* Re: [PATCH v6] scsi: ufs: Quiesce all scsi devices before shutdown
@ 2020-08-03 5:03 ` Can Guo
0 siblings, 0 replies; 9+ messages in thread
From: Can Guo @ 2020-08-03 5:03 UTC (permalink / raw)
To: Stanley Chu
Cc: jiajie.hao, linux-scsi, martin.petersen, andy.teng, jejb,
chun-hung.wu, kuohong.wang, linux-kernel, asutoshd, avri.altman,
linux-mediatek, peter.wang, alim.akhtar, matthias.bgg, beanhuo,
chaotian.jing, cc.chou, linux-arm-kernel, bvanassche
Hi Stanley,
On 2020-08-03 12:25, Stanley Chu wrote:
> Currently I/O request could be still submitted to UFS device while
> UFS is working on shutdown flow. This may lead to racing as below
> scenarios and finally system may crash due to unclocked register
> accesses.
>
> To fix this kind of issues, in ufshcd_shutdown(),
>
> 1. Use pm_runtime_get_sync() instead of resuming UFS device by
> ufshcd_runtime_resume() "internally" to let runtime PM framework
> manage and prevent concurrent runtime operations by incoming I/O
> requests.
>
> 2. Specifically quiesce all SCSI devices to block all I/O requests
> after device is resumed.
>
> Example of racing scenario: While UFS device is runtime-suspended
>
> Thread #1: Executing UFS shutdown flow, e.g.,
> ufshcd_suspend(UFS_SHUTDOWN_PM)
>
> Thread #2: Executing runtime resume flow triggered by I/O request,
> e.g., ufshcd_resume(UFS_RUNTIME_PM)
>
> This breaks the assumption that UFS PM flows can not be running
> concurrently and some unexpected racing behavior may happen.
>
> Signed-off-by: Stanley Chu <stanley.chu@mediatek.com>
> ---
> Changes:
> - Since v4: Use pm_runtime_get_sync() instead of resuming UFS device
> by ufshcd_runtime_resume() "internally".
> ---
> drivers/scsi/ufs/ufshcd.c | 39 ++++++++++++++++++++++++++++++++++-----
> 1 file changed, 34 insertions(+), 5 deletions(-)
>
> diff --git a/drivers/scsi/ufs/ufshcd.c b/drivers/scsi/ufs/ufshcd.c
> index 307622284239..fc01171d13b1 100644
> --- a/drivers/scsi/ufs/ufshcd.c
> +++ b/drivers/scsi/ufs/ufshcd.c
> @@ -159,6 +159,12 @@ struct ufs_pm_lvl_states ufs_pm_lvl_states[] = {
> {UFS_POWERDOWN_PWR_MODE, UIC_LINK_OFF_STATE},
> };
>
> +#define ufshcd_scsi_for_each_sdev(fn) \
> + list_for_each_entry(starget, &hba->host->__targets, siblings) { \
> + __starget_for_each_device(starget, NULL, \
> + fn); \
> + }
> +
> static inline enum ufs_dev_pwr_mode
> ufs_get_pm_lvl_to_dev_pwr_mode(enum ufs_pm_level lvl)
> {
> @@ -8629,6 +8635,13 @@ int ufshcd_runtime_idle(struct ufs_hba *hba)
> }
> EXPORT_SYMBOL(ufshcd_runtime_idle);
>
> +static void ufshcd_quiesce_sdev(struct scsi_device *sdev, void *data)
> +{
> + /* Suspended devices are already quiesced so can be skipped */
Why can runtime suspended sdevs be skipped? Block layer can still resume
them at any time, no?
