Messages in this thread | | | Date | Mon, 03 Aug 2020 13:03:16 +0800 | From | Can Guo <> | Subject | Re: [PATCH v6] scsi: ufs: Quiesce all scsi devices before shutdown |
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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:
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