sched: Add a preempt count base offset to __might_sleep()

Add a preempt count base offset to compare against the current
preempt level count. It prepares to pull up the might_sleep
check from cond_resched() to cond_resched_lock() and
cond_resched_bh().

For these two helpers, we need to respectively ensure that once
we'll unlock the given spinlock / reenable local softirqs, we
will reach a sleepable state.

Signed-off-by: Frederic Weisbecker <fweisbec@gmail.com>
[ Move and rename preempt_count_equals() ]
Signed-off-by: Peter Zijlstra <a.p.zijlstra@chello.nl>
LKML-Reference: <1247725694-6082-4-git-send-email-fweisbec@gmail.com>
Signed-off-by: Ingo Molnar <mingo@elte.hu>

1 files changed, 11 insertions, 4 deletions

diff --git a/kernel/sched.c b/kernel/sched.c
index 370a6c31c5e..3ff4d004bd9 100644
--- a/kernel/sched.c
+++ b/kernel/sched.c
@@ -6610,7 +6610,7 @@ static inline int should_resched(void)
 
 static void __cond_resched(void)
 {
-        __might_sleep(__FILE__, __LINE__);
+        __might_sleep(__FILE__, __LINE__, 0);
 
         add_preempt_count(PREEMPT_ACTIVE);
         schedule();
@@ -9429,13 +9429,20 @@ void __init sched_init(void)
 }
 
 #ifdef CONFIG_DEBUG_SPINLOCK_SLEEP
-void __might_sleep(char *file, int line)
+static inline int preempt_count_equals(int preempt_offset)
+{
+        int nested = preempt_count() & ~PREEMPT_ACTIVE;
+
+        return (nested == PREEMPT_INATOMIC_BASE + preempt_offset);
+}
+
+void __might_sleep(char *file, int line, int preempt_offset)
 {
 #ifdef in_atomic
         static unsigned long prev_jiffy;        /* ratelimiting */
 
-        if ((!in_atomic() && !irqs_disabled()) ||
-                    system_state != SYSTEM_RUNNING || oops_in_progress)
+        if ((preempt_count_equals(preempt_offset) && !irqs_disabled()) ||
+            system_state != SYSTEM_RUNNING || oops_in_progress)
                 return;
         if (time_before(jiffies, prev_jiffy + HZ) && prev_jiffy)
                 return;