This patch reverts upstream commit 978defee11a5 ("tracing: Do a WARN_ON()
if start_thread() in hwlat is called when thread exists")
.start hook can be legally called several times if according
tracer is stopped
screen window 1
[root@localhost ~]# echo 1 > /sys/kernel/tracing/events/kmem/kfree/enable
[root@localhost ~]# echo 1 > /sys/kernel/tracing/options/pause-on-trace
[root@localhost ~]# less -F /sys/kernel/tracing/trace
screen window 2
[root@localhost ~]# cat /sys/kernel/debug/tracing/tracing_on
0
[root@localhost ~]# echo hwlat > /sys/kernel/debug/tracing/current_tracer
[root@localhost ~]# echo 1 > /sys/kernel/debug/tracing/tracing_on
[root@localhost ~]# cat /sys/kernel/debug/tracing/tracing_on
0
[root@localhost ~]# echo 2 > /sys/kernel/debug/tracing/tracing_on
triggers warning in dmesg:
WARNING: CPU: 3 PID: 1403 at kernel/trace/trace_hwlat.c:371
hwlat_tracer_start+0xc9/0xd0
Fixes: 978defee11a5 ("tracing: Do a WARN_ON() if start_thread() in hwlat is
called when thread exists")
Patch was sent to upstream but is not approved yet.
https://jira.sw.ru/browse/PSBM-120940
Signed-off-by: Vasily Averin <v...@virtuozzo.com>
---
kernel/trace/trace_hwlat.c | 2 +-
1 file changed, 1 insertion(+), 1 deletion(-)
diff --git a/kernel/trace/trace_hwlat.c b/kernel/trace/trace_hwlat.c
index 45a9e3b..12b8bd7 100644
--- a/kernel/trace/trace_hwlat.c
+++ b/kernel/trace/trace_hwlat.c
@@ -368,7 +368,7 @@ static int start_kthread(struct trace_array *tr)
{
struct task_struct *kthread;
- if (WARN_ON(hwlat_kthread))
+ if (hwlat_kthread)
return 0;
kthread = kthread_create(kthread_fn, NULL, "hwlatd");
--
1.8.3.1
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