The following deadlocks have been observed on multiple test setups:
* ufshcd_wl_suspend() is waiting for blk_execute_rq() to complete while it
holds host_sem.
* ufshcd_eh_host_reset_handler() invokes ufshcd_err_handler() and the
latter function tries to obtain host_sem.
This is a deadlock because blk_execute_rq() can't execute SCSI commands
while the host is in the SHOST_RECOVERY state and because the error
handler cannot make progress either.
* ufshcd_wl_runtime_resume() is waiting for blk_execute_rq() to finish
while it holds host_sem.
* ufshcd_eh_host_reset_handler() invokes ufshcd_err_handler() and the
latter function calls pm_runtime_resume().
This is a deadlock because of the same reason as the previous scenario.
Fix both deadlocks by not obtaining host_sem from the power management
code paths. Removing the host_sem locking from the power management code
is safe because the ufshcd_err_handler() is already serialized against
SCSI command execution.
The ufshcd_rpm_get_sync() call at the start of
ufshcd_err_handling_prepare() may deadlock since calling scsi_execute()
is required by the UFS runtime resume implementation. Fixing that
deadlock falls outside the scope of this patch.
Cc: dh0421.hwang@xxxxxxxxxxx
Cc: Asutosh Das <asutoshd@xxxxxxxxxxxxxx>
Fixes: b294ff3e3449 ("scsi: ufs: core: Enable power management for wlun")
Signed-off-by: Bart Van Assche <bvanassche@xxxxxxx>
---
drivers/ufs/core/ufshcd.c | 6 +-----
1 file changed, 1 insertion(+), 5 deletions(-)
diff --git a/drivers/ufs/core/ufshcd.c b/drivers/ufs/core/ufshcd.c
index 7c15cbc737b4..cd3c2aa981c6 100644
--- a/drivers/ufs/core/ufshcd.c
+++ b/drivers/ufs/core/ufshcd.c
@@ -9254,16 +9254,13 @@ static int ufshcd_wl_suspend(struct device *dev)
ktime_t start = ktime_get();
hba = shost_priv(sdev->host);
- down(&hba->host_sem);
if (pm_runtime_suspended(dev))
goto out;
ret = __ufshcd_wl_suspend(hba, UFS_SYSTEM_PM);
- if (ret) {
+ if (ret)
dev_err(&sdev->sdev_gendev, "%s failed: %d\n", __func__, ret);
- up(&hba->host_sem);
- }
out:
if (!ret)
@@ -9296,7 +9293,6 @@ static int ufshcd_wl_resume(struct device *dev)
hba->curr_dev_pwr_mode, hba->uic_link_state);
if (!ret)
hba->is_sys_suspended = false;
- up(&hba->host_sem);
return ret;
}
#endif
