3.5.7.8 -stable review patch. If anyone has any objections, please let me know.
------------------
From: Theodore Ts'o <tytso@xxxxxxx>
commit b980955236922ae6106774511c5c05003d3ad225 upstream.
Commit 6133705494bb introduced a circular lock dependency because
posix_cpu_timers_exit() is called by release_task(), which is holding
a writer lock on tasklist_lock, and this can cause a deadlock since
kill_fasync() gets called with nonblocking_pool.lock taken.
There's no reason why kill_fasync() needs to be taken while the random
pool is locked, so move it out to fix this locking dependency.
Signed-off-by: "Theodore Ts'o" <tytso@xxxxxxx>
Reported-by: Russ Dill <Russ.Dill@xxxxxxxxx>
Signed-off-by: Luis Henriques <luis.henriques@xxxxxxxxxxxxx>
---
drivers/char/random.c | 12 ++++++++----
1 file changed, 8 insertions(+), 4 deletions(-)
diff --git a/drivers/char/random.c b/drivers/char/random.c
index d98b2a6..91abbc4 100644
--- a/drivers/char/random.c
+++ b/drivers/char/random.c
@@ -855,6 +855,7 @@ static size_t account(struct entropy_store *r, size_t nbytes, int min,
int reserved)
{
unsigned long flags;
+ int wakeup_write = 0;
/* Hold lock while accounting */
spin_lock_irqsave(&r->lock, flags);
@@ -876,10 +877,8 @@ static size_t account(struct entropy_store *r, size_t nbytes, int min,
else
r->entropy_count = reserved;
- if (r->entropy_count < random_write_wakeup_thresh) {
- wake_up_interruptible(&random_write_wait);
- kill_fasync(&fasync, SIGIO, POLL_OUT);
- }
+ if (r->entropy_count < random_write_wakeup_thresh)
+ wakeup_write = 1;
}
DEBUG_ENT("debiting %d entropy credits from %s%s\n",
@@ -887,6 +886,11 @@ static size_t account(struct entropy_store *r, size_t nbytes, int min,
spin_unlock_irqrestore(&r->lock, flags);
+ if (wakeup_write) {
+ wake_up_interruptible(&random_write_wait);
+ kill_fasync(&fasync, SIGIO, POLL_OUT);
+ }
+
return nbytes;
}
--
1.8.1.2
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