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| author | Theodore Ts'o <tytso@mit.edu> | 2013-03-04 11:59:12 -0500 |
|---|---|---|
| committer | Theodore Ts'o <tytso@mit.edu> | 2013-03-04 12:05:15 -0500 |
| commit | b980955236922ae6106774511c5c05003d3ad225 (patch) | |
| tree | 3eba34d4587e58ec7b15e8fb4af5572620288fe6 /drivers/char | |
| parent | 19f949f52599ba7c3f67a5897ac6be14bfcb1200 (diff) | |
| download | linux-b980955236922ae6106774511c5c05003d3ad225.tar.gz linux-b980955236922ae6106774511c5c05003d3ad225.tar.bz2 linux-b980955236922ae6106774511c5c05003d3ad225.zip | |
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.c | 12 |
1 files changed, 8 insertions, 4 deletions
diff --git a/drivers/char/random.c b/drivers/char/random.c index 85e81ec1451e..57d4b152267c 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; } |