> + if (!pm_runtime_suspended(&sdev->sdev_gendev))
> + scsi_device_quiesce(sdev);
> +}
> +
> /**
> * ufshcd_shutdown - shutdown routine
> * @hba: per adapter instance
> @@ -8640,6 +8653,7 @@ EXPORT_SYMBOL(ufshcd_runtime_idle);
> int ufshcd_shutdown(struct ufs_hba *hba)
> {
> int ret = 0;
> + struct scsi_target *starget;
>
> if (!hba->is_powered)
> goto out;
> @@ -8647,11 +8661,26 @@ int ufshcd_shutdown(struct ufs_hba *hba)
> if (ufshcd_is_ufs_dev_poweroff(hba) && ufshcd_is_link_off(hba))
> goto out;
>
> - if (pm_runtime_suspended(hba->dev)) {
> - ret = ufshcd_runtime_resume(hba);
> - if (ret)
> - goto out;
> - }
> + /*
> + * Let runtime PM framework manage and prevent concurrent runtime
> + * operations with shutdown flow.
> + */
> + pm_runtime_get_sync(hba->dev);
> +
> + /*
> + * Quiesce all SCSI devices to prevent any non-PM requests sending
> + * from block layer during and after shutdown.
> + *
> + * Here we can not use blk_cleanup_queue() since PM requests
> + * (with BLK_MQ_REQ_PREEMPT flag) are still required to be sent
> + * through block layer. Therefore SCSI command queued after the
> + * scsi_target_quiesce() call returned will block until
> + * blk_cleanup_queue() is called.
> + *
> + * Besides, scsi_target_"un"quiesce (e.g., scsi_target_resume) can
> + * be ignored since shutdown is one-way flow.
> + */
> + ufshcd_scsi_for_each_sdev(ufshcd_quiesce_sdev);
Any reasons why don't use scsi_target_quiesce() here?
Thanks,
Can Guo.
>
> ret = ufshcd_suspend(hba, UFS_SHUTDOWN_PM);
> out:
_______________________________________________
linux-arm-kernel mailing list
linux-arm-kernel@lists.infradead.org
http://lists.infradead.org/mailman/listinfo/linux-arm-kernel
^ permalink raw reply [flat|nested] 9+ messages in thread* Re: [PATCH v6] scsi: ufs: Quiesce all scsi devices before shutdown
@ 2020-08-03 5:03 ` Can Guo
0 siblings, 0 replies; 9+ messages in thread
From: Can Guo @ 2020-08-03 5:03 UTC (permalink / raw)
To: Stanley Chu
Cc: linux-scsi, martin.petersen, avri.altman, alim.akhtar, jejb,
bvanassche, beanhuo, asutoshd, matthias.bgg, linux-mediatek,
linux-arm-kernel, linux-kernel, kuohong.wang, peter.wang,
chun-hung.wu, andy.teng, chaotian.jing, cc.chou, jiajie.hao
Hi Stanley,
On 2020-08-03 12:25, Stanley Chu wrote:
> Currently I/O request could be still submitted to UFS device while
> UFS is working on shutdown flow. This may lead to racing as below
> scenarios and finally system may crash due to unclocked register
> accesses.
>
> To fix this kind of issues, in ufshcd_shutdown(),
>
> 1. Use pm_runtime_get_sync() instead of resuming UFS device by
> ufshcd_runtime_resume() "internally" to let runtime PM framework
> manage and prevent concurrent runtime operations by incoming I/O
> requests.
>
> 2. Specifically quiesce all SCSI devices to block all I/O requests
> after device is resumed.
>
> Example of racing scenario: While UFS device is runtime-suspended
>
> Thread #1: Executing UFS shutdown flow, e.g.,
> ufshcd_suspend(UFS_SHUTDOWN_PM)
>
> Thread #2: Executing runtime resume flow triggered by I/O request,
> e.g., ufshcd_resume(UFS_RUNTIME_PM)
>
> This breaks the assumption that UFS PM flows can not be running
> concurrently and some unexpected racing behavior may happen.
>
> Signed-off-by: Stanley Chu <stanley.chu@mediatek.com>
> ---
> Changes:
> - Since v4: Use pm_runtime_get_sync() instead of resuming UFS device
> by ufshcd_runtime_resume() "internally".
