diff options
| author | Steven Rostedt (VMware) <rostedt@goodmis.org> | 2018-08-01 15:40:57 -0400 |
|---|---|---|
| committer | Greg Kroah-Hartman <gregkh@linuxfoundation.org> | 2018-09-09 20:01:22 +0200 |
| commit | dc697314056cbf0f4b9ff2432c617edbebce1107 (patch) | |
| tree | d7d2b608070e5f1ecdb07271bad91e08c6d07637 | |
| parent | 4e935c2eaec5182ade1bac3d12b115e2f195a069 (diff) | |
tracing: Do not call start/stop() functions when tracing_on does not change
commit f143641bfef9a4a60c57af30de26c63057e7e695 upstream.
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>
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.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 148c2210a2b8..a47339b156ce 100644 --- a/kernel/trace/trace.c +++ b/kernel/trace/trace.c @@ -6920,7 +6920,9 @@ 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); |