This is a note to let you know that I've just added the patch titled
random: fix locking dependency with the tasklist_lock
to the 3.8-stable tree which can be found at:
http://www.kernel.org/git/?p=linux/kernel/git/stable/stable-queue.git;a=summary
The filename of the patch is:
random-fix-locking-dependency-with-the-tasklist_lock.patch
and it can be found in the queue-3.8 subdirectory.
If you, or anyone else, feels it should not be added to the stable tree,
please let <[email protected]> know about it.
>From b980955236922ae6106774511c5c05003d3ad225 Mon Sep 17 00:00:00 2001
From: Theodore Ts'o <[email protected]>
Date: Mon, 4 Mar 2013 11:59:12 -0500
Subject: random: fix locking dependency with the tasklist_lock
From: Theodore Ts'o <[email protected]>
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" <[email protected]>
Reported-by: Russ Dill <[email protected]>
Signed-off-by: Greg Kroah-Hartman <[email protected]>
---
drivers/char/random.c | 12 ++++++++----
1 file changed, 8 insertions(+), 4 deletions(-)
--- a/drivers/char/random.c
+++ b/drivers/char/random.c
@@ -852,6 +852,7 @@ static size_t account(struct entropy_sto
int reserved)
{
unsigned long flags;
+ int wakeup_write = 0;
/* Hold lock while accounting */
spin_lock_irqsave(&r->lock, flags);
@@ -873,10 +874,8 @@ static size_t account(struct entropy_sto
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 %zu entropy credits from %s%s\n",
@@ -884,6 +883,11 @@ static size_t account(struct entropy_sto
spin_unlock_irqrestore(&r->lock, flags);
+ if (wakeup_write) {
+ wake_up_interruptible(&random_write_wait);
+ kill_fasync(&fasync, SIGIO, POLL_OUT);
+ }
+
return nbytes;
}
Patches currently in stable-queue which might be from [email protected] are
queue-3.8/random-fix-locking-dependency-with-the-tasklist_lock.patch
queue-3.8/ext4-convert-number-of-blocks-to-clusters-properly.patch
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