> ---
> drivers/scsi/ufs/ufshcd.c | 39 ++++++++++++++++++++++++++++++++++-----
> 1 file changed, 34 insertions(+), 5 deletions(-)
>
> diff --git a/drivers/scsi/ufs/ufshcd.c b/drivers/scsi/ufs/ufshcd.c
> index 307622284239..fc01171d13b1 100644
> --- a/drivers/scsi/ufs/ufshcd.c
> +++ b/drivers/scsi/ufs/ufshcd.c
> @@ -159,6 +159,12 @@ struct ufs_pm_lvl_states ufs_pm_lvl_states[] = {
> {UFS_POWERDOWN_PWR_MODE, UIC_LINK_OFF_STATE},
> };
>
> +#define ufshcd_scsi_for_each_sdev(fn) \
> + list_for_each_entry(starget, &hba->host->__targets, siblings) { \
> + __starget_for_each_device(starget, NULL, \
> + fn); \
> + }
> +
> static inline enum ufs_dev_pwr_mode
> ufs_get_pm_lvl_to_dev_pwr_mode(enum ufs_pm_level lvl)
> {
> @@ -8629,6 +8635,13 @@ int ufshcd_runtime_idle(struct ufs_hba *hba)
> }
> EXPORT_SYMBOL(ufshcd_runtime_idle);
>
> +static void ufshcd_quiesce_sdev(struct scsi_device *sdev, void *data)
> +{
> + /* Suspended devices are already quiesced so can be skipped */
Why can runtime suspended sdevs be skipped? Block layer can still resume
them at any time, no?
> + if (!pm_runtime_suspended(&sdev->sdev_gendev))
> + scsi_device_quiesce(sdev);
> +}
> +
> /**
> * ufshcd_shutdown - shutdown routine
> * @hba: per adapter instance
> @@ -8640,6 +8653,7 @@ EXPORT_SYMBOL(ufshcd_runtime_idle);
> int ufshcd_shutdown(struct ufs_hba *hba)
> {
> int ret = 0;
> + struct scsi_target *starget;
>
> if (!hba->is_powered)
> goto out;
> @@ -8647,11 +8661,26 @@ int ufshcd_shutdown(struct ufs_hba *hba)
> if (ufshcd_is_ufs_dev_poweroff(hba) && ufshcd_is_link_off(hba))
> goto out;
>
> - if (pm_runtime_suspended(hba->dev)) {
> - ret = ufshcd_runtime_resume(hba);
> - if (ret)
> - goto out;
> - }
> + /*
> + * Let runtime PM framework manage and prevent concurrent runtime
> + * operations with shutdown flow.
> + */
> + pm_runtime_get_sync(hba->dev);
> +
> + /*
> + * Quiesce all SCSI devices to prevent any non-PM requests sending
> + * from block layer during and after shutdown.
> + *
> + * Here we can not use blk_cleanup_queue() since PM requests
> + * (with BLK_MQ_REQ_PREEMPT flag) are still required to be sent
> + * through block layer. Therefore SCSI command queued after the
> + * scsi_target_quiesce() call returned will block until
> + * blk_cleanup_queue() is called.
> + *
> + * Besides, scsi_target_"un"quiesce (e.g., scsi_target_resume) can
> + * be ignored since shutdown is one-way flow.
> + */
> + ufshcd_scsi_for_each_sdev(ufshcd_quiesce_sdev);
Any reasons why don't use scsi_target_quiesce() here?
Thanks,
Can Guo.
>
> ret = ufshcd_suspend(hba, UFS_SHUTDOWN_PM);
> out:
^ permalink raw reply [flat|nested] 9+ messages in thread* Re: [PATCH v6] scsi: ufs: Quiesce all scsi devices before shutdown
2020-08-03 5:03 ` Can Guo
(?)
