No released kernels are affected. It's purely a matter that has happened
after 2.6.25. The semaphore simplifcation in -rc1 caused a huge
performance regression on some benchmarks, and the fix to that in turn
caused a semaphore correctness issue, so I just rolled back to the
original BKL code that doesn't have any of those interactions.
In a historical context, the issues involved would only have happened with
CONFIG_PREEMPT_BKL. That config option was made the only one in January,
and as a result of these issues, we effectively switched it off.
So you can *think* of the effect of the changes as having gone from
CONFIG_PREEMPT_BKL=y to CONFIG_PREEMPT_BKL=n, even though technically we
had removed the actual config option to let people choose (so the config
option has basically become a static code change).
We may end up having to re-instate the config option due to this.
Personally, I hope not. It would be nicer if we could just avoid
PREEMPT_BKL entirely.
(To make things somewhat more confusing, some non-PREEMPT_BKL code has
then bitrotted since, so if can actually see latency issues, you might
want to try the patch here at the end of this email to see if it fixes
the worst of them. "cond_resched()" has regressed since the PREEMPT_BKL
config option went away).
Linus
---
include/linux/sched.h | 7 -------
1 files changed, 0 insertions(+), 7 deletions(-)
diff --git a/include/linux/sched.h b/include/linux/sched.h
index 5a63f2d..75c284f 100644
--- a/include/linux/sched.h
+++ b/include/linux/sched.h
@@ -2038,17 +2038,10 @@ static inline int need_resched(void)
* cond_resched_softirq() will enable bhs before scheduling.
*/
extern int _cond_resched(void);
-#ifdef CONFIG_PREEMPT
-static inline int cond_resched(void)
-{
- return 0;
-}
-#else
static inline int cond_resched(void)
{
return _cond_resched();
}
-#endif
extern int cond_resched_lock(spinlock_t * lock);
extern int cond_resched_softirq(void);
static inline int cond_resched_bkl(void)
--
