[PATCH] scsi: core: ufs: Fix a hang in the error handler

[Bart Van Assche <bvanassche@acm.org>]

From: Sanjeev Yadav <sanjeev.y@mediatek.com>

ufshcd_err_handling_prepare() calls ufshcd_rpm_get_sync(). The latter
function can only succeed if UFSHCD_EH_IN_PROGRESS is not set because
resuming involves submitting a SCSI command and ufshcd_queuecommand()
returns SCSI_MLQUEUE_HOST_BUSY if UFSHCD_EH_IN_PROGRESS is set. Fix
this hang by setting UFSHCD_EH_IN_PROGRESS after
ufshcd_rpm_get_sync() has been called instead of before.

Backtrace:
__switch_to+0x174/0x338
__schedule+0x600/0x9e4
schedule+0x7c/0xe8
schedule_timeout+0xa4/0x1c8
io_schedule_timeout+0x48/0x70
wait_for_common_io+0xa8/0x160 //waiting on START_STOP
wait_for_completion_io_timeout+0x10/0x20
blk_execute_rq+0xe4/0x1e4
scsi_execute_cmd+0x108/0x244
ufshcd_set_dev_pwr_mode+0xe8/0x250
__ufshcd_wl_resume+0x94/0x354
ufshcd_wl_runtime_resume+0x3c/0x174
scsi_runtime_resume+0x64/0xa4
rpm_resume+0x15c/0xa1c
__pm_runtime_resume+0x4c/0x90 // Runtime resume ongoing
ufshcd_err_handler+0x1a0/0xd08
process_one_work+0x174/0x808
worker_thread+0x15c/0x490
kthread+0xf4/0x1ec
ret_from_fork+0x10/0x20

Signed-off-by: Sanjeev Yadav <sanjeev.y@mediatek.com>
[ bvanassche: rewrote patch description ]
Fixes: 62694735ca95 ("[SCSI] ufs: Add runtime PM support for UFS host controller driver")
Signed-off-by: Bart Van Assche <bvanassche@acm.org>
---
 drivers/ufs/core/ufshcd.c | 7 ++++++-
 1 file changed, 6 insertions(+), 1 deletion(-)

diff --git a/drivers/ufs/core/ufshcd.c b/drivers/ufs/core/ufshcd.c
index 34a499b19480..b43dd1f88fbc 100644
--- a/drivers/ufs/core/ufshcd.c
+++ b/drivers/ufs/core/ufshcd.c
@@ -6530,9 +6530,14 @@ static void ufshcd_err_handler(struct ufs_hba *hba)
 		up(&hba->host_sem);
 		return;
 	}
-	ufshcd_set_eh_in_progress(hba);
 	spin_unlock_irqrestore(hba->host->host_lock, flags);
+
 	ufshcd_err_handling_prepare(hba);
+
+	spin_lock_irqsave(hba->host->host_lock, flags);
+	ufshcd_set_eh_in_progress(hba);
+	spin_unlock_irqrestore(hba->host->host_lock, flags);
+
 	/* Complete requests that have door-bell cleared by h/w */
 	ufshcd_complete_requests(hba, false);
 	spin_lock_irqsave(hba->host->host_lock, flags);