Add new 'cond_resched_bkl()' helper function

It acts exactly like a regular 'cond_resched()', but will not get
optimized away when CONFIG_PREEMPT is set.

Normal kernel code is already preemptable in the presense of
CONFIG_PREEMPT, so cond_resched() is optimized away (see commit
02b67cc3ba36bdba351d6c3a00593f4ec550d9d3 "sched: do not do
cond_resched() when CONFIG_PREEMPT").

But when wanting to conditionally reschedule while holding a lock, you
need to use "cond_sched_lock(lock)", and the new function is the BKL
equivalent of that.

Also make fs/locks.c use it.

Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>

1 files changed, 0 insertions, 2 deletions

diff --git a/kernel/sched.c b/kernel/sched.c
index c51b6565e07c..8841a915545d 100644
--- a/kernel/sched.c
+++ b/kernel/sched.c
@@ -5525,7 +5525,6 @@ static void __cond_resched(void)
         } while (need_resched());
 }
 
-#if !defined(CONFIG_PREEMPT) || defined(CONFIG_PREEMPT_VOLUNTARY)
 int __sched _cond_resched(void)
 {
         if (need_resched() && !(preempt_count() & PREEMPT_ACTIVE) &&
@@ -5536,7 +5535,6 @@ int __sched _cond_resched(void)
         return 0;
 }
 EXPORT_SYMBOL(_cond_resched);
-#endif
 
 /*
  * cond_resched_lock() - if a reschedule is pending, drop the given lock,