[PATCH v2 1/2] bus: mhi: ep: Fix potential deadlock in mhi_ep_reset_worker()

[Sumit Kumar]

There is a potential deadlock scenario in mhi_ep_reset_worker() where
the state_lock mutex is acquired twice in the same call chain:

mhi_ep_reset_worker()
  mutex_lock(&mhi_cntrl->state_lock)
    mhi_ep_power_up()
      mhi_ep_set_ready_state()
        mutex_lock(&mhi_cntrl->state_lock)  <- Deadlock

Fix this by releasing the state_lock before calling mhi_ep_power_up().
The lock is only needed to protect current MHI state read operation. The
lock can be safely released before proceeding with the power up sequence.

Fixes: 7a97b6b47353 ("bus: mhi: ep: Add support for handling MHI_RESET")
Signed-off-by: Sumit Kumar <sumit.kumar@xxxxxxxxxxxxxxxx>
---
 drivers/bus/mhi/ep/main.c | 7 +++----
 1 file changed, 3 insertions(+), 4 deletions(-)

diff --git a/drivers/bus/mhi/ep/main.c b/drivers/bus/mhi/ep/main.c
index cdea24e9291959ae0a92487c1b9698dc8164d2f1..4bb007d1933315e5b0b40d235248d5373548d3f4 100644
--- a/drivers/bus/mhi/ep/main.c
+++ b/drivers/bus/mhi/ep/main.c
@@ -1087,11 +1087,12 @@ static void mhi_ep_reset_worker(struct work_struct *work)
 
 	mhi_ep_power_down(mhi_cntrl);
 
-	mutex_lock(&mhi_cntrl->state_lock);
-
 	/* Reset MMIO to signal host that the MHI_RESET is completed in endpoint */
 	mhi_ep_mmio_reset(mhi_cntrl);
+
+	mutex_lock(&mhi_cntrl->state_lock);
 	cur_state = mhi_cntrl->mhi_state;
+	mutex_unlock(&mhi_cntrl->state_lock);
 
 	/*
 	 * Only proceed further if the reset is due to SYS_ERR. The host will
@@ -1100,8 +1101,6 @@ static void mhi_ep_reset_worker(struct work_struct *work)
 	 */
 	if (cur_state == MHI_STATE_SYS_ERR)
 		mhi_ep_power_up(mhi_cntrl);
-
-	mutex_unlock(&mhi_cntrl->state_lock);
 }
 
 /*

-- 
2.34.1