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Date: Mon, 29 Apr 2013 23:17:09 -0400 From: kosaki.motohiro@...il.com To: linux-kernel@...r.kernel.org Cc: Olivier Langlois <olivier@...llion01.com>, Martin Schwidefsky <schwidefsky@...ibm.com>, Steven Rostedt <rostedt@...dmis.org>, David Miller <davem@...emloft.net>, Thomas Gleixner <tglx@...utronix.de>, Frederic Weisbecker <fweisbec@...il.com>, Ingo Molnar <mingo@...nel.org>, Peter Zijlstra <peterz@...radead.org>, "Paul E. McKenney" <paulmck@...ux.vnet.ibm.com>, a.p.zijlstra@...llo.nl, paulus@...ba.org, acme@...stprotocols.net Subject: [PATCH 01/10] events: Protect access via task_subsys_state_check() From: Paul E. McKenney <paulmck@...ux.vnet.ibm.com> The following RCU splat indicates lack of RCU protection: [ 953.267649] =============================== [ 953.267652] [ INFO: suspicious RCU usage. ] [ 953.267657] 3.9.0-0.rc6.git2.4.fc19.ppc64p7 #1 Not tainted [ 953.267661] ------------------------------- [ 953.267664] include/linux/cgroup.h:534 suspicious rcu_dereference_check() usage! [ 953.267669] [ 953.267669] other info that might help us debug this: [ 953.267669] [ 953.267675] [ 953.267675] rcu_scheduler_active = 1, debug_locks = 0 [ 953.267680] 1 lock held by glxgears/1289: [ 953.267683] #0: (&sig->cred_guard_mutex){+.+.+.}, at: [<c00000000027f884>] .prepare_bprm_creds+0x34/0xa0 [ 953.267700] [ 953.267700] stack backtrace: [ 953.267704] Call Trace: [ 953.267709] [c0000001f0d1b6e0] [c000000000016e30] .show_stack+0x130/0x200 (unreliable) [ 953.267717] [c0000001f0d1b7b0] [c0000000001267f8] .lockdep_rcu_suspicious+0x138/0x180 [ 953.267724] [c0000001f0d1b840] [c0000000001d43a4] .perf_event_comm+0x4c4/0x690 [ 953.267731] [c0000001f0d1b950] [c00000000027f6e4] .set_task_comm+0x84/0x1f0 [ 953.267737] [c0000001f0d1b9f0] [c000000000280414] .setup_new_exec+0x94/0x220 [ 953.267744] [c0000001f0d1ba70] [c0000000002f665c] .load_elf_binary+0x58c/0x19b0 ... This commit therefore adds the required RCU read-side critical section to perf_event_comm(). Reported-by: Adam Jackson <ajax@...hat.com> Signed-off-by: Paul E. McKenney <paulmck@...ux.vnet.ibm.com> Cc: a.p.zijlstra@...llo.nl Cc: paulus@...ba.org Cc: acme@...stprotocols.net Link: http://lkml.kernel.org/r/20130419190124.GA8638@linux.vnet.ibm.com Signed-off-by: Ingo Molnar <mingo@...nel.org> Tested-by: Gustavo Luiz Duarte <gusld@...ibm.com> --- kernel/events/core.c | 2 ++ 1 files changed, 2 insertions(+), 0 deletions(-) diff --git a/kernel/events/core.c b/kernel/events/core.c index 4d3124b..9fcb094 100644 --- a/kernel/events/core.c +++ b/kernel/events/core.c @@ -4596,6 +4596,7 @@ void perf_event_comm(struct task_struct *task) struct perf_event_context *ctx; int ctxn; + rcu_read_lock(); for_each_task_context_nr(ctxn) { ctx = task->perf_event_ctxp[ctxn]; if (!ctx) @@ -4603,6 +4604,7 @@ void perf_event_comm(struct task_struct *task) perf_event_enable_on_exec(ctx); } + rcu_read_unlock(); if (!atomic_read(&nr_comm_events)) return; -- 1.7.1 -- To unsubscribe from this list: send the line "unsubscribe linux-kernel" in the body of a message to majordomo@...r.kernel.org More majordomo info at http://vger.kernel.org/majordomo-info.html Please read the FAQ at http://www.tux.org/lkml/
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