perf_events, trace: Fix probe unregister race

tracepoint_probe_unregister() does not synchronize against the probe
callbacks, so do that explicitly. This properly serializes the callbacks
and the free of the data used therein.

Also, use this_cpu_ptr() where possible.

Acked-by: Frederic Weisbecker <fweisbec@gmail.com>
Signed-off-by: Peter Zijlstra <a.p.zijlstra@chello.nl>
LKML-Reference: <1274438476.1674.1702.camel@laptop>
Signed-off-by: Ingo Molnar <mingo@elte.hu>

1 files changed, 8 insertions, 2 deletions

diff --git a/kernel/trace/trace_event_perf.c b/kernel/trace/trace_event_perf.c
index cb6f365016e4..49c7abf2ba5c 100644
--- a/kernel/trace/trace_event_perf.c
+++ b/kernel/trace/trace_event_perf.c
@@ -116,7 +116,7 @@ int perf_trace_enable(struct perf_event *p_event)
         if (WARN_ON_ONCE(!list))
                 return -EINVAL;
 
-        list = per_cpu_ptr(list, smp_processor_id());
+        list = this_cpu_ptr(list);
         hlist_add_head_rcu(&p_event->hlist_entry, list);
 
         return 0;
@@ -142,6 +142,12 @@ void perf_trace_destroy(struct perf_event *p_event)
                                             tp_event->class->perf_probe,
                                             tp_event);
 
+        /*
+         * Ensure our callback won't be called anymore. See
+         * tracepoint_probe_unregister() and __DO_TRACE().
+         */
+        synchronize_sched();
+
         free_percpu(tp_event->perf_events);
         tp_event->perf_events = NULL;
 
@@ -169,7 +175,7 @@ __kprobes void *perf_trace_buf_prepare(int size, unsigned short type,
         if (*rctxp < 0)
                 return NULL;
 
-        raw_data = per_cpu_ptr(perf_trace_buf[*rctxp], smp_processor_id());
+        raw_data = this_cpu_ptr(perf_trace_buf[*rctxp]);
 
         /* zero the dead bytes from align to not leak stack to user */
         memset(&raw_data[size - sizeof(u64)], 0, sizeof(u64));