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authorLi Zefan <lizf@cn.fujitsu.com>2009-05-06 10:33:45 +0800
committerIngo Molnar <mingo@elte.hu>2009-05-06 10:38:19 +0200
commit20c8928abe70e204bd077ab6cfe23002d7788983 (patch)
treee161656f99c814ebdd69df8b5a79dab58f80065e /kernel/trace/trace_event_profile.c
parent2df75e415709ad12862028916c772c1f377f6a7c (diff)
downloadlinux-20c8928abe70e204bd077ab6cfe23002d7788983.tar.bz2
tracing/events: fix concurrent access to ftrace_events list
A module will add/remove its trace events when it gets loaded/unloaded, so the ftrace_events list is not "const", and concurrent access needs to be protected. This patch thus fixes races between loading/unloding modules and read 'available_events' or read/write 'set_event', etc. Below shows how to reproduce the race: # for ((; ;)) { cat /mnt/tracing/available_events; } > /dev/null & # for ((; ;)) { insmod trace-events-sample.ko; rmmod sample; } & After a while: BUG: unable to handle kernel paging request at 0010011c IP: [<c1080f27>] t_next+0x1b/0x2d ... Call Trace: [<c10c90e6>] ? seq_read+0x217/0x30d [<c10c8ecf>] ? seq_read+0x0/0x30d [<c10b4c19>] ? vfs_read+0x8f/0x136 [<c10b4fc3>] ? sys_read+0x40/0x65 [<c1002a68>] ? sysenter_do_call+0x12/0x36 [ Impact: fix races when concurrent accessing ftrace_events list ] Signed-off-by: Li Zefan <lizf@cn.fujitsu.com> Acked-by: Steven Rostedt <rostedt@goodmis.org> Acked-by: Frederic Weisbecker <fweisbec@gmail.com> Cc: Tom Zanussi <tzanussi@gmail.com> Cc: Peter Zijlstra <a.p.zijlstra@chello.nl> LKML-Reference: <4A00F709.3080800@cn.fujitsu.com> Signed-off-by: Ingo Molnar <mingo@elte.hu>
Diffstat (limited to 'kernel/trace/trace_event_profile.c')
-rw-r--r--kernel/trace/trace_event_profile.c19
1 files changed, 14 insertions, 5 deletions
diff --git a/kernel/trace/trace_event_profile.c b/kernel/trace/trace_event_profile.c
index 7bf2ad65eee5..5b5895afecfe 100644
--- a/kernel/trace/trace_event_profile.c
+++ b/kernel/trace/trace_event_profile.c
@@ -10,21 +10,30 @@
int ftrace_profile_enable(int event_id)
{
struct ftrace_event_call *event;
+ int ret = -EINVAL;
+ mutex_lock(&event_mutex);
list_for_each_entry(event, &ftrace_events, list) {
- if (event->id == event_id)
- return event->profile_enable(event);
+ if (event->id == event_id) {
+ ret = event->profile_enable(event);
+ break;
+ }
}
+ mutex_unlock(&event_mutex);
- return -EINVAL;
+ return ret;
}
void ftrace_profile_disable(int event_id)
{
struct ftrace_event_call *event;
+ mutex_lock(&event_mutex);
list_for_each_entry(event, &ftrace_events, list) {
- if (event->id == event_id)
- return event->profile_disable(event);
+ if (event->id == event_id) {
+ event->profile_disable(event);
+ break;
+ }
}
+ mutex_unlock(&event_mutex);
}