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authorSteven Rostedt (VMware) <rostedt@goodmis.org>2018-08-01 21:40:57 +0200
committerSteven Rostedt (VMware) <rostedt@goodmis.org>2018-08-01 22:01:02 +0200
commitf143641bfef9a4a60c57af30de26c63057e7e695 (patch)
tree6d1bfaf1544530bee0ae1b60336766d3d2823525 /kernel
parenttracefs: Annotate tracefs_ops with __ro_after_init (diff)
downloadlinux-f143641bfef9a4a60c57af30de26c63057e7e695.tar.xz
linux-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>
Diffstat (limited to 'kernel')
-rw-r--r--kernel/trace/trace.c4
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);