From mboxrd@z Thu Jan 1 00:00:00 1970 From: Peter Hurley Subject: [PATCH v5 27/44] tty: Drop lock contention stat from ldsem trylocks Date: Mon, 11 Mar 2013 16:44:47 -0400 Message-ID: <1363034704-28036-28-git-send-email-peter@hurleysoftware.com> References: <1361390599-15195-1-git-send-email-peter@hurleysoftware.com> <1363034704-28036-1-git-send-email-peter@hurleysoftware.com> Return-path: In-Reply-To: <1363034704-28036-1-git-send-email-peter@hurleysoftware.com> Sender: linux-kernel-owner@vger.kernel.org To: Greg Kroah-Hartman , Jiri Slaby Cc: Sasha Levin , Dave Jones , Sebastian Andrzej Siewior , Shawn Guo , linux-kernel@vger.kernel.org, linux-serial@vger.kernel.org, Peter Hurley List-Id: linux-serial@vger.kernel.org When lockdep is notified of lock contention, lockdep expects its internal state to indicate the lock is held. Since trylocks cannot reflect this state unless the lock is actually acquired, contention stats cannot be collected for trylocks. Fixes: [ 1473.912280] ================================= [ 1473.913180] [ BUG: bad contention detected! ] [ 1473.914071] 3.8.0-next-20130220-sasha-00038-g1ad55df-dirty #8 Tainted: G W [ 1473.915684] --------------------------------- [ 1473.916549] kworker/1:1/361 is trying to contend lock (&tty->ldisc_sem) at: [ 1473.918031] [] tty_ldisc_ref+0x1f/0x60 [ 1473.919060] but there are no locks held! [ 1473.919813] [ 1473.919813] other info that might help us debug this: [ 1473.920044] 2 locks held by kworker/1:1/361: [ 1473.920044] #0: (events){.+.+.+}, at: [] process_one_work+0x228/0x6a0 [ 1473.920044] #1: ((&buf->work)){+.+...}, at: [] process_one_work+0x228/0x6a0 [ 1473.920044] [ 1473.920044] stack backtrace: [ 1473.920044] Pid: 361, comm: kworker/1:1 Tainted: G W 3.8.0-next-20130220-sasha-00038-g1ad55df-dirty #8 [ 1473.920044] Call Trace: [ 1473.920044] [] ? tty_ldisc_ref+0x1f/0x60 [ 1473.920044] [] print_lock_contention_bug+0xf6/0x110 [ 1473.920044] [] lock_contended+0x213/0x4e0 [ 1473.920044] [] ldsem_down_read_trylock+0xb1/0xc0 [ 1473.920044] [] tty_ldisc_ref+0x1f/0x60 [ 1473.920044] [] flush_to_ldisc+0x37/0x1a0 [ 1473.920044] [] process_one_work+0x366/0x6a0 [ 1473.920044] [] ? process_one_work+0x228/0x6a0 [ 1473.920044] [] worker_thread+0x238/0x370 [ 1473.920044] [] ? rescuer_thread+0x310/0x310 [ 1473.920044] [] kthread+0xe3/0xf0 [ 1473.920044] [] ? flush_kthread_work+0x1f0/0x1f0 [ 1473.920044] [] ret_from_fork+0x7c/0xb0 [ 1473.920044] [] ? flush_kthread_work+0x1f0/0x1f0 Reported-by: Sasha Levin Signed-off-by: Peter Hurley --- drivers/tty/tty_ldsem.c | 3 --- 1 file changed, 3 deletions(-) diff --git a/drivers/tty/tty_ldsem.c b/drivers/tty/tty_ldsem.c index 0ab5b09..c162295 100644 --- a/drivers/tty/tty_ldsem.c +++ b/drivers/tty/tty_ldsem.c @@ -419,7 +419,6 @@ int ldsem_down_read_trylock(struct ld_semaphore *sem) return 1; } } - lock_stat(sem, contended); return 0; } @@ -453,9 +452,7 @@ int ldsem_down_write_trylock(struct ld_semaphore *sem) lock_stat(sem, acquired); return 1; } - raw_spin_unlock_irq(&sem->wait_lock); - lock_stat(sem, contended); return 0; } -- 1.8.1.2