On Mon, Mar 4, 2013 at 9:05 AM, Theodore Ts'o <ty...@mit.edu> wrote: > Russ, how about this patch instead? Can you verify whether or not > this fixes your issue? If so, I'll push it to Linus. > > - Ted
Yup, fixes the circular locking dependency. Tested-by: russ.d...@gmail.com > From 24c598b5abd466f2bab954d0cc8c225e0d3a2a74 Mon Sep 17 00:00:00 2001 > From: Theodore Ts'o <ty...@mit.edu> > Date: Mon, 4 Mar 2013 11:59:12 -0500 > Subject: [PATCH] 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" <ty...@mit.edu> > Reported-by: Russ Dill <russ.d...@gmail.com> > Cc: sta...@kernel.org > --- > 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 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; > } > > -- > 1.7.12.rc0.22.gcdd159b > -- To unsubscribe from this list: send the line "unsubscribe linux-kernel" in the body of a message to majord...@vger.kernel.org More majordomo info at http://vger.kernel.org/majordomo-info.html Please read the FAQ at http://www.tux.org/lkml/