linux-kernel - [PATCH 1/2] bus: mhi: ep: Fix potential deadlock in mhi_ep_reset

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Message-Id: <20260203-reset_worker_deadlock-v1-1-7ed889b5bf19@oss.qualcomm.com>
Date: Tue, 03 Feb 2026 12:25:01 +0530
From: Sumit Kumar <sumit.kumar@....qualcomm.com>
To: Manivannan Sadhasivam <mani@...nel.org>, Alex Elder <elder@...nel.org>,
        Greg Kroah-Hartman <gregkh@...uxfoundation.org>
Cc: mhi@...ts.linux.dev, linux-arm-msm@...r.kernel.org,
        linux-kernel@...r.kernel.org,
        Veerabhadrarao Badiganti <veerabhadrarao.badiganti@....qualcomm.com>,
        Subramanian Ananthanarayanan <subramanian.ananthanarayanan@....qualcomm.com>,
        Akhil Vinod <akhil.vinod@....qualcomm.com>,
        Sumit Kumar <sumit.kumar@....qualcomm.com>
Subject: [PATCH 1/2] bus: mhi: ep: Fix potential deadlock in
 mhi_ep_reset_worker()

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@....qualcomm.com>
---
 drivers/bus/mhi/ep/main.c | 3 +--
 1 file changed, 1 insertion(+), 2 deletions(-)

diff --git a/drivers/bus/mhi/ep/main.c b/drivers/bus/mhi/ep/main.c
index cdea24e9291959ae0a92487c1b9698dc8164d2f1..73597de373ef7e0c428bcbc126d63a9a97f95144 100644
--- a/drivers/bus/mhi/ep/main.c
+++ b/drivers/bus/mhi/ep/main.c
@@ -1093,6 +1093,7 @@ static void mhi_ep_reset_worker(struct work_struct *work)
 	mhi_ep_mmio_reset(mhi_cntrl);
 	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
 	 * issue reset during shutdown also and we don't need to do re-init in
@@ -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