From e37e112de3ac64032df45c2db0dbe1e8f1af86b4 Mon Sep 17 00:00:00 2001 From: Frederic Weisbecker Date: Fri, 7 Oct 2011 18:22:08 +0200 Subject: [PATCH] x86: Enter rcu extended qs after idle notifier call The idle notifier, called by enter_idle(), enters into rcu read side critical section but at that time we already switched into the RCU-idle window (rcu_idle_enter() has been called). And it's illegal to use rcu_read_lock() in that state. This results in rcu reporting its bad mood: [ 1.275635] WARNING: at include/linux/rcupdate.h:194 __atomic_notifier_call_chain+0xd2/0x110() [ 1.275635] Hardware name: AMD690VM-FMH [ 1.275635] Modules linked in: [ 1.275635] Pid: 0, comm: swapper Not tainted 3.0.0-rc6+ #252 [ 1.275635] Call Trace: [ 1.275635] [] warn_slowpath_common+0x7a/0xb0 [ 1.275635] [] warn_slowpath_null+0x15/0x20 [ 1.275635] [] __atomic_notifier_call_chain+0xd2/0x110 [ 1.275635] [] atomic_notifier_call_chain+0x11/0x20 [ 1.275635] [] enter_idle+0x20/0x30 [ 1.275635] [] cpu_idle+0xa5/0x110 [ 1.275635] [] rest_init+0xe5/0x140 [ 1.275635] [] ? rest_init+0x48/0x140 [ 1.275635] [] start_kernel+0x3d1/0x3dc [ 1.275635] [] x86_64_start_reservations+0x131/0x135 [ 1.275635] [] x86_64_start_kernel+0xed/0xf4 [ 1.275635] ---[ end trace a22d306b065d4a66 ]--- Fix this by entering rcu extended quiescent state later, just before the CPU goes to sleep. Signed-off-by: Frederic Weisbecker Cc: Paul E. McKenney Cc: Ingo Molnar Cc: Thomas Gleixner Cc: H. Peter Anvin Signed-off-by: Paul E. McKenney Reviewed-by: Josh Triplett --- arch/x86/kernel/process_64.c | 10 ++++++++-- 1 file changed, 8 insertions(+), 2 deletions(-) diff --git a/arch/x86/kernel/process_64.c b/arch/x86/kernel/process_64.c index 18e8cf3..64e926c 100644 --- a/arch/x86/kernel/process_64.c +++ b/arch/x86/kernel/process_64.c @@ -122,7 +122,7 @@ void cpu_idle(void) /* endless idle loop with no priority at all */ while (1) { - tick_nohz_idle_enter_norcu(); + tick_nohz_idle_enter(); while (!need_resched()) { rmb(); @@ -139,8 +139,14 @@ void cpu_idle(void) enter_idle(); /* Don't trace irqs off for idle */ stop_critical_timings(); + + /* enter_idle() needs rcu for notifiers */ + rcu_idle_enter(); + if (cpuidle_idle_call()) pm_idle(); + + rcu_idle_exit(); start_critical_timings(); /* In many cases the interrupt that ended idle @@ -149,7 +155,7 @@ void cpu_idle(void) __exit_idle(); } - tick_nohz_idle_exit_norcu(); + tick_nohz_idle_exit(); preempt_enable_no_resched(); schedule(); preempt_disable(); -- 2.7.4