From: Adrian Hunter <adrian.hunter@intel.com>
To: Can Guo <cang@codeaurora.org>
Cc: asutoshd@codeaurora.org, nguyenb@codeaurora.org,
hongwus@codeaurora.org, ziqichen@codeaurora.org,
linux-scsi@vger.kernel.org, kernel-team@android.com,
Alim Akhtar <alim.akhtar@samsung.com>,
Avri Altman <avri.altman@wdc.com>,
"James E.J. Bottomley" <jejb@linux.ibm.com>,
"Martin K. Petersen" <martin.petersen@oracle.com>,
Stanley Chu <stanley.chu@mediatek.com>,
Bean Huo <beanhuo@micron.com>, Jaegeuk Kim <jaegeuk@kernel.org>,
open list <linux-kernel@vger.kernel.org>
Subject: Re: [PATCH v4 06/10] scsi: ufs: Remove host_sem used in suspend/resume
Date: Thu, 24 Jun 2021 08:52:24 +0300 [thread overview]
Message-ID: <a87e5ca5-390f-8ca0-41bf-27cdc70e3316@intel.com> (raw)
In-Reply-To: <9105f328ee6ce916a7f01027b0d28332@codeaurora.org>
On 24/06/21 5:16 am, Can Guo wrote:
> 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.
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.
>
>>
>>> 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
>>>
next prev parent reply other threads:[~2021-06-24 5:52 UTC|newest]
Thread overview: 58+ messages / expand[flat|nested] mbox.gz Atom feed top
[not found] <1624433711-9339-1-git-send-email-cang@codeaurora.org>
2021-06-23 7:35 ` [PATCH v4 01/10] scsi: ufs: Rename flags pm_op_in_progress and is_sys_suspended Can Guo
2021-06-23 20:05 ` Bart Van Assche
2021-06-23 20:57 ` Bart Van Assche
2021-06-24 2:02 ` Can Guo
2021-06-24 2:34 ` Can Guo
2021-06-24 6:04 ` Adrian Hunter
2021-06-23 20:42 ` Bjorn Andersson
2021-06-23 22:41 ` Bart Van Assche
2021-06-24 2:04 ` Can Guo
2021-06-24 17:32 ` Bart Van Assche
2021-06-24 23:42 ` Bart Van Assche
2021-06-28 7:01 ` Can Guo
2021-06-28 7:35 ` Can Guo
2021-06-28 17:07 ` Bart Van Assche
2021-06-23 7:35 ` [PATCH v4 02/10] scsi: ufs: Add " Can Guo
2021-06-23 12:33 ` Adrian Hunter
2021-06-24 2:05 ` Can Guo
2021-06-23 20:59 ` Bart Van Assche
2021-06-24 2:07 ` Can Guo
2021-06-24 17:35 ` Bart Van Assche
2021-06-28 7:11 ` Can Guo
2021-06-23 7:35 ` [PATCH v4 03/10] scsi: ufs: Update the return value of supplier pm ops Can Guo
2021-06-23 21:08 ` Bart Van Assche
2021-06-24 2:11 ` Can Guo
2021-06-23 7:35 ` [PATCH v4 04/10] scsi: ufs: Enable IRQ after enabling clocks in error handling preparation Can Guo
2021-06-23 21:20 ` Bart Van Assche
2021-06-23 7:35 ` [PATCH 05/10] scsi: ufs: Complete the cmd before returning in queuecommand Can Guo
2021-06-23 7:39 ` Can Guo
2021-06-23 7:35 ` [PATCH v4 05/10] scsi: ufs: Remove a redundant tag check in ufshcd_queuecommand() Can Guo
2021-06-23 21:24 ` Bart Van Assche
2021-06-23 7:35 ` [PATCH v4 06/10] scsi: ufs: Remove host_sem used in suspend/resume Can Guo
2021-06-23 14:30 ` Adrian Hunter
2021-06-24 2:16 ` Can Guo
2021-06-24 5:52 ` Adrian Hunter [this message]
2021-06-24 6:12 ` Can Guo
2021-06-24 6:23 ` Adrian Hunter
2021-06-24 6:31 ` Can Guo
2021-06-24 10:04 ` Adrian Hunter
2021-06-28 7:26 ` Can Guo
2021-07-07 19:04 ` Adrian Hunter
2021-06-24 17:11 ` Bart Van Assche
2021-06-28 8:17 ` Can Guo
2021-06-28 17:31 ` Bart Van Assche
2021-06-29 6:23 ` Can Guo
2021-06-29 18:01 ` Bart Van Assche
2021-06-29 21:50 ` Can Guo
2021-06-23 7:35 ` [PATCH v4 07/10] scsi: ufs: Simplify error handling preparation Can Guo
2021-06-23 21:30 ` Bart Van Assche
2021-06-23 7:35 ` [PATCH v4 08/10] scsi: ufs: Update ufshcd_recover_pm_error() Can Guo
2021-06-23 7:35 ` [PATCH v4 09/10] scsi: ufs: Update the fast abort path in ufshcd_abort() for PM requests Can Guo
2021-06-23 21:33 ` Bart Van Assche
2021-06-24 4:16 ` Can Guo
2021-06-24 16:57 ` Bart Van Assche
2021-06-23 7:35 ` [PATCH v4 10/10] scsi: ufs: Apply more limitations to user access Can Guo
2021-06-23 21:51 ` Bart Van Assche
2021-06-24 2:23 ` Can Guo
2021-06-24 22:25 ` Bart Van Assche
2021-06-28 7:16 ` Can Guo
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