Commit-ID: 87dcbc0610cb580c8eaf289f52aca3620af825f0
Gitweb: http://git.kernel.org/tip/87dcbc0610cb580c8eaf289f52aca3620af825f0
Author: Peter Zijlstra <peterz@xxxxxxxxxxxxx>
AuthorDate: Mon, 28 Sep 2015 17:45:40 +0200
Committer: Ingo Molnar <mingo@xxxxxxxxxx>
CommitDate: Tue, 6 Oct 2015 17:08:12 +0200
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) <peterz@xxxxxxxxxxxxx>
Reviewed-by: Steven Rostedt <rostedt@xxxxxxxxxxx>
Reviewed-by: Thomas Gleixner <tglx@xxxxxxxxxxxxx>
Reviewed-by: Frederic Weisbecker <fweisbec@xxxxxxxxx>
Cc: Linus Torvalds <torvalds@xxxxxxxxxxxxxxxxxxxx>
Cc: Mike Galbraith <efault@xxxxxx>
Cc: Peter Zijlstra <peterz@xxxxxxxxxxxxx>
Cc: linux-kernel@xxxxxxxxxxxxxxx
Signed-off-by: Ingo Molnar <mingo@xxxxxxxxxx>
---
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.
--
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