From 8cb75e0c4ec9786b81439761eac1d18d4a931af3 Mon Sep 17 00:00:00 2001 From: Peter Zijlstra Date: Wed, 20 Nov 2013 12:22:37 +0100 Subject: sched/preempt: Fix up missed PREEMPT_NEED_RESCHED folding With various drivers wanting to inject idle time; we get people calling idle routines outside of the idle loop proper. Therefore we need to be extra careful about not missing TIF_NEED_RESCHED -> PREEMPT_NEED_RESCHED propagations. While looking at this, I also realized there's a small window in the existing idle loop where we can miss TIF_NEED_RESCHED; when it hits right after the tif_need_resched() test at the end of the loop but right before the need_resched() test at the start of the loop. So move preempt_fold_need_resched() out of the loop where we're guaranteed to have TIF_NEED_RESCHED set. Signed-off-by: Peter Zijlstra Link: http://lkml.kernel.org/n/tip-x9jgh45oeayzajz2mjt0y7d6@git.kernel.org Signed-off-by: Ingo Molnar --- include/linux/preempt.h | 15 +++++++++++++++ include/linux/sched.h | 15 +++++++++++++++ 2 files changed, 30 insertions(+) (limited to 'include') diff --git a/include/linux/preempt.h b/include/linux/preempt.h index dd9ddf8af205..59749fc48328 100644 --- a/include/linux/preempt.h +++ b/include/linux/preempt.h @@ -134,6 +134,21 @@ do { \ #undef preempt_check_resched #endif +#ifdef CONFIG_PREEMPT +#define preempt_set_need_resched() \ +do { \ + set_preempt_need_resched(); \ +} while (0) +#define preempt_fold_need_resched() \ +do { \ + if (tif_need_resched()) \ + set_preempt_need_resched(); \ +} while (0) +#else +#define preempt_set_need_resched() do { } while (0) +#define preempt_fold_need_resched() do { } while (0) +#endif + #ifdef CONFIG_PREEMPT_NOTIFIERS struct preempt_notifier; diff --git a/include/linux/sched.h b/include/linux/sched.h index a03875221663..ffccdad050b5 100644 --- a/include/linux/sched.h +++ b/include/linux/sched.h @@ -2745,6 +2745,21 @@ static inline bool __must_check current_clr_polling_and_test(void) } #endif +static inline void current_clr_polling(void) +{ + __current_clr_polling(); + + /* + * Ensure we check TIF_NEED_RESCHED after we clear the polling bit. + * Once the bit is cleared, we'll get IPIs with every new + * TIF_NEED_RESCHED and the IPI handler, scheduler_ipi(), will also + * fold. + */ + smp_mb(); /* paired with resched_task() */ + + preempt_fold_need_resched(); +} + static __always_inline bool need_resched(void) { return unlikely(tif_need_resched()); -- cgit v1.2.3