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authorTheodore Ts'o <tytso@mit.edu>2013-03-04 11:59:12 -0500
committerTheodore Ts'o <tytso@mit.edu>2013-03-04 12:05:15 -0500
commitb980955236922ae6106774511c5c05003d3ad225 (patch)
tree3eba34d4587e58ec7b15e8fb4af5572620288fe6 /drivers/char
parent19f949f52599ba7c3f67a5897ac6be14bfcb1200 (diff)
downloadop-kernel-dev-b980955236922ae6106774511c5c05003d3ad225.zip
op-kernel-dev-b980955236922ae6106774511c5c05003d3ad225.tar.gz
random: fix locking dependency with the tasklist_lock
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@mit.edu> Reported-by: Russ Dill <Russ.Dill@gmail.com> Cc: stable@kernel.org
Diffstat (limited to 'drivers/char')
-rw-r--r--drivers/char/random.c12
1 files changed, 8 insertions, 4 deletions
diff --git a/drivers/char/random.c b/drivers/char/random.c
index 85e81ec..57d4b15 100644
--- a/drivers/char/random.c
+++ b/drivers/char/random.c
@@ -852,6 +852,7 @@ 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);
@@ -873,10 +874,8 @@ 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 %zu entropy credits from %s%s\n",
@@ -884,6 +883,11 @@ 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;
}
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