[PATCH v2 0/2] bus: mhi: ep: Fix state_lock protection issues

[PATCH v2 0/2] bus: mhi: ep: Fix state_lock protection issues

[Sumit Kumar]

This series fixes a deadlock in mhi_ep_reset_worker() where state_lock is
acquired twice, and adds missing lock protection for mhi_state access in
mhi_ep_power_up() to prevent race conditions and state machine corruption.

Signed-off-by: Sumit Kumar <sumit.kumar@oss.qualcomm.com>
---
Changes in v2:
- Move `mhi_ep_mmio_reset()` out of state mutex lock.(Mani).
- Removed the mutex lock from `mhi_ep_handle_syserr()`, since the caller of
  mhi_ep_handle_syserr() holds the lock.(Mani)
- Link to v1: https://lore.kernel.org/r/20260203-reset_worker_deadlock-v1-0-7ed889b5bf19@oss.qualcomm.com

---
Sumit Kumar (2):
      bus: mhi: ep: Fix potential deadlock in mhi_ep_reset_worker()
      bus: mhi: ep: Add missing state_lock protection for mhi_state access

 drivers/bus/mhi/ep/main.c | 9 +++++----
 1 file changed, 5 insertions(+), 4 deletions(-)
---
base-commit: 6fa9041b7177f6771817b95e83f6df17b147c8c6
change-id: 20251113-reset_worker_deadlock-0223907f7c9d

Best regards,
-- 
Sumit Kumar <sumit.kumar@oss.qualcomm.com>

[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@oss.qualcomm.com>
---
 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

[PATCH v2 2/2] bus: mhi: ep: Add missing state_lock protection for mhi_state access

[Sumit Kumar]

The mhi_cntrl->mhi_state field should be protected by state_lock to
ensure atomic state transitions. However, mhi_ep_power_up() access
mhi_state without holding this lock, which can race with concurrent state
transitions and lead to state corruption.

Add proper state_lock protection around mhi_state access.

Fixes: fb3a26b7e8af ("bus: mhi: ep: Add support for powering up the MHI endpoint stack")
Fixes: f7d0806bdb1b3 ("bus: mhi: ep: Add support for handling SYS_ERR condition")
Signed-off-by: Sumit Kumar <sumit.kumar@oss.qualcomm.com>
---
 drivers/bus/mhi/ep/main.c | 2 ++
 1 file changed, 2 insertions(+)

diff --git a/drivers/bus/mhi/ep/main.c b/drivers/bus/mhi/ep/main.c
index 4bb007d1933315e5b0b40d235248d5373548d3f4..eefb0a6c82f68bf95f5c7418afa595c47519dee5 100644
--- a/drivers/bus/mhi/ep/main.c
+++ b/drivers/bus/mhi/ep/main.c
@@ -1148,7 +1148,9 @@ int mhi_ep_power_up(struct mhi_ep_cntrl *mhi_cntrl)
 	for (i = 0; i < mhi_cntrl->event_rings; i++)
 		mhi_ep_ring_init(&mhi_cntrl->mhi_event[i].ring, RING_TYPE_ER, i);
 
+	mutex_lock(&mhi_cntrl->state_lock);
 	mhi_cntrl->mhi_state = MHI_STATE_RESET;
+	mutex_unlock(&mhi_cntrl->state_lock);
 
 	/* Set AMSS EE before signaling ready state */
 	mhi_ep_mmio_set_env(mhi_cntrl, MHI_EE_AMSS);

-- 
2.34.1

Re: [PATCH v2 0/2] bus: mhi: ep: Fix state_lock protection issues

[Manivannan Sadhasivam]

On Tue, 14 Apr 2026 11:59:39 +0530, Sumit Kumar wrote:
> This series fixes a deadlock in mhi_ep_reset_worker() where state_lock is
> acquired twice, and adds missing lock protection for mhi_state access in
> mhi_ep_power_up() to prevent race conditions and state machine corruption.

Applied, thanks!

[1/2] bus: mhi: ep: Fix potential deadlock in mhi_ep_reset_worker()
      commit: 9dece4435d396e9877e27483552b910ba8654169
[2/2] bus: mhi: ep: Add missing state_lock protection for mhi_state access
      commit: ce3e534ee9c8d13a68c8a611c3b7bd0c2152d2ab

Best regards,
-- 
Manivannan Sadhasivam <manivannan.sadhasivam@oss.qualcomm.com>