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SubjectRe: [PATCH v4 06/10] scsi: ufs: Remove host_sem used in suspend/resume
On 2021-06-23 22:30, Adrian Hunter wrote:
> On 23/06/21 10:35 am, Can Guo wrote:
>> 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 <cang@codeaurora.org>
>> ---
>> 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.

Thanks,

Can Guo.

>
>> 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
>>

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