migrate_disable() does nothing !SMP && !RT. This is bad for two reasons: - The futex code relies on the fact migrate_disable() is part of spin_lock(). There is a workaround for the !in_atomic() case in migrate_disable() which work-arounds the different ordering (non-atomic lock and atomic unlock).
- we have a few instances where preempt_disable() is replaced with migrate_disable(). For both cases it is bad if migrate_disable() ends up as barrier() instead of preempt_disable(). Let migrate_disable() fallback to preempt_disable(). Cc: [email protected] Reported-by: [email protected] Signed-off-by: Sebastian Andrzej Siewior <[email protected]> --- include/linux/preempt.h | 4 ++-- kernel/sched/core.c | 2 ++ 2 files changed, 4 insertions(+), 2 deletions(-) diff --git a/include/linux/preempt.h b/include/linux/preempt.h index 043e431a7e8e..d46688d521e6 100644 --- a/include/linux/preempt.h +++ b/include/linux/preempt.h @@ -241,8 +241,8 @@ static inline int __migrate_disabled(struct task_struct *p) } #else -#define migrate_disable() barrier() -#define migrate_enable() barrier() +#define migrate_disable() preempt_disable() +#define migrate_enable() preempt_enable() static inline int __migrate_disabled(struct task_struct *p) { return 0; diff --git a/kernel/sched/core.c b/kernel/sched/core.c index ac3fb8495bd5..626a62218518 100644 --- a/kernel/sched/core.c +++ b/kernel/sched/core.c @@ -7326,6 +7326,7 @@ void migrate_disable(void) #endif p->migrate_disable++; + preempt_disable(); } EXPORT_SYMBOL(migrate_disable); @@ -7349,6 +7350,7 @@ void migrate_enable(void) WARN_ON_ONCE(p->migrate_disable <= 0); p->migrate_disable--; + preempt_enable(); } EXPORT_SYMBOL(migrate_enable); #endif -- 2.18.0
