On 6/15/23 17:33, 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. Joe, Kai-Heng, I cannot recreate the issue on my test machines. So it would be great if you could test this new candidate fix. It is not exactly pretty, but a real fix needs a lot more work and more testing. So that will be for later. > > 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; > -- Damien Le Moal Western Digital Research
