diff options
author | Xiao Yang <yangx.jy@cn.fujitsu.com> | 2020-04-14 09:51:45 +0800 |
---|---|---|
committer | Greg Kroah-Hartman <gregkh@linuxfoundation.org> | 2020-04-24 07:59:06 +0200 |
commit | a289fd864722dcf5363fec66a35965d4964df515 (patch) | |
tree | 1c0c89fcfe401dc686b2c379c5d3371682f38626 | |
parent | 5fadf30330d9dd4725d57cf06e7799c1f9c69edf (diff) |
tracing: Fix the race between registering 'snapshot' event trigger and triggering 'snapshot' operation
commit 0bbe7f719985efd9adb3454679ecef0984cb6800 upstream.
Traced event can trigger 'snapshot' operation(i.e. calls snapshot_trigger()
or snapshot_count_trigger()) when register_snapshot_trigger() has completed
registration but doesn't allocate buffer for 'snapshot' event trigger. In
the rare case, 'snapshot' operation always detects the lack of allocated
buffer so make register_snapshot_trigger() allocate buffer first.
trigger-snapshot.tc in kselftest reproduces the issue on slow vm:
-----------------------------------------------------------
cat trace
...
ftracetest-3028 [002] .... 236.784290: sched_process_fork: comm=ftracetest pid=3028 child_comm=ftracetest child_pid=3036
<...>-2875 [003] .... 240.460335: tracing_snapshot_instance_cond: *** SNAPSHOT NOT ALLOCATED ***
<...>-2875 [003] .... 240.460338: tracing_snapshot_instance_cond: *** stopping trace here! ***
-----------------------------------------------------------
Link: http://lkml.kernel.org/r/20200414015145.66236-1-yangx.jy@cn.fujitsu.com
Cc: stable@vger.kernel.org
Fixes: 93e31ffbf417a ("tracing: Add 'snapshot' event trigger command")
Signed-off-by: Xiao Yang <yangx.jy@cn.fujitsu.com>
Signed-off-by: Steven Rostedt (VMware) <rostedt@goodmis.org>
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>
-rw-r--r-- | kernel/trace/trace_events_trigger.c | 10 |
1 files changed, 3 insertions, 7 deletions
diff --git a/kernel/trace/trace_events_trigger.c b/kernel/trace/trace_events_trigger.c index 8a88e85c8c61..c9ca2ed50c0e 100644 --- a/kernel/trace/trace_events_trigger.c +++ b/kernel/trace/trace_events_trigger.c @@ -1068,14 +1068,10 @@ register_snapshot_trigger(char *glob, struct event_trigger_ops *ops, struct event_trigger_data *data, struct trace_event_file *file) { - int ret = register_trigger(glob, ops, data, file); - - if (ret > 0 && tracing_alloc_snapshot() != 0) { - unregister_trigger(glob, ops, data, file); - ret = 0; - } + if (tracing_alloc_snapshot() != 0) + return 0; - return ret; + return register_trigger(glob, ops, data, file); } static int |