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markers: fix unregister 

Impact: fix marker registers/unregister race

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.

Signed-off-by: Mathieu Desnoyers <mathieu.desnoyers@polymtl.ca>
Signed-off-by: Ingo Molnar <mingo@elte.hu>
This commit is contained in:
Mathieu Desnoyers 2008-11-14 17:47:35 -05:00 committed by Ingo Molnar
parent 954e100d22
commit 2bdba316c9
1 changed files with 7 additions and 5 deletions
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12
kernel/marker.c
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@ -653,10 +653,11 @@ int marker_probe_register(const char *name, const char *format,
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 *name,
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(marker_probe_func *probe,
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;