From: Oleg Nesterov Date: Fri, 21 Jan 2011 17:45:47 +0000 (+0100) Subject: perf: perf_event_exit_task_context: s/rcu_dereference/rcu_dereference_raw/ X-Git-Tag: v2.6.38-rc3~68^2~7 X-Git-Url: http://review.tizen.org/git/?a=commitdiff_plain;h=806839b22cbda90176d7f8d421889bddd7826e93;p=profile%2Fivi%2Fkernel-x86-ivi.git 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 Signed-off-by: Oleg Nesterov 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 LKML-Reference: <20110121174547.GA8796@redhat.com> Signed-off-by: Ingo Molnar --- diff --git a/kernel/perf_event.c b/kernel/perf_event.c index c5fa717cf09..126a302c481 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); /*