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authorOleg Nesterov <oleg@redhat.com>2011-01-21 18:45:47 +0100
committerIngo Molnar <mingo@elte.hu>2011-01-21 22:08:16 +0100
commit806839b22cbda90176d7f8d421889bddd7826e93 (patch)
tree3ee967f97fa5e29ada85fb1d60142c75503e0ffd
parent547e9fd7d328af261f184bf66effc5033c886498 (diff)
downloadop-kernel-dev-806839b22cbda90176d7f8d421889bddd7826e93.zip
op-kernel-dev-806839b22cbda90176d7f8d421889bddd7826e93.tar.gz
perf: perf_event_exit_task_context: s/rcu_dereference/rcu_dereference_raw/
In theory, almost every user of task->child->perf_event_ctxp[] is wrong. find_get_context() can install the new context at any moment, we need read_barrier_depends(). dbe08d82ce3967ccdf459f7951d02589cf967300 "perf: Fix find_get_context() vs perf_event_exit_task() race" added rcu_dereference() into perf_event_exit_task_context() to make the precedent, but this makes __rcu_dereference_check() unhappy. Use rcu_dereference_raw() to shut up the warning. Reported-by: Ingo Molnar <mingo@elte.hu> Signed-off-by: Oleg Nesterov <oleg@redhat.com> Cc: acme@redhat.com Cc: paulus@samba.org Cc: stern@rowland.harvard.edu Cc: a.p.zijlstra@chello.nl Cc: fweisbec@gmail.com Cc: roland@redhat.com Cc: prasad@linux.vnet.ibm.com Cc: Paul E. McKenney <paulmck@linux.vnet.ibm.com> LKML-Reference: <20110121174547.GA8796@redhat.com> Signed-off-by: Ingo Molnar <mingo@elte.hu>
-rw-r--r--kernel/perf_event.c2
1 files changed, 1 insertions, 1 deletions
diff --git a/kernel/perf_event.c b/kernel/perf_event.c
index c5fa717..126a302 100644
--- a/kernel/perf_event.c
+++ b/kernel/perf_event.c
@@ -6136,7 +6136,7 @@ static void perf_event_exit_task_context(struct task_struct *child, int ctxn)
* scheduled, so we are now safe from rescheduling changing
* our context.
*/
- child_ctx = rcu_dereference(child->perf_event_ctxp[ctxn]);
+ child_ctx = rcu_dereference_raw(child->perf_event_ctxp[ctxn]);
task_ctx_sched_out(child_ctx, EVENT_ALL);
/*
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