATION                  FUNCTION CALLS
        # |     |   |                     |   |   |   |
         1)               |  /* 0xffffffffa0002000: This is a static string that will use trace_bputs */
         1)               |  /* This is a dynamic string that will use trace_puts */
         1)               |  /* trace_printk_irq_work+0x5/0x7b [trace_printk]: (irq) This is a static string that will use trace_bputs */
         1)               |  /* (irq) This is a dynamic string that will use trace_puts */
         1)               |  /* (irq) This is a static string that will use trace_bprintk() */
         1)               |  /* (irq) This is a dynamic string that will use trace_printk */
      
      After:
      
        # tracer: function_graph
        #
        # CPU  DURATION                  FUNCTION CALLS
        # |     |   |                     |   |   |   |
         1)               |  /* This is a static string that will use trace_bputs */
         1)               |  /* This is a dynamic string that will use trace_puts */
         1)               |  /* (irq) This is a static string that will use trace_bputs */
         1)               |  /* (irq) This is a dynamic string that will use trace_puts */
         1)               |  /* (irq) This is a static string that will use trace_bprintk() */
         1)               |  /* (irq) This is a dynamic string that will use trace_printk */
      
      Link: http://lkml.kernel.org/r/20160901024354.13720-1-namhyung@kernel.orgSigned-off-by: default avatarNamhyung Kim <namhyung@kernel.org>
      Signed-off-by: default avatarSteven Rostedt <rostedt@goodmis.org>
      613dccdf
  9. 24 Aug, 2016 4 commits
  10. 27 Jun, 2016 1 commit
  11. 20 Jun, 2016 1 commit
  12. 25 Mar, 2016 1 commit
  13. 22 Mar, 2016 1 commit
  14. 07 Nov, 2015 1 commit
  15. 30 Sep, 2015 2 commits
    • Steven Rostedt (Red Hat)'s avatar
      tracing: Move trace_flags from global to a trace_array field · 983f938a
      Steven Rostedt (Red Hat) authored
      In preparation to make trace options per instance, the global trace_flags
      needs to be moved from being a global variable to a field within the trace
      instance trace_array structure.
      
      There's still more work to do, as there's some functions that use
      trace_flags without passing in a way to get to the current_trace array. For
      those, the global_trace is used directly (from trace.c). This includes
      setting and clearing the trace_flags. This means that when a new instance is
      created, it just gets the trace_flags of the global_trace and will not be
      able to modify them. Depending on the functions that have access to the
      trace_array, the flags of an instance may not affect parts of its trace,
      where the global_trace is used. These will be fixed in future changes.
      Signed-off-by: default avatarSteven Rostedt <rostedt@goodmis.org>
      983f938a
    • Steven Rostedt (Red Hat)'s avatar
      tracing: Move sleep-time and graph-time options out of the core trace_flags · 55577204
      Steven Rostedt (Red Hat) authored
      The sleep-time and graph-time options are only for the function graph tracer
      and are not used by anything else. As tracer options are now visible when
      the tracer is not activated, its better to move the function graph specific
      tracer options into the function graph tracer.
      Signed-off-by: default avatarSteven Rostedt <rostedt@goodmis.org>
      55577204
  16. 21 Jul, 2015 1 commit
  17. 13 May, 2015 2 commits
  18. 16 Apr, 2015 1 commit
    • Rabin Vincent's avatar
      tracing: Handle ftrace_dump() atomic context in graph_trace_open() · ef99b88b
      Rabin Vincent authored
      graph_trace_open() can be called in atomic context from ftrace_dump().
      Use GFP_ATOMIC for the memory allocations when that's the case, in order
      to avoid the following splat.
      
