PREEMPT_ACTIVE implies non-preemptible context and thus atomic context despite what in_atomic*() APIs reports about it. These functions shouldn't ignore this value like they are currently doing.
It appears that these APIs were ignoring PREEMPT_ACTIVE in order to ease the check in schedule_debug(). Meanwhile it is sufficient to rely on PREEMPT_ACTIVE in order to disable preemption in __schedule(). So lets fix the in_atomic*() APIs and simplify the preempt count ops on __schedule() callers. Suggested-by: Linus Torvalds <[email protected]> Cc: Ingo Molnar <[email protected]> Cc: Steven Rostedt <[email protected]> Cc: Linus Torvalds <[email protected]> Cc: Peter Zijlstra <[email protected]> Signed-off-by: Frederic Weisbecker <[email protected]> --- include/linux/preempt_mask.h | 4 ++-- kernel/sched/core.c | 12 ++++++------ 2 files changed, 8 insertions(+), 8 deletions(-) diff --git a/include/linux/preempt_mask.h b/include/linux/preempt_mask.h index dbeec4d..4b8c9b7 100644 --- a/include/linux/preempt_mask.h +++ b/include/linux/preempt_mask.h @@ -99,14 +99,14 @@ * used in the general case to determine whether sleeping is possible. * Do not use in_atomic() in driver code. */ -#define in_atomic() ((preempt_count() & ~PREEMPT_ACTIVE) != 0) +#define in_atomic() (preempt_count() != 0) /* * Check whether we were atomic before we did preempt_disable(): * (used by the scheduler, *after* releasing the kernel lock) */ #define in_atomic_preempt_off() \ - ((preempt_count() & ~PREEMPT_ACTIVE) != PREEMPT_CHECK_OFFSET) + (preempt_count() & ~(PREEMPT_ACTIVE | PREEMPT_CHECK_OFFSET)) #ifdef CONFIG_PREEMPT_COUNT # define preemptible() (preempt_count() == 0 && !irqs_disabled()) diff --git a/kernel/sched/core.c b/kernel/sched/core.c index 1c0e5b1..c017a5f 100644 --- a/kernel/sched/core.c +++ b/kernel/sched/core.c @@ -2882,9 +2882,9 @@ void __sched schedule_preempt_disabled(void) static void preempt_schedule_common(void) { do { - preempt_count_add(PREEMPT_ACTIVE + PREEMPT_CHECK_OFFSET); + preempt_count_add(PREEMPT_ACTIVE); __schedule(); - preempt_count_sub(PREEMPT_ACTIVE + PREEMPT_CHECK_OFFSET); + preempt_count_sub(PREEMPT_ACTIVE); /* * Check again in case we missed a preemption opportunity @@ -2937,7 +2937,7 @@ asmlinkage __visible void __sched notrace preempt_schedule_context(void) return; do { - preempt_count_add(PREEMPT_ACTIVE + PREEMPT_CHECK_OFFSET); + preempt_count_add(PREEMPT_ACTIVE); /* * Needs preempt disabled in case user_exit() is traced * and the tracer calls preempt_enable_notrace() causing @@ -2946,7 +2946,7 @@ asmlinkage __visible void __sched notrace preempt_schedule_context(void) prev_ctx = exception_enter(); __schedule(); exception_exit(prev_ctx); - preempt_count_sub(PREEMPT_ACTIVE + PREEMPT_CHECK_OFFSET); + preempt_count_sub(PREEMPT_ACTIVE); barrier(); } while (need_resched()); } @@ -2971,11 +2971,11 @@ asmlinkage __visible void __sched preempt_schedule_irq(void) prev_state = exception_enter(); do { - preempt_count_add(PREEMPT_ACTIVE + PREEMPT_CHECK_OFFSET); + preempt_count_add(PREEMPT_ACTIVE); local_irq_enable(); __schedule(); local_irq_disable(); - preempt_count_sub(PREEMPT_ACTIVE + PREEMPT_CHECK_OFFSET); + preempt_count_sub(PREEMPT_ACTIVE); /* * Check again in case we missed a preemption opportunity -- 2.1.4 -- To unsubscribe from this list: send the line "unsubscribe linux-kernel" in the body of a message to [email protected] More majordomo info at http://vger.kernel.org/majordomo-info.html Please read the FAQ at http://www.tux.org/lkml/
