On 24/06/21 5:16 am, Can Guo wrote:

On 2021-06-23 22:30, Adrian Hunter wrote:

quoted

On 23/06/21 10:35 am, Can Guo wrote:

quoted

To protect system suspend/resume from being disturbed by error handling,
instead of using host_sem, let error handler call lock_system_sleep() and
unlock_system_sleep() which achieve the same purpose. Remove the host_sem
used in suspend/resume paths to make the code more readable.

Suggested-by: Bart Van Assche <bvanassche@acm.org>
Signed-off-by: Can Guo <redacted>
---
 drivers/scsi/ufs/ufshcd.c | 12 +++++++-----
 1 file changed, 7 insertions(+), 5 deletions(-)

diff --git a/drivers/scsi/ufs/ufshcd.c b/drivers/scsi/ufs/ufshcd.c
index 3695dd2..a09e4a2 100644
--- a/drivers/scsi/ufs/ufshcd.c
+++ b/drivers/scsi/ufs/ufshcd.c

@@ -5907,6 +5907,11 @@ static void ufshcd_clk_scaling_suspend(struct ufs_hba *hba, bool suspend)

 static void ufshcd_err_handling_prepare(struct ufs_hba *hba)
 {
+    /*
+     * It is not safe to perform error handling while suspend or resume is
+     * in progress. Hence the lock_system_sleep() call.
+     */
+    lock_system_sleep();

It looks to me like the system takes this lock quite early, even before
freezing tasks, so if anything needs the error handler to run it will
deadlock.

Hi Adrian,

UFS/hba system suspend/resume does not invoke or call error handling in a
synchronous way. So, whatever UFS errors (which schedules the error handler)
happens during suspend/resume, error handler will just wait here till system
suspend/resume release the lock. Hence no worries of deadlock here.

It looks to me like the state can change to UFSHCD_STATE_EH_SCHEDULED_FATAL
and since user processes are not frozen, nor file systems sync'ed, everything
is going to deadlock.
i.e.
I/O is blocked waiting on error handling
error handling is blocked waiting on lock_system_sleep()
suspend is blocked waiting on I/O

Thanks,

Can Guo.

quoted

quoted

     ufshcd_rpm_get_sync(hba);
     if (pm_runtime_status_suspended(&hba->sdev_ufs_device->sdev_gendev) ||
         hba->is_wlu_sys_suspended) {

@@ -5951,6 +5956,7 @@ static void ufshcd_err_handling_unprepare(struct ufs_hba *hba)

         ufshcd_clk_scaling_suspend(hba, false);
     ufshcd_clear_ua_wluns(hba);
     ufshcd_rpm_put(hba);
+    unlock_system_sleep();
 }

 static inline bool ufshcd_err_handling_should_stop(struct ufs_hba *hba)

@@ -9053,16 +9059,13 @@ 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)

@@ -9095,7 +9098,6 @@ static int ufshcd_wl_resume(struct device *dev)

         hba->curr_dev_pwr_mode, hba->uic_link_state);
     if (!ret)
         hba->is_wlu_sys_suspended = false;
-    up(&hba->host_sem);
     return ret;
 }
 #endif