[patch 02/16] Marker fix unregister

[Mathieu Desnoyers]

get_marker() can return a NULL entry because the mutex is released in the middle
of those functions. Make sure we check to see if it has been concurrently
removed.

Impact: Bugfix.

Signed-off-by: Mathieu Desnoyers <mathieu.desnoyers@xxxxxxxxxx>
CC: Lai Jiangshan <laijs@xxxxxxxxxxxxxx>
---
 kernel/marker.c |   12 +++++++-----
 1 file changed, 7 insertions(+), 5 deletions(-)

Index: linux.trees.git/kernel/marker.c
===================================================================
--- linux.trees.git.orig/kernel/marker.c	2008-11-14 17:38:39.000000000 -0500
+++ linux.trees.git/kernel/marker.c	2008-11-14 17:38:43.000000000 -0500
@@ -653,10 +653,11 @@ int marker_probe_register(const char *na
 		goto end;
 	}
 	mutex_unlock(&markers_mutex);
-	marker_update_probes();		/* may update entry */
+	marker_update_probes();
 	mutex_lock(&markers_mutex);
 	entry = get_marker(name);
-	WARN_ON(!entry);
+	if (!entry)
+		goto end;
 	if (entry->rcu_pending)
 		rcu_barrier_sched();
 	entry->oldptr = old;
@@ -697,7 +698,7 @@ int marker_probe_unregister(const char *
 		rcu_barrier_sched();
 	old = marker_entry_remove_probe(entry, probe, probe_private);
 	mutex_unlock(&markers_mutex);
-	marker_update_probes();		/* may update entry */
+	marker_update_probes();
 	mutex_lock(&markers_mutex);
 	entry = get_marker(name);
 	if (!entry)
@@ -778,10 +779,11 @@ int marker_probe_unregister_private_data
 		rcu_barrier_sched();
 	old = marker_entry_remove_probe(entry, NULL, probe_private);
 	mutex_unlock(&markers_mutex);
-	marker_update_probes();		/* may update entry */
+	marker_update_probes();
 	mutex_lock(&markers_mutex);
 	entry = get_marker_from_private_data(probe, probe_private);
-	WARN_ON(!entry);
+	if (!entry)
+		goto end;
 	if (entry->rcu_pending)
 		rcu_barrier_sched();
 	entry->oldptr = old;

-- 
Mathieu Desnoyers
OpenPGP key fingerprint: 8CD5 52C3 8E3C 4140 715F  BA06 3F25 A8FE 3BAE 9A68
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