[PATCH] lockdep: fix delayacct locking bug

Make the delayacct lock irqsave; this avoids the possible deadlock where
an interrupt is taken while holding the delayacct lock which needs to
take the delayacct lock.

Signed-off-by: Peter Zijlstra <a.p.zijlstra@chello.nl>
Acked-by: Oleg Nesterov <oleg@tv-sign.ru>
Cc: Balbir Singh <balbir@in.ibm.com>
Cc: Shailabh Nagar <nagar@watson.ibm.com>
Signed-off-by: Andrew Morton <akpm@osdl.org>
Signed-off-by: Linus Torvalds <torvalds@osdl.org>

1 files changed, 9 insertions, 6 deletions

diff --git a/kernel/delayacct.c b/kernel/delayacct.c
index 36752f124c6a..66a0ea48751d 100644
--- a/kernel/delayacct.c
+++ b/kernel/delayacct.c
@@ -66,6 +66,7 @@ static void delayacct_end(struct timespec *start, struct timespec *end,
 {
         struct timespec ts;
         s64 ns;
+        unsigned long flags;
 
         do_posix_clock_monotonic_gettime(end);
         ts = timespec_sub(*end, *start);
@@ -73,10 +74,10 @@ static void delayacct_end(struct timespec *start, struct timespec *end,
         if (ns < 0)
                 return;
 
-        spin_lock(&current->delays->lock);
+        spin_lock_irqsave(&current->delays->lock, flags);
         *total += ns;
         (*count)++;
-        spin_unlock(&current->delays->lock);
+        spin_unlock_irqrestore(&current->delays->lock, flags);
 }
 
 void __delayacct_blkio_start(void)
@@ -104,6 +105,7 @@ int __delayacct_add_tsk(struct taskstats *d, struct task_struct *tsk)
         s64 tmp;
         struct timespec ts;
         unsigned long t1,t2,t3;
+        unsigned long flags;
 
         /* Though tsk->delays accessed later, early exit avoids
          * unnecessary returning of other data
@@ -136,14 +138,14 @@ int __delayacct_add_tsk(struct taskstats *d, struct task_struct *tsk)
 
         /* zero XXX_total, non-zero XXX_count implies XXX stat overflowed */
 
-        spin_lock(&tsk->delays->lock);
+        spin_lock_irqsave(&tsk->delays->lock, flags);
         tmp = d->blkio_delay_total + tsk->delays->blkio_delay;
         d->blkio_delay_total = (tmp < d->blkio_delay_total) ? 0 : tmp;
         tmp = d->swapin_delay_total + tsk->delays->swapin_delay;
         d->swapin_delay_total = (tmp < d->swapin_delay_total) ? 0 : tmp;
         d->blkio_count += tsk->delays->blkio_count;
         d->swapin_count += tsk->delays->swapin_count;
-        spin_unlock(&tsk->delays->lock);
+        spin_unlock_irqrestore(&tsk->delays->lock, flags);
 
 done:
         return 0;
@@ -152,11 +154,12 @@ done:
 __u64 __delayacct_blkio_ticks(struct task_struct *tsk)
 {
         __u64 ret;
+        unsigned long flags;
 
-        spin_lock(&tsk->delays->lock);
+        spin_lock_irqsave(&tsk->delays->lock, flags);
         ret = nsec_to_clock_t(tsk->delays->blkio_delay +
                                 tsk->delays->swapin_delay);
-        spin_unlock(&tsk->delays->lock);
+        spin_unlock_irqrestore(&tsk->delays->lock, flags);
         return ret;
 }