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perf: perf_event_exit_task_context: s/rcu_dereference/rcu_dereference_raw/

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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>
This commit is contained in:
Oleg Nesterov 2011-01-21 18:45:47 +01:00 committed by Ingo Molnar
parent 547e9fd7d3
commit 806839b22c
1 changed files with 1 additions and 1 deletions
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2
kernel/perf_event.c
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@ -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);
/*