@ 2020-08-03 9:58 ` Stanley Chu
-1 siblings, 0 replies; 9+ messages in thread
From: Stanley Chu @ 2020-08-03 9:58 UTC (permalink / raw)
To: Can Guo
Cc: jiajie.hao, linux-scsi, martin.petersen, andy.teng, jejb,
chun-hung.wu, kuohong.wang, linux-kernel, asutoshd, avri.altman,
linux-mediatek, peter.wang, alim.akhtar, matthias.bgg, beanhuo,
chaotian.jing, cc.chou, linux-arm-kernel, bvanassche
Hi Can,
On Mon, 2020-08-03 at 13:03 +0800, Can Guo wrote:
> Hi Stanley,
>
> On 2020-08-03 12:25, Stanley Chu wrote:
> > Currently I/O request could be still submitted to UFS device while
> > UFS is working on shutdown flow. This may lead to racing as below
> > scenarios and finally system may crash due to unclocked register
> > accesses.
> >
> > To fix this kind of issues, in ufshcd_shutdown(),
> >
> > 1. Use pm_runtime_get_sync() instead of resuming UFS device by
> > ufshcd_runtime_resume() "internally" to let runtime PM framework
> > manage and prevent concurrent runtime operations by incoming I/O
> > requests.
> >
> > 2. Specifically quiesce all SCSI devices to block all I/O requests
> > after device is resumed.
> >
> > Example of racing scenario: While UFS device is runtime-suspended
> >
> > Thread #1: Executing UFS shutdown flow, e.g.,
> > ufshcd_suspend(UFS_SHUTDOWN_PM)
> >
> > Thread #2: Executing runtime resume flow triggered by I/O request,
> > e.g., ufshcd_resume(UFS_RUNTIME_PM)
> >
> > This breaks the assumption that UFS PM flows can not be running
> > concurrently and some unexpected racing behavior may happen.
> >
> > Signed-off-by: Stanley Chu <stanley.chu@mediatek.com>
> > ---
> > Changes:
> > - Since v4: Use pm_runtime_get_sync() instead of resuming UFS device
> > by ufshcd_runtime_resume() "internally".
> > ---
> > drivers/scsi/ufs/ufshcd.c | 39 ++++++++++++++++++++++++++++++++++-----
> > 1 file changed, 34 insertions(+), 5 deletions(-)
> >
> > diff --git a/drivers/scsi/ufs/ufshcd.c b/drivers/scsi/ufs/ufshcd.c
> > index 307622284239..fc01171d13b1 100644
> > --- a/drivers/scsi/ufs/ufshcd.c
> > +++ b/drivers/scsi/ufs/ufshcd.c
> > @@ -159,6 +159,12 @@ struct ufs_pm_lvl_states ufs_pm_lvl_states[] = {
> > {UFS_POWERDOWN_PWR_MODE, UIC_LINK_OFF_STATE},
> > };
> >
> > +#define ufshcd_scsi_for_each_sdev(fn) \
> > + list_for_each_entry(starget, &hba->host->__targets, siblings) { \
> > + __starget_for_each_device(starget, NULL, \
> > + fn); \
> > + }
> > +
> > static inline enum ufs_dev_pwr_mode
> > ufs_get_pm_lvl_to_dev_pwr_mode(enum ufs_pm_level lvl)
> > {
> > @@ -8629,6 +8635,13 @@ int ufshcd_runtime_idle(struct ufs_hba *hba)
> > }
> > EXPORT_SYMBOL(ufshcd_runtime_idle);
> >
> > +static void ufshcd_quiesce_sdev(struct scsi_device *sdev, void *data)
> > +{
> > + /* Suspended devices are already quiesced so can be skipped */
>
> Why can runtime suspended sdevs be skipped? Block layer can still resume
> them at any time, no?
Thanks for reminding.
