[RESEND PATCH] [SCSI] mpt2sas: fix double mutex lock in NON_BLOCKING state

If state is NON_BLOCKING and mutex_trylock is succeed,
the control flow goes to mutex_lock_interruptible() that is a deadlock.

Found by Linux Driver Verification project (linuxtesting.org).

Acked-by: "Nandigama, Nagalakshmi" <Nagalakshmi.Nandigama <at> lsi.com>
Signed-off-by: Alexey Khoroshilov <khoroshilov <at> ispras.ru>
---
 drivers/scsi/mpt2sas/mpt2sas_ctl.c |    6 ++++--
 1 file changed, 4 insertions(+), 2 deletions(-)

diff --git a/drivers/scsi/mpt2sas/mpt2sas_ctl.c b/drivers/scsi/mpt2sas/mpt2sas_ctl.c
index 49bdd2d..d29ea56 100644
--- a/drivers/scsi/mpt2sas/mpt2sas_ctl.c
+++ b/drivers/scsi/mpt2sas/mpt2sas_ctl.c
 <at>  <at>  -2181,8 +2181,10  <at>  <at>  _ctl_ioctl_main(struct file *file, unsigned int cmd, void __user *arg,
 		return -EAGAIN;

 	state = (file->f_flags & O_NONBLOCK) ? NON_BLOCKING : BLOCKING;
-	if (state == NON_BLOCKING && !mutex_trylock(&ioc->ctl_cmds.mutex))
-		return -EAGAIN;
+	if (state == NON_BLOCKING) {
+		if (!mutex_trylock(&ioc->ctl_cmds.mutex))
+			return -EAGAIN;
+	}
 	else if (mutex_lock_interruptible(&ioc->ctl_cmds.mutex))
 		return -ERESTARTSYS;

--

-- 
1.7.9.5