releases/4.14.48/tracing-make-the-snapshot-trigger-work-with-instances.patch

   1 From 2824f5033248600673e3e126a4d135363cbfd9ac Mon Sep 17 00:00:00 2001
   2 From: "Steven Rostedt (VMware)" <rostedt@goodmis.org>
   3 Date: Mon, 28 May 2018 10:56:36 -0400
   4 Subject: tracing: Make the snapshot trigger work with instances
   5
   6 From: Steven Rostedt (VMware) <rostedt@goodmis.org>
   7
   8 commit 2824f5033248600673e3e126a4d135363cbfd9ac upstream.
   9
  10 The snapshot trigger currently only affects the main ring buffer, even when
  11 it is used by the instances. This can be confusing as the snapshot trigger
  12 is listed in the instance.
  13
  14  > # cd /sys/kernel/tracing
  15  > # mkdir instances/foo
  16  > # echo snapshot > instances/foo/events/syscalls/sys_enter_fchownat/trigger
  17  > # echo top buffer > trace_marker
  18  > # echo foo buffer > instances/foo/trace_marker
  19  > # touch /tmp/bar
  20  > # chown rostedt /tmp/bar
  21  > # cat instances/foo/snapshot
  22  # tracer: nop
  23  #
  24  #
  25  # * Snapshot is freed *
  26  #
  27  # Snapshot commands:
  28  # echo 0 > snapshot : Clears and frees snapshot buffer
  29  # echo 1 > snapshot : Allocates snapshot buffer, if not already allocated.
  30  #                      Takes a snapshot of the main buffer.
  31  # echo 2 > snapshot : Clears snapshot buffer (but does not allocate or free)
  32  #                      (Doesn't have to be '2' works with any number that
  33  #                       is not a '0' or '1')
  34
  35  > # cat snapshot
  36  # tracer: nop
  37  #
  38  #                              _-----=> irqs-off
  39  #                             / _----=> need-resched
  40  #                            | / _---=> hardirq/softirq
  41  #                            || / _--=> preempt-depth
  42  #                            ||| /     delay
  43  #           TASK-PID   CPU#  ||||    TIMESTAMP  FUNCTION
  44  #              | |       |   ||||       |         |
  45              bash-1189  [000] ....   111.488323: tracing_mark_write: top buffer
  46
  47 Not only did the snapshot occur in the top level buffer, but the instance
  48 snapshot buffer should have been allocated, and it is still free.
  49
  50 Cc: stable@vger.kernel.org
  51 Fixes: 85f2b08268c01 ("tracing: Add basic event trigger framework")
  52 Signed-off-by: Steven Rostedt (VMware) <rostedt@goodmis.org>
  53 Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>
  54
  55 ---
  56  kernel/trace/trace.c                |   12 ++++++------
  57  kernel/trace/trace.h                |   11 +++++++++++
  58  kernel/trace/trace_events_trigger.c |   10 ++++++++--
  59  3 files changed, 25 insertions(+), 8 deletions(-)
  60
  61 --- a/kernel/trace/trace.c
  62 +++ b/kernel/trace/trace.c
  63 @@ -894,7 +894,7 @@ int __trace_bputs(unsigned long ip, cons
  64  EXPORT_SYMBOL_GPL(__trace_bputs);
  65
  66  #ifdef CONFIG_TRACER_SNAPSHOT
  67 -static void tracing_snapshot_instance(struct trace_array *tr)
  68 +void tracing_snapshot_instance(struct trace_array *tr)
  69  {
  70         struct tracer *tracer = tr->current_trace;
  71         unsigned long flags;
  72 @@ -950,7 +950,7 @@ static int resize_buffer_duplicate_size(
  73                                         struct trace_buffer *size_buf, int cpu_id);
  74  static void set_buffer_entries(struct trace_buffer *buf, unsigned long val);
  75
  76 -static int alloc_snapshot(struct trace_array *tr)
