Commit-ID: 35a773a07926a22bf19d77ee00024522279c4e68
Gitweb: http://git.kernel.org/tip/35a773a07926a22bf19d77ee00024522279c4e68
Author: Peter Zijlstra <peterz@xxxxxxxxxxxxx>
AuthorDate: Mon, 19 Sep 2016 12:57:53 +0200
Committer: Ingo Molnar <mingo@xxxxxxxxxx>
CommitDate: Thu, 22 Sep 2016 14:53:46 +0200
sched/core: Avoid _cond_resched() for PREEMPT=y
On fully preemptible kernels _cond_resched() is pointless, so avoid
emitting any code for it.
Signed-off-by: Peter Zijlstra (Intel) <peterz@xxxxxxxxxxxxx>
Cc: Linus Torvalds <torvalds@xxxxxxxxxxxxxxxxxxxx>
Cc: Mikulas Patocka <mpatocka@xxxxxxxxxx>
Cc: Oleg Nesterov <oleg@xxxxxxxxxx>
Cc: Peter Zijlstra <peterz@xxxxxxxxxxxxx>
Cc: Thomas Gleixner <tglx@xxxxxxxxxxxxx>
Cc: linux-kernel@xxxxxxxxxxxxxxx
Signed-off-by: Ingo Molnar <mingo@xxxxxxxxxx>
---
include/linux/sched.h | 4 ++++
kernel/sched/core.c | 2 ++
2 files changed, 6 insertions(+)
diff --git a/include/linux/sched.h b/include/linux/sched.h
index f00ee8e..b99fcd1 100644
--- a/include/linux/sched.h
+++ b/include/linux/sched.h
@@ -3209,7 +3209,11 @@ static inline int signal_pending_state(long state, struct task_struct *p)
* cond_resched_lock() will drop the spinlock before scheduling,
* cond_resched_softirq() will enable bhs before scheduling.
*/
+#ifndef CONFIG_PREEMPT
extern int _cond_resched(void);
+#else
+static inline int _cond_resched(void) { return 0; }
+#endif
#define cond_resched() ({ \
___might_sleep(__FILE__, __LINE__, 0); \
diff --git a/kernel/sched/core.c b/kernel/sched/core.c
index b2ec53c..d7babcc 100644
--- a/kernel/sched/core.c
+++ b/kernel/sched/core.c
@@ -4883,6 +4883,7 @@ SYSCALL_DEFINE0(sched_yield)
return 0;
}
+#ifndef CONFIG_PREEMPT
int __sched _cond_resched(void)
{
if (should_resched(0)) {
@@ -4892,6 +4893,7 @@ int __sched _cond_resched(void)
return 0;
}
EXPORT_SYMBOL(_cond_resched);
+#endif
/*
* __cond_resched_lock() - if a reschedule is pending, drop the given lock,
--
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