diff options
| author | Vasily Averin <vvs@virtuozzo.com> | 2020-01-24 10:03:06 +0300 |
|---|---|---|
| committer | Steven Rostedt (VMware) <rostedt@goodmis.org> | 2020-01-30 09:46:27 -0500 |
| commit | 6722b23e7a2ace078344064a9735fb73e554e9ef (patch) | |
| tree | 620ea409b5995754f5cb2c1ebe68170883c56647 | |
| parent | 039958a5f7aad695d4d52683c7d48aa13fb18249 (diff) | |
| download | talos-op-linux-6722b23e7a2ace078344064a9735fb73e554e9ef.tar.gz talos-op-linux-6722b23e7a2ace078344064a9735fb73e554e9ef.zip | |
trigger_next should increase position index
if seq_file .next fuction does not change position index,
read after some lseek can generate unexpected output.
Without patch:
# dd bs=30 skip=1 if=/sys/kernel/tracing/events/sched/sched_switch/trigger
dd: /sys/kernel/tracing/events/sched/sched_switch/trigger: cannot skip to specified offset
n traceoff snapshot stacktrace enable_event disable_event enable_hist disable_hist hist
# Available triggers:
# traceon traceoff snapshot stacktrace enable_event disable_event enable_hist disable_hist hist
6+1 records in
6+1 records out
206 bytes copied, 0.00027916 s, 738 kB/s
Notice the printing of "# Available triggers:..." after the line.
With the patch:
# dd bs=30 skip=1 if=/sys/kernel/tracing/events/sched/sched_switch/trigger
dd: /sys/kernel/tracing/events/sched/sched_switch/trigger: cannot skip to specified offset
n traceoff snapshot stacktrace enable_event disable_event enable_hist disable_hist hist
2+1 records in
2+1 records out
88 bytes copied, 0.000526867 s, 167 kB/s
It only prints the end of the file, and does not restart.
Link: http://lkml.kernel.org/r/3c35ee24-dd3a-8119-9c19-552ed253388a@virtuozzo.com
https://bugzilla.kernel.org/show_bug.cgi?id=206283
Signed-off-by: Vasily Averin <vvs@virtuozzo.com>
Signed-off-by: Steven Rostedt (VMware) <rostedt@goodmis.org>
| -rw-r--r-- | kernel/trace/trace_events_trigger.c | 5 |
1 files changed, 3 insertions, 2 deletions
diff --git a/kernel/trace/trace_events_trigger.c b/kernel/trace/trace_events_trigger.c index 60959c31791d..dd34a1b46a86 100644 --- a/kernel/trace/trace_events_trigger.c +++ b/kernel/trace/trace_events_trigger.c @@ -116,9 +116,10 @@ static void *trigger_next(struct seq_file *m, void *t, loff_t *pos) { struct trace_event_file *event_file = event_file_data(m->private); - if (t == SHOW_AVAILABLE_TRIGGERS) + if (t == SHOW_AVAILABLE_TRIGGERS) { + (*pos)++; return NULL; - + } return seq_list_next(t, &event_file->triggers, pos); } |