Yes, this check is wrong. All SCSI devices shall be applied
scsi_device_quiesce() here so I will fix it in next version.
>
> > + if (!pm_runtime_suspended(&sdev->sdev_gendev))
> > + scsi_device_quiesce(sdev);
> > +}
> > +
> > /**
> > * ufshcd_shutdown - shutdown routine
> > * @hba: per adapter instance
> > @@ -8640,6 +8653,7 @@ EXPORT_SYMBOL(ufshcd_runtime_idle);
> > int ufshcd_shutdown(struct ufs_hba *hba)
> > {
> > int ret = 0;
> > + struct scsi_target *starget;
> >
> > if (!hba->is_powered)
> > goto out;
> > @@ -8647,11 +8661,26 @@ int ufshcd_shutdown(struct ufs_hba *hba)
> > if (ufshcd_is_ufs_dev_poweroff(hba) && ufshcd_is_link_off(hba))
> > goto out;
> >
> > - if (pm_runtime_suspended(hba->dev)) {
> > - ret = ufshcd_runtime_resume(hba);
> > - if (ret)
> > - goto out;
> > - }
> > + /*
> > + * Let runtime PM framework manage and prevent concurrent runtime
> > + * operations with shutdown flow.
> > + */
> > + pm_runtime_get_sync(hba->dev);
> > +
> > + /*
> > + * Quiesce all SCSI devices to prevent any non-PM requests sending
> > + * from block layer during and after shutdown.
> > + *
> > + * Here we can not use blk_cleanup_queue() since PM requests
> > + * (with BLK_MQ_REQ_PREEMPT flag) are still required to be sent
> > + * through block layer. Therefore SCSI command queued after the
> > + * scsi_target_quiesce() call returned will block until
> > + * blk_cleanup_queue() is called.
> > + *
> > + * Besides, scsi_target_"un"quiesce (e.g., scsi_target_resume) can
> > + * be ignored since shutdown is one-way flow.
> > + */
> > + ufshcd_scsi_for_each_sdev(ufshcd_quiesce_sdev);
>
> Any reasons why don't use scsi_target_quiesce() here?
As above, now all SCSI devices shall be quiesced here, so I could use
the way in v2: using scsi_target_quiesce() directly here.
Thanks,
Stanley Chu
>
> Thanks,
>
> Can Guo.
>
> >
> > ret = ufshcd_suspend(hba, UFS_SHUTDOWN_PM);
> > out:
_______________________________________________
Linux-mediatek mailing list
Linux-mediatek@lists.infradead.org
http://lists.infradead.org/mailman/listinfo/linux-mediatek
^ permalink raw reply [flat|nested] 9+ messages in thread* Re: [PATCH v6] scsi: ufs: Quiesce all scsi devices before shutdown
@ 2020-08-03 9:58 ` Stanley Chu
0 siblings, 0 replies; 9+ messages in thread
From: Stanley Chu @ 2020-08-03 9:58 UTC (permalink / raw)
To: Can Guo
Cc: jiajie.hao, linux-scsi, martin.petersen, andy.teng, jejb,
chun-hung.wu, kuohong.wang, linux-kernel, asutoshd, avri.altman,
linux-mediatek, peter.wang, alim.akhtar, matthias.bgg, beanhuo,
chaotian.jing, cc.chou, linux-arm-kernel, bvanassche
Hi Can,
On Mon, 2020-08-03 at 13:03 +0800, Can Guo wrote:
> Hi Stanley,
>
> On 2020-08-03 12:25, Stanley Chu wrote:
> > Currently I/O request could be still submitted to UFS device while
> > UFS is working on shutdown flow. This may lead to racing as below
> > scenarios and finally system may crash due to unclocked register
> > accesses.
> >
> > To fix this kind of issues, in ufshcd_shutdown(),
> >
> > 1. Use pm_runtime_get_sync() instead of resuming UFS device by
> > ufshcd_runtime_resume() "internally" to let runtime PM framework
> > manage and prevent concurrent runtime operations by incoming I/O
> > requests.