       BUG: sleeping function called from invalid context at mm/slab.c:2849
       in_atomic(): 1, irqs_disabled(): 128, pid: 0, name: swapper/0
       Backtrace:
       ..
       [<8004dc94>] (__might_sleep) from [<801371f4>] (kmem_cache_alloc_trace+0x160/0x238)
        r7:87800040 r6:000080d0 r5:810d16e8 r4:000080d0
       [<80137094>] (kmem_cache_alloc_trace) from [<800cbd60>] (graph_trace_open+0x30/0xd0)
        r10:00000100 r9:809171a8 r8:00008e28 r7:810d16f0 r6:00000001 r5:810d16e8
        r4:810d16f0
       [<800cbd30>] (graph_trace_open) from [<800c79c4>] (trace_init_global_iter+0x50/0x9c)
        r8:00008e28 r7:808c853c r6:00000001 r5:810d16e8 r4:810d16f0 r3:800cbd30
       [<800c7974>] (trace_init_global_iter) from [<800c7aa0>] (ftrace_dump+0x90/0x2ec)
        r4:810d2580 r3:00000000
       [<800c7a10>] (ftrace_dump) from [<80414b2c>] (sysrq_ftrace_dump+0x1c/0x20)
        r10:00000100 r9:809171a8 r8:808f6e7c r7:00000001 r6:00000007 r5:0000007a
        r4:808d5394
       [<80414b10>] (sysrq_ftrace_dump) from [<800169b8>] (return_to_handler+0x0/0x18)
       [<80415498>] (__handle_sysrq) from [<800169b8>] (return_to_handler+0x0/0x18)
        r8:808c8100 r7:808c8444 r6:00000101 r5:00000010 r4:84eb3210
       [<80415668>] (handle_sysrq) from [<800169b8>] (return_to_handler+0x0/0x18)
       [<8042a760>] (pl011_int) from [<800169b8>] (return_to_handler+0x0/0x18)
        r10:809171bc r9:809171a8 r8:00000001 r7:00000026 r6:808c6000 r5:84f01e60
        r4:8454fe00
       [<8007782c>] (handle_irq_event_percpu) from [<80077b44>] (handle_irq_event+0x4c/0x6c)
        r10:808c7ef0 r9:87283e00 r8:00000001 r7:00000000 r6:8454fe00 r5:84f01e60
        r4:84f01e00
       [<80077af8>] (handle_irq_event) from [<8007aa28>] (handle_fasteoi_irq+0xf0/0x1ac)
        r6:808f52a4 r5:84f01e60 r4:84f01e00 r3:00000000
       [<8007a938>] (handle_fasteoi_irq) from [<80076dc0>] (generic_handle_irq+0x3c/0x4c)
        r6:00000026 r5:00000000 r4:00000026 r3:8007a938
       [<80076d84>] (generic_handle_irq) from [<80077128>] (__handle_domain_irq+0x8c/0xfc)
        r4:808c1e38 r3:0000002e
       [<8007709c>] (__handle_domain_irq) from [<800087b8>] (gic_handle_irq+0x34/0x6c)
        r10:80917748 r9:00000001 r8:88802100 r7:808c7ef0 r6:808c8fb0 r5:00000015
        r4:8880210c r3:808c7ef0
       [<80008784>] (gic_handle_irq) from [<80014044>] (__irq_svc+0x44/0x7c)
      
      Link: http://lkml.kernel.org/r/1428953721-31349-1-git-send-email-rabin@rab.in
      Link: http://lkml.kernel.org/r/1428957012-2319-1-git-send-email-rabin@rab.in
      
      Cc: stable@vger.kernel.org # 3.13+
      Signed-off-by: default avatarRabin Vincent <rabin@rab.in>
      Signed-off-by: default avatarSteven Rostedt <rostedt@goodmis.org>
      ef99b88b
  19. 03 Feb, 2015 1 commit
    • Steven Rostedt (Red Hat)'s avatar
      tracing: Convert the tracing facility over to use tracefs · 8434dc93
      Steven Rostedt (Red Hat) authored
      debugfs was fine for the tracing facility as a quick way to get
      an interface. Now that tracing has matured, it should separate itself
      from debugfs such that it can be mounted separately without needing
      to mount all of debugfs with it. That is, users resist using tracing
      because it requires mounting debugfs. Having tracing have its own file
      system lets users get the features of tracing without needing to bring
      in the rest of the kernel's debug infrastructure.
      