  77 +int tracing_alloc_snapshot_instance(struct trace_array *tr)
  78  {
  79         int ret;
  80
  81 @@ -996,7 +996,7 @@ int tracing_alloc_snapshot(void)
  82         struct trace_array *tr = &global_trace;
  83         int ret;
  84
  85 -       ret = alloc_snapshot(tr);
  86 +       ret = tracing_alloc_snapshot_instance(tr);
  87         WARN_ON(ret < 0);
  88
  89         return ret;
  90 @@ -5400,7 +5400,7 @@ static int tracing_set_tracer(struct tra
  91
  92  #ifdef CONFIG_TRACER_MAX_TRACE
  93         if (t->use_max_tr && !had_max_tr) {
  94 -               ret = alloc_snapshot(tr);
  95 +               ret = tracing_alloc_snapshot_instance(tr);
  96                 if (ret < 0)
  97                         goto out;
  98         }
  99 @@ -6378,7 +6378,7 @@ tracing_snapshot_write(struct file *filp
 100                 }
 101  #endif
 102                 if (!tr->allocated_snapshot) {
 103 -                       ret = alloc_snapshot(tr);
 104 +                       ret = tracing_alloc_snapshot_instance(tr);
 105                         if (ret < 0)
 106                                 break;
 107                 }
 108 @@ -7099,7 +7099,7 @@ ftrace_trace_snapshot_callback(struct tr
 109                 return ret;
 110
 111   out_reg:
 112 -       ret = alloc_snapshot(tr);
 113 +       ret = tracing_alloc_snapshot_instance(tr);
 114         if (ret < 0)
 115                 goto out;
 116
 117 --- a/kernel/trace/trace.h
 118 +++ b/kernel/trace/trace.h
 119 @@ -1807,6 +1807,17 @@ static inline void __init trace_event_in
 120  static inline void trace_event_eval_update(struct trace_eval_map **map, int len) { }
 121  #endif
 122
 123 +#ifdef CONFIG_TRACER_SNAPSHOT
 124 +void tracing_snapshot_instance(struct trace_array *tr);
 125 +int tracing_alloc_snapshot_instance(struct trace_array *tr);
 126 +#else
 127 +static inline void tracing_snapshot_instance(struct trace_array *tr) { }
 128 +static inline int tracing_alloc_snapshot_instance(struct trace_array *tr)
 129 +{
 130 +       return 0;
 131 +}
 132 +#endif
 133 +
 134  extern struct trace_iterator *tracepoint_print_iter;
 135
 136  #endif /* _LINUX_KERNEL_TRACE_H */
 137 --- a/kernel/trace/trace_events_trigger.c
 138 +++ b/kernel/trace/trace_events_trigger.c
 139 @@ -642,6 +642,7 @@ event_trigger_callback(struct event_comm
 140         trigger_data->count = -1;
 141         trigger_data->ops = trigger_ops;
 142         trigger_data->cmd_ops = cmd_ops;
 143 +       trigger_data->private_data = file;
 144         INIT_LIST_HEAD(&trigger_data->list);
 145         INIT_LIST_HEAD(&trigger_data->named_list);
 146
 147 @@ -1042,7 +1043,12 @@ static struct event_command trigger_trac
 148  static void
 149  snapshot_trigger(struct event_trigger_data *data, void *rec)
 150  {
 151 -       tracing_snapshot();
 152 +       struct trace_event_file *file = data->private_data;
 153 +
 154 +       if (file)
 155 +               tracing_snapshot_instance(file->tr);
 156 +       else
 157 +               tracing_snapshot();
 158  }
 159
 160  static void
 161 @@ -1064,7 +1070,7 @@ register_snapshot_trigger(char *glob, st
 162  {
 163         int ret = register_trigger(glob, ops, data, file);
 164
 165 -       if (ret > 0 && tracing_alloc_snapshot() != 0) {
 166 +       if (ret > 0 && tracing_alloc_snapshot_instance(file->tr) != 0) {
 167                 unregister_trigger(glob, ops, data, file);
 168                 ret = 0;
 169         }