[PATCH] Tracepoints fix reentrancy

[Mathieu Desnoyers <mathieu.desnoyers@polymtl.ca>]

The tracepoints had the same problem markers did have wrt reentrancy. Apply a
similar fix using a rcu_barrier after each tracepoint mutex lock.

Signed-off-by: Mathieu Desnoyers <mathieu.desnoyers@polymtl.ca>
CC: Ingo Molnar <mingo@elte.hu>
CC: "Frank Ch. Eigler" <fche@redhat.com>
CC: Lai Jiangshan <laijs@cn.fujitsu.com>
---
 kernel/tracepoint.c |    4 ++++
 1 file changed, 4 insertions(+)

Index: linux-2.6-lttng/kernel/tracepoint.c
===================================================================
--- linux-2.6-lttng.orig/kernel/tracepoint.c	2008-09-30 01:38:39.000000000 -0400
+++ linux-2.6-lttng/kernel/tracepoint.c	2008-09-30 01:39:56.000000000 -0400
@@ -361,6 +361,8 @@ int tracepoint_probe_register(const char
 	mutex_lock(&tracepoints_mutex);
 	entry = get_tracepoint(name);
 	WARN_ON(!entry);
+	if (entry->rcu_pending)
+		rcu_barrier_sched();
 	tracepoint_entry_free_old(entry, old);
 end:
 	mutex_unlock(&tracepoints_mutex);
@@ -397,6 +399,8 @@ int tracepoint_probe_unregister(const ch
 	entry = get_tracepoint(name);
 	if (!entry)
 		goto end;
+	if (entry->rcu_pending)
+		rcu_barrier_sched();
 	tracepoint_entry_free_old(entry, old);
 	remove_tracepoint(name);	/* Ignore busy error message */
 	ret = 0;
-- 
Mathieu Desnoyers
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