From: Ingo Molnar <mingo@elte.hu>
It adds cond_resched_softirq() which can be used by _process context_
softirqs-disabled codepaths to preempt if necessary. The function will
enable softirqs before scheduling. (Later patches will use this
primitive.)
Signed-off-by: Ingo Molnar <mingo@elte.hu>
Signed-off-by: Andrew Morton <akpm@osdl.org>
---
25-akpm/include/linux/sched.h | 3 +++
25-akpm/kernel/sched.c | 16 ++++++++++++++++
2 files changed, 19 insertions(+)
diff -puN include/linux/sched.h~sched-add-cond_resched_softirq include/linux/sched.h
--- 25/include/linux/sched.h~sched-add-cond_resched_softirq 2004-10-01 20:15:30.436563544 -0700
+++ 25-akpm/include/linux/sched.h 2004-10-01 20:15:30.442562632 -0700
@@ -1126,9 +1126,12 @@ static inline int need_resched(void)
* cond_resched() and cond_resched_lock(): latency reduction via
* explicit rescheduling in places that are safe. The return
* value indicates whether a reschedule was done in fact.
+ * cond_resched_lock() will drop the spinlock before scheduling,
+ * cond_resched_softirq() will enable bhs before scheduling.
*/
extern int cond_resched(void);
extern int cond_resched_lock(spinlock_t * lock);
+extern int cond_resched_softirq(void);
/*
* Does a critical section need to be broken due to another
diff -puN kernel/sched.c~sched-add-cond_resched_softirq kernel/sched.c
--- 25/kernel/sched.c~sched-add-cond_resched_softirq 2004-10-01 20:15:30.438563240 -0700
+++ 25-akpm/kernel/sched.c 2004-10-01 20:15:30.445562176 -0700
@@ -4131,6 +4131,22 @@ int cond_resched_lock(spinlock_t * lock)
EXPORT_SYMBOL(cond_resched_lock);
+int __sched cond_resched_softirq(void)
+{
+ BUG_ON(!in_softirq());
+
+ if (need_resched()) {
+ __local_bh_enable();
+ __cond_resched();
+ local_bh_disable();
+ return 1;
+ }
+ return 0;
+}
+
+EXPORT_SYMBOL(cond_resched_softirq);
+
+
/**
* yield - yield the current processor to other threads.
*
_