> >
> > 2. Specifically quiesce all SCSI devices to block all I/O requests
> > after device is resumed.
> >
> > Example of racing scenario: While UFS device is runtime-suspended
> >
> > Thread #1: Executing UFS shutdown flow, e.g.,
> > ufshcd_suspend(UFS_SHUTDOWN_PM)
> >
> > Thread #2: Executing runtime resume flow triggered by I/O request,
> > e.g., ufshcd_resume(UFS_RUNTIME_PM)
> >
> > This breaks the assumption that UFS PM flows can not be running
> > concurrently and some unexpected racing behavior may happen.
> >
> > Signed-off-by: Stanley Chu <stanley.chu@mediatek.com>
> > ---
> > Changes:
> > - Since v4: Use pm_runtime_get_sync() instead of resuming UFS device
> > by ufshcd_runtime_resume() "internally".
> > ---
> > drivers/scsi/ufs/ufshcd.c | 39 ++++++++++++++++++++++++++++++++++-----
> > 1 file changed, 34 insertions(+), 5 deletions(-)
> >
> > diff --git a/drivers/scsi/ufs/ufshcd.c b/drivers/scsi/ufs/ufshcd.c
> > index 307622284239..fc01171d13b1 100644
> > --- a/drivers/scsi/ufs/ufshcd.c
> > +++ b/drivers/scsi/ufs/ufshcd.c
> > @@ -159,6 +159,12 @@ struct ufs_pm_lvl_states ufs_pm_lvl_states[] = {
> > {UFS_POWERDOWN_PWR_MODE, UIC_LINK_OFF_STATE},
> > };
> >
> > +#define ufshcd_scsi_for_each_sdev(fn) \
> > + list_for_each_entry(starget, &hba->host->__targets, siblings) { \
> > + __starget_for_each_device(starget, NULL, \
> > + fn); \
> > + }
> > +
> > static inline enum ufs_dev_pwr_mode
> > ufs_get_pm_lvl_to_dev_pwr_mode(enum ufs_pm_level lvl)
> > {
> > @@ -8629,6 +8635,13 @@ int ufshcd_runtime_idle(struct ufs_hba *hba)
> > }
> > EXPORT_SYMBOL(ufshcd_runtime_idle);
> >
> > +static void ufshcd_quiesce_sdev(struct scsi_device *sdev, void *data)
> > +{
> > + /* Suspended devices are already quiesced so can be skipped */
>
> Why can runtime suspended sdevs be skipped? Block layer can still resume
> them at any time, no?
Thanks for reminding.
Yes, this check is wrong. All SCSI devices shall be applied
scsi_device_quiesce() here so I will fix it in next version.
>
> > + if (!pm_runtime_suspended(&sdev->sdev_gendev))
> > + scsi_device_quiesce(sdev);
> > +}
> > +
> > /**
> > * ufshcd_shutdown - shutdown routine
> > * @hba: per adapter instance
> > @@ -8640,6 +8653,7 @@ EXPORT_SYMBOL(ufshcd_runtime_idle);
> > int ufshcd_shutdown(struct ufs_hba *hba)
> > {
> > int ret = 0;
> > + struct scsi_target *starget;
> >
> > if (!hba->is_powered)
> > goto out;
> > @@ -8647,11 +8661,26 @@ int ufshcd_shutdown(struct ufs_hba *hba)
> > if (ufshcd_is_ufs_dev_poweroff(hba) && ufshcd_is_link_off(hba))
> > goto out;
> >
> > - if (pm_runtime_suspended(hba->dev)) {
> > - ret = ufshcd_runtime_resume(hba);
> > - if (ret)
> > - goto out;
> > - }
> > + /*
> > + * Let runtime PM framework manage and prevent concurrent runtime
> > + * operations with shutdown flow.
