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 10:32:35 +0200 |
commit | b0d32c7b0cdadf1ebe7953f02453c3dfa9353df5 (patch) | |
tree | 09fe541187c06d3d30ccc229588e7920893b9333 /kernel | |
parent | 187bee9b94fb2ddaea6fb703e70f41b6e1dffaed (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>
Diffstat (limited to 'kernel')
-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 176debd3481b..ddae35127571 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); |