      Another reason for tracefs is that debubfs does not support mkdir.
      Currently, to create instances, one does a mkdir in the tracing/instance
      directory. This is implemented via a hack that forces debugfs to do
      something it is not intended on doing. By converting over to tracefs, this
      hack can be removed and mkdir can be properly implemented. This patch does
      not address this yet, but it lays the ground work for that to be done.
      Signed-off-by: default avatarSteven Rostedt <rostedt@goodmis.org>
      8434dc93
  20. 22 Jan, 2015 1 commit
  21. 03 Dec, 2014 1 commit
    • Byungchul Park's avatar
      tracing: Add additional marks to signal very large time deltas · 8e1e1df2
      Byungchul Park authored
      Currently, function graph tracer prints "!" or "+" just before
      function execution time to signal a function overhead, depending
      on the time. And some tracers tracing latency also print "!" or
      "+" just after time to signal overhead, depending on the interval
      between events. Even it is usually enough to do that, we sometimes
      need to signal for bigger execution time than 100 micro seconds.
      
      For example, I used function graph tracer to detect if there is
      any case that exit_mm() takes too much time. I did following steps
      in /sys/kernel/debug/tracing. It was easier to detect very large
      excution time with patched kernel than with original kernel.
      
      $ echo exit_mm > set_graph_function
      $ echo function_graph > current_tracer
      $ echo > trace
      $ cat trace_pipe > $LOGFILE
       ... (do something and terminate logging)
      $ grep "\\$" $LOGFILE
       3) $ 22082032 us |                      } /* kernel_map_pages */
       3) $ 22082040 us |                    } /* free_pages_prepare */
       3) $ 22082113 us |                  } /* free_hot_cold_page */
       3) $ 22083455 us |                } /* free_hot_cold_page_list */
       3) $ 22083895 us |              } /* release_pages */
       3) $ 22177873 us |            } /* free_pages_and_swap_cache */
       3) $ 22178929 us |          } /* unmap_single_vma */
       3) $ 22198885 us |        } /* unmap_vmas */
       3) $ 22206949 us |      } /* exit_mmap */
       3) $ 22207659 us |    } /* mmput */
       3) $ 22207793 us |  } /* exit_mm */
      
      And then, it was easy to find out that a schedule-out occured by
      sub_preempt_count() within kernel_map_pages().
      
      To detect very large function exection time caused by either problematic
      function implementation or scheduling issues, this patch can be useful.
      
      Link: http://lkml.kernel.org/r/1416789259-24038-1-git-send-email-byungchul.park@lge.comSigned-off-by: default avatarByungchul Park <byungchul.park@lge.com>
      Signed-off-by: default avatarSteven Rostedt <rostedt@goodmis.org>
      8e1e1df2
  22. 20 Nov, 2014 2 commits
  23. 19 Nov, 2014 1 commit
  24. 14 Nov, 2014 4 commits
  25. 19 Jul, 2014 1 commit
  26. 18 Jul, 2014 2 commits
  27. 17 Jul, 2014 1 commit
    • Steven Rostedt (Red Hat)'s avatar
      ftrace-graph: Remove dependency of ftrace_stop() from ftrace_graph_stop() · 1b2f121c
      Steven Rostedt (Red Hat) authored
      ftrace_stop() is going away as it disables parts of function tracing
      that affects users that should not be affected. But ftrace_graph_stop()
      is built on ftrace_stop(). Here's another example of killing all of
      function tracing because something went wrong with function graph
      tracing.
      
      Instead of disabling all users of function tracing on function graph
      error, disable only function graph tracing.
      
      A new function is created called ftrace_graph_is_dead(). This is called
      in strategic paths to prevent function graph from doing more harm and
      allowing at least a warning to be printed before the system crashes.
      
      NOTE: ftrace_stop() is still used until all the archs are converted over
      to use ftrace_graph_is_dead(). After that, ftrace_stop() will be removed.
      Reviewed-by: default avatarMasami Hiramatsu <masami.hiramatsu.pt@hitachi.com>
      Cc: Frederic Weisbecker <fweisbec@gmail.com>
      Signed-off-by: default avatarSteven Rostedt <rostedt@goodmis.org>
      1b2f121c
  28. 21 May, 2014 1 commit