> > + */
> > + pm_runtime_get_sync(hba->dev);
> > +
> > + /*
> > + * Quiesce all SCSI devices to prevent any non-PM requests sending
> > + * from block layer during and after shutdown.
> > + *
> > + * Here we can not use blk_cleanup_queue() since PM requests
> > + * (with BLK_MQ_REQ_PREEMPT flag) are still required to be sent
> > + * through block layer. Therefore SCSI command queued after the
> > + * scsi_target_quiesce() call returned will block until
> > + * blk_cleanup_queue() is called.
> > + *
> > + * Besides, scsi_target_"un"quiesce (e.g., scsi_target_resume) can
> > + * be ignored since shutdown is one-way flow.
> > + */
> > + ufshcd_scsi_for_each_sdev(ufshcd_quiesce_sdev);
>
> Any reasons why don't use scsi_target_quiesce() here?
As above, now all SCSI devices shall be quiesced here, so I could use
the way in v2: using scsi_target_quiesce() directly here.
Thanks,
Stanley Chu
>
> Thanks,
>
> Can Guo.
>
> >
> > ret = ufshcd_suspend(hba, UFS_SHUTDOWN_PM);
> > out:
_______________________________________________
linux-arm-kernel mailing list
linux-arm-kernel@lists.infradead.org
http://lists.infradead.org/mailman/listinfo/linux-arm-kernel
^ permalink raw reply [flat|nested] 9+ messages in thread* Re: [PATCH v6] scsi: ufs: Quiesce all scsi devices before shutdown
@ 2020-08-03 9:58 ` Stanley Chu
0 siblings, 0 replies; 9+ messages in thread
From: Stanley Chu @ 2020-08-03 9:58 UTC (permalink / raw)
To: Can Guo
Cc: linux-scsi, martin.petersen, avri.altman, alim.akhtar, jejb,
bvanassche, beanhuo, asutoshd, matthias.bgg, linux-mediatek,
linux-arm-kernel, linux-kernel, kuohong.wang, peter.wang,
chun-hung.wu, andy.teng, chaotian.jing, cc.chou, jiajie.hao
Hi Can,
On Mon, 2020-08-03 at 13:03 +0800, Can Guo wrote:
> Hi Stanley,
>
> On 2020-08-03 12:25, Stanley Chu wrote:
> > Currently I/O request could be still submitted to UFS device while
> > UFS is working on shutdown flow. This may lead to racing as below
> > scenarios and finally system may crash due to unclocked register
> > accesses.
> >
> > To fix this kind of issues, in ufshcd_shutdown(),
> >
> > 1. Use pm_runtime_get_sync() instead of resuming UFS device by
> > ufshcd_runtime_resume() "internally" to let runtime PM framework
> > manage and prevent concurrent runtime operations by incoming I/O
> > requests.
> >
> > 2. Specifically quiesce all SCSI devices to block all I/O requests
> > after device is resumed.
> >
> > Example of racing scenario: While UFS device is runtime-suspended
> >
> > Thread #1: Executing UFS shutdown flow, e.g.,
> > ufshcd_suspend(UFS_SHUTDOWN_PM)
> >
> > Thread #2: Executing runtime resume flow triggered by I/O request,
> > e.g., ufshcd_resume(UFS_RUNTIME_PM)
> >
> > This breaks the assumption that UFS PM flows can not be running
> > concurrently and some unexpected racing behavior may happen.
> >
> > Signed-off-by: Stanley Chu <stanley.chu@mediatek.com>
> > ---
> > Changes:
> > - Since v4: Use pm_runtime_get_sync() instead of resuming UFS device
> > by ufshcd_runtime_resume() "internally".
