diff options
| author | Theodore Ts'o <tytso@mit.edu> | 2013-03-04 11:59:12 -0500 |
|---|---|---|
| committer | TARKZiM <tom8476oo@gmail.com> | 2022-08-25 20:05:39 +0800 |
| commit | 9e779e1e2861f523633e53c2faa2ceb58426d9e9 (patch) | |
| tree | 6900de7afa5d0f7b6a42a0391f50ca568a8b5dc3 | |
| parent | 9220c20fb11d1e6cf889a708fa47afbda50eab0f (diff) | |
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
| -rw-r--r-- | drivers/char/random.c | 12 |
1 files changed, 8 insertions, 4 deletions
diff --git a/drivers/char/random.c b/drivers/char/random.c index 12083d8c8ab..7fd08ea3467 100644 --- a/drivers/char/random.c +++ b/drivers/char/random.c @@ -871,6 +871,7 @@ 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); @@ -900,10 +901,8 @@ retry: goto retry; } - if (entropy_count < random_write_wakeup_thresh) { - wake_up_interruptible(&random_write_wait); - kill_fasync(&fasync, SIGIO, POLL_OUT); - } + if (entropy_count < random_write_wakeup_thresh) + wakeup_write = 1; } DEBUG_ENT("debiting %zu entropy credits from %s%s\n", @@ -911,6 +910,11 @@ retry: spin_unlock_irqrestore(&r->lock, flags); + if (wakeup_write) { + wake_up_interruptible(&random_write_wait); + kill_fasync(&fasync, SIGIO, POLL_OUT); + } + return nbytes; } |