From 87dcbc0610cb580c8eaf289f52aca3620af825f0 Mon Sep 17 00:00:00 2001 From: Peter Zijlstra Date: Mon, 28 Sep 2015 17:45:40 +0200 Subject: [PATCH] sched/core: Simplify INIT_PREEMPT_COUNT As per the following commit: d86ee4809d03 ("sched: optimize cond_resched()") we need PREEMPT_ACTIVE to avoid cond_resched() from working before the scheduler is set up. However, keeping preemption disabled should do the same thing already, making the PREEMPT_ACTIVE part entirely redundant. The only complication is !PREEMPT_COUNT kernels, where PREEMPT_DISABLED ends up being 0. Instead we use an unconditional PREEMPT_OFFSET to set preempt_count() even on !PREEMPT_COUNT kernels. Signed-off-by: Peter Zijlstra (Intel) Reviewed-by: Steven Rostedt Reviewed-by: Thomas Gleixner Reviewed-by: Frederic Weisbecker Cc: Linus Torvalds Cc: Mike Galbraith Cc: Peter Zijlstra Cc: linux-kernel@vger.kernel.org Signed-off-by: Ingo Molnar --- include/linux/sched.h | 11 +++++------ 1 file changed, 5 insertions(+), 6 deletions(-) diff --git a/include/linux/sched.h b/include/linux/sched.h index d086cf0..e5b8cbc 100644 --- a/include/linux/sched.h +++ b/include/linux/sched.h @@ -606,19 +606,18 @@ struct task_cputime_atomic { #endif /* - * Disable preemption until the scheduler is running. - * Reset by start_kernel()->sched_init()->init_idle(). + * Disable preemption until the scheduler is running -- use an unconditional + * value so that it also works on !PREEMPT_COUNT kernels. * - * We include PREEMPT_ACTIVE to avoid cond_resched() from working - * before the scheduler is active -- see should_resched(). + * Reset by start_kernel()->sched_init()->init_idle()->init_idle_preempt_count(). */ -#define INIT_PREEMPT_COUNT (PREEMPT_DISABLED + PREEMPT_ACTIVE) +#define INIT_PREEMPT_COUNT PREEMPT_OFFSET /** * struct thread_group_cputimer - thread group interval timer counts * @cputime_atomic: atomic thread group interval timers. * @running: non-zero when there are timers running and - * @cputime receives updates. + * @cputime receives updates. * * This structure contains the version of task_cputime, above, that is * used for thread group CPU timer calculations. -- 2.7.4