> > ---
> > drivers/scsi/ufs/ufshcd.c | 39 ++++++++++++++++++++++++++++++++++-----
> > 1 file changed, 34 insertions(+), 5 deletions(-)
> >
> > diff --git a/drivers/scsi/ufs/ufshcd.c b/drivers/scsi/ufs/ufshcd.c
> > index 307622284239..fc01171d13b1 100644
> > --- a/drivers/scsi/ufs/ufshcd.c
> > +++ b/drivers/scsi/ufs/ufshcd.c
> > @@ -159,6 +159,12 @@ struct ufs_pm_lvl_states ufs_pm_lvl_states[] = {
> > {UFS_POWERDOWN_PWR_MODE, UIC_LINK_OFF_STATE},
> > };
> >
> > +#define ufshcd_scsi_for_each_sdev(fn) \
> > + list_for_each_entry(starget, &hba->host->__targets, siblings) { \
> > + __starget_for_each_device(starget, NULL, \
> > + fn); \
> > + }
> > +
> > static inline enum ufs_dev_pwr_mode
> > ufs_get_pm_lvl_to_dev_pwr_mode(enum ufs_pm_level lvl)
> > {
> > @@ -8629,6 +8635,13 @@ int ufshcd_runtime_idle(struct ufs_hba *hba)
> > }
> > EXPORT_SYMBOL(ufshcd_runtime_idle);
> >
> > +static void ufshcd_quiesce_sdev(struct scsi_device *sdev, void *data)
> > +{
> > + /* Suspended devices are already quiesced so can be skipped */
>
> Why can runtime suspended sdevs be skipped? Block layer can still resume
> them at any time, no?
Thanks for reminding.
Yes, this check is wrong. All SCSI devices shall be applied
scsi_device_quiesce() here so I will fix it in next version.
>
> > + if (!pm_runtime_suspended(&sdev->sdev_gendev))
> > + scsi_device_quiesce(sdev);
> > +}
> > +
> > /**
> > * ufshcd_shutdown - shutdown routine
> > * @hba: per adapter instance
> > @@ -8640,6 +8653,7 @@ EXPORT_SYMBOL(ufshcd_runtime_idle);
> > int ufshcd_shutdown(struct ufs_hba *hba)
> > {
> > int ret = 0;
> > + struct scsi_target *starget;
> >
> > if (!hba->is_powered)
> > goto out;
> > @@ -8647,11 +8661,26 @@ int ufshcd_shutdown(struct ufs_hba *hba)
> > if (ufshcd_is_ufs_dev_poweroff(hba) && ufshcd_is_link_off(hba))
> > goto out;
> >
> > - if (pm_runtime_suspended(hba->dev)) {
> > - ret = ufshcd_runtime_resume(hba);
> > - if (ret)
> > - goto out;
> > - }
> > + /*
> > + * Let runtime PM framework manage and prevent concurrent runtime
> > + * operations with shutdown flow.
> > + */
> > + pm_runtime_get_sync(hba->dev);
> > +
> > + /*
> > + * Quiesce all SCSI devices to prevent any non-PM requests sending
> > + * from block layer during and after shutdown.
> > + *
> > + * Here we can not use blk_cleanup_queue() since PM requests
> > + * (with BLK_MQ_REQ_PREEMPT flag) are still required to be sent
> > + * through block layer. Therefore SCSI command queued after the
> > + * scsi_target_quiesce() call returned will block until
> > + * blk_cleanup_queue() is called.
> > + *
> > + * Besides, scsi_target_"un"quiesce (e.g., scsi_target_resume) can
> > + * be ignored since shutdown is one-way flow.
> > + */
> > + ufshcd_scsi_for_each_sdev(ufshcd_quiesce_sdev);
>
> Any reasons why don't use scsi_target_quiesce() here?
As above, now all SCSI devices shall be quiesced here, so I could use
the way in v2: using scsi_target_quiesce() directly here.
Thanks,
Stanley Chu
>
> Thanks,
>
> Can Guo.
>
> >
> > ret = ufshcd_suspend(hba, UFS_SHUTDOWN_PM);
> > out:
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