On 6/15/23 17:41, Hannes Reinecke wrote: > On 6/15/23 10:33, Damien Le Moal wrote: >> When an ATA port is resumed from sleep, the port is reset and a power >> management request issued to libata EH to reset the port and rescanning >> the device(s) attached to the port. Device rescanning is done by >> scheduling an ata_scsi_dev_rescan() work, which will execute >> scsi_rescan_device(). >> >> However, scsi_rescan_device() takes the generic device lock, which is >> also taken by dpm_resume() when the SCSI device is resumed as well. If >> a device rescan execution starts before the completion of the SCSI >> device resume, the rcu locking used to refresh the cached VPD pages of >> the device, combined with the generic device locking from >> scsi_rescan_device() and from dpm_resume() can cause a deadlock. >> >> Avoid this situation by changing struct ata_port scsi_rescan_task to be >> a delayed work instead of a simple work_struct. ata_scsi_dev_rescan() is >> modified to check if the SCSI device associated with the ATA device that >> must be rescanned is not suspended. If the SCSI device is still >> suspended, ata_scsi_dev_rescan() returns early and reschedule itself for >> execution after an arbitrary delay of 5ms. >> >> Reported-by: Kai-Heng Feng <kai.heng.feng@xxxxxxxxxxxxx> >> Reported-by: Joe Breuer <linux-kernel@xxxxxxxxxxxx> >> Closes: https://bugzilla.kernel.org/show_bug.cgi?id=217530 >> Fixes: a19a93e4c6a9 ("scsi: core: pm: Rely on the device driver core for async power management") >> Signed-off-by: Damien Le Moal <dlemoal@xxxxxxxxxx> >> --- >> drivers/ata/libata-core.c | 3 ++- >> drivers/ata/libata-eh.c | 2 +- >> drivers/ata/libata-scsi.c | 22 +++++++++++++++++++++- >> include/linux/libata.h | 2 +- >> 4 files changed, 25 insertions(+), 4 deletions(-) >> >> diff --git a/drivers/ata/libata-core.c b/drivers/ata/libata-core.c >> index 8bf612bdd61a..b4f246f0cac7 100644 >> --- a/drivers/ata/libata-core.c >> +++ b/drivers/ata/libata-core.c >> @@ -5348,7 +5348,7 @@ struct ata_port *ata_port_alloc(struct ata_host *host) >> >> mutex_init(&ap->scsi_scan_mutex); >> INIT_DELAYED_WORK(&ap->hotplug_task, ata_scsi_hotplug); >> - INIT_WORK(&ap->scsi_rescan_task, ata_scsi_dev_rescan); >> + INIT_DELAYED_WORK(&ap->scsi_rescan_task, ata_scsi_dev_rescan); >> INIT_LIST_HEAD(&ap->eh_done_q); >> init_waitqueue_head(&ap->eh_wait_q); >> init_completion(&ap->park_req_pending); >> @@ -5954,6 +5954,7 @@ static void ata_port_detach(struct ata_port *ap) >> WARN_ON(!(ap->pflags & ATA_PFLAG_UNLOADED)); >> >> cancel_delayed_work_sync(&ap->hotplug_task); >> + cancel_delayed_work_sync(&ap->scsi_rescan_task); >> >> skip_eh: >> /* clean up zpodd on port removal */ >> diff --git a/drivers/ata/libata-eh.c b/drivers/ata/libata-eh.c >> index a6c901811802..6f8d14191593 100644 >> --- a/drivers/ata/libata-eh.c >> +++ b/drivers/ata/libata-eh.c >> @@ -2984,7 +2984,7 @@ static int ata_eh_revalidate_and_attach(struct ata_link *link, >> ehc->i.flags |= ATA_EHI_SETMODE; >> >> /* schedule the scsi_rescan_device() here */ >> - schedule_work(&(ap->scsi_rescan_task)); >> + schedule_delayed_work(&ap->scsi_rescan_task, 0); >> } else if (dev->class == ATA_DEV_UNKNOWN && >> ehc->tries[dev->devno] && >> ata_class_enabled(ehc->classes[dev->devno])) { >> diff --git a/drivers/ata/libata-scsi.c b/drivers/ata/libata-scsi.c >> index 8ce90284eb34..551077cea4e4 100644 >> --- a/drivers/ata/libata-scsi.c >> +++ b/drivers/ata/libata-scsi.c >> @@ -4597,10 +4597,11 @@ int ata_scsi_user_scan(struct Scsi_Host *shost, unsigned int channel, >> void ata_scsi_dev_rescan(struct work_struct *work) >> { >> struct ata_port *ap = >> - container_of(work, struct ata_port, scsi_rescan_task); >> + container_of(work, struct ata_port, scsi_rescan_task.work); >> struct ata_link *link; >> struct ata_device *dev; >> unsigned long flags; >> + bool delay_rescan = false; >> >> mutex_lock(&ap->scsi_scan_mutex); >> spin_lock_irqsave(ap->lock, flags); >> @@ -4614,6 +4615,21 @@ void ata_scsi_dev_rescan(struct work_struct *work) >> if (scsi_device_get(sdev)) >> continue; >> >> + /* >> + * If the rescan work was scheduled because of a resume >> + * event, the port is already fully resumed, but the >> + * SCSI device may not yet be fully resumed. In such >> + * case, executing scsi_rescan_device() may cause a >> + * deadlock with the PM code on device_lock(). Prevent >> + * this by giving up and retrying rescan after a short >> + * delay. >> + */ >> + delay_rescan = sdev->sdev_gendev.power.is_suspended; >> + if (delay_rescan) { >> + scsi_device_put(sdev); >> + break; >> + } >> + >> spin_unlock_irqrestore(ap->lock, flags); >> scsi_rescan_device(&(sdev->sdev_gendev)); >> scsi_device_put(sdev); >> @@ -4623,4 +4639,8 @@ void ata_scsi_dev_rescan(struct work_struct *work) >> >> spin_unlock_irqrestore(ap->lock, flags); >> mutex_unlock(&ap->scsi_scan_mutex); >> + >> + if (delay_rescan) >> + schedule_delayed_work(&ap->scsi_rescan_task, >> + msecs_to_jiffies(5)); >> } >> diff --git a/include/linux/libata.h b/include/linux/libata.h >> index 311cd93377c7..dd5797fb6305 100644 >> --- a/include/linux/libata.h >> +++ b/include/linux/libata.h >> @@ -836,7 +836,7 @@ struct ata_port { >> >> struct mutex scsi_scan_mutex; >> struct delayed_work hotplug_task; >> - struct work_struct scsi_rescan_task; >> + struct delayed_work scsi_rescan_task; >> >> unsigned int hsm_task_state; >> > > Hehe. That is exactly what I had in mind. The direct test of "is_suspended" is not exactly pretty. But there are a few drivers doing it... So, it will have to do for now. > > Reviewed-by: Hannes Reinecke <hare@xxxxxxx> > > Cheers, > > Hannes > -- Damien Le Moal Western Digital Research
