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| author | Steven Rostedt (VMware) <rostedt@goodmis.org> | 2018-08-01 15:40:57 -0400 |
|---|---|---|
| committer | Steven Rostedt (VMware) <rostedt@goodmis.org> | 2018-08-01 16:01:02 -0400 |
| commit | f143641bfef9a4a60c57af30de26c63057e7e695 (patch) | |
| tree | 6d1bfaf1544530bee0ae1b60336766d3d2823525 | |
| parent | 5248ee85603067e62a228402afd2fb68f957746b (diff) | |
| download | linux-stable-f143641bfef9a4a60c57af30de26c63057e7e695.tar.gz linux-stable-f143641bfef9a4a60c57af30de26c63057e7e695.tar.bz2 linux-stable-f143641bfef9a4a60c57af30de26c63057e7e695.zip | |
tracing: Do not call start/stop() functions when tracing_on does not change
Currently, when one echo's in 1 into tracing_on, the current tracer's
"start()" function is executed, even if tracing_on was already one. This can
lead to strange side effects. One being that if the hwlat tracer is enabled,
and someone does "echo 1 > tracing_on" into tracing_on, the hwlat tracer's
start() function is called again which will recreate another kernel thread,
and make it unable to remove the old one.
Link: http://lkml.kernel.org/r/1533120354-22923-1-git-send-email-erica.bugden@linutronix.de
Cc: stable@vger.kernel.org
Fixes: 2df8f8a6a897e ("tracing: Fix regression with irqsoff tracer and tracing_on file")
Reported-by: Erica Bugden <erica.bugden@linutronix.de>
Signed-off-by: Steven Rostedt (VMware) <rostedt@goodmis.org>
| -rw-r--r-- | kernel/trace/trace.c | 4 |
1 files changed, 3 insertions, 1 deletions
diff --git a/kernel/trace/trace.c b/kernel/trace/trace.c index 823687997b01..2378bb4f1442 100644 --- a/kernel/trace/trace.c +++ b/kernel/trace/trace.c @@ -7628,7 +7628,9 @@ rb_simple_write(struct file *filp, const char __user *ubuf, if (buffer) { mutex_lock(&trace_types_lock); - if (val) { + if (!!val == tracer_tracing_is_on(tr)) { + val = 0; /* do nothing */ + } else if (val) { tracer_tracing_on(tr); if (tr->current_trace->start) tr->current_trace->start(tr); |