From a093b93ee0e08cd73a07848752bc09ecea68cb13 Mon Sep 17 00:00:00 2001 From: Li Zhong Date: Fri, 23 Nov 2012 00:05:03 +0100 Subject: cpuidle: fix a suspicious RCU usage in menu governor I saw this suspicious RCU usage on the next tree of 11/15 [ 67.123404] =============================== [ 67.123413] [ INFO: suspicious RCU usage. ] [ 67.123423] 3.7.0-rc5-next-20121115-dirty #1 Not tainted [ 67.123434] ------------------------------- [ 67.123444] include/trace/events/timer.h:186 suspicious rcu_dereference_check() usage! [ 67.123458] [ 67.123458] other info that might help us debug this: [ 67.123458] [ 67.123474] [ 67.123474] RCU used illegally from idle CPU! [ 67.123474] rcu_scheduler_active = 1, debug_locks = 0 [ 67.123493] RCU used illegally from extended quiescent state! [ 67.123507] 1 lock held by swapper/1/0: [ 67.123516] #0: (&cpu_base->lock){-.-...}, at: [] .__hrtimer_start_range_ns+0x28c/0x524 [ 67.123555] [ 67.123555] stack backtrace: [ 67.123566] Call Trace: [ 67.123576] [c0000001e2ccb920] [c00000000001275c] .show_stack+0x78/0x184 (unreliable) [ 67.123599] [c0000001e2ccb9d0] [c0000000000c15a0] .lockdep_rcu_suspicious+0x120/0x148 [ 67.123619] [c0000001e2ccba70] [c00000000009601c] .enqueue_hrtimer+0x1c0/0x1c8 [ 67.123639] [c0000001e2ccbb00] [c000000000097aa0] .__hrtimer_start_range_ns+0x37c/0x524 [ 67.123660] [c0000001e2ccbc20] [c0000000005c9698] .menu_select+0x508/0x5bc [ 67.123678] [c0000001e2ccbd20] [c0000000005c740c] .cpuidle_idle_call+0xa8/0x6e4 [ 67.123699] [c0000001e2ccbdd0] [c0000000000459a0] .pSeries_idle+0x10/0x34 [ 67.123717] [c0000001e2ccbe40] [c000000000014dc8] .cpu_idle+0x130/0x280 [ 67.123738] [c0000001e2ccbee0] [c0000000006ffa8c] .start_secondary+0x378/0x384 [ 67.123758] [c0000001e2ccbf90] [c00000000000936c] .start_secondary_prolog+0x10/0x14 hrtimer_start was added in 198fd638 and ae515197. The patch below tries to use RCU_NONIDLE around it to avoid the above report. Signed-off-by: Li Zhong Acked-by: Paul E. McKenney Reviewed-by: Rik van Riel Signed-off-by: Rafael J. Wysocki --- drivers/cpuidle/governors/menu.c | 10 ++++++---- 1 file changed, 6 insertions(+), 4 deletions(-) diff --git a/drivers/cpuidle/governors/menu.c b/drivers/cpuidle/governors/menu.c index 2efee27714a..bd40b943b6d 100644 --- a/drivers/cpuidle/governors/menu.c +++ b/drivers/cpuidle/governors/menu.c @@ -407,8 +407,9 @@ static int menu_select(struct cpuidle_driver *drv, struct cpuidle_device *dev) perfect_us = perfect_cstate_ms * 1000; if (repeat && (4 * timer_us < data->expected_us)) { - hrtimer_start(hrtmr, ns_to_ktime(1000 * timer_us), - HRTIMER_MODE_REL_PINNED); + RCU_NONIDLE(hrtimer_start(hrtmr, + ns_to_ktime(1000 * timer_us), + HRTIMER_MODE_REL_PINNED)); /* In repeat case, menu hrtimer is started */ per_cpu(hrtimer_status, cpu) = MENU_HRTIMER_REPEAT; } else if (perfect_us < data->expected_us) { @@ -418,8 +419,9 @@ static int menu_select(struct cpuidle_driver *drv, struct cpuidle_device *dev) * In that case, it makes sense to re-enter * into a deeper C-state after some time. */ - hrtimer_start(hrtmr, ns_to_ktime(1000 * timer_us), - HRTIMER_MODE_REL_PINNED); + RCU_NONIDLE(hrtimer_start(hrtmr, + ns_to_ktime(1000 * timer_us), + HRTIMER_MODE_REL_PINNED)); /* In general case, menu hrtimer is started */ per_cpu(hrtimer_status, cpu) = MENU_HRTIMER_GENERAL; } -- cgit v1.2.3