Re: [PATCH v3] scsi: libsas: fix HA resume deadlock and hisi_sas disk-wake race

[John Garry <john.g.garry@oracle.com>]

On 16/07/2026 09:11, Xingui Yang wrote:
> Commit fbefe22811c3140 ("scsi: libsas: Don't always drain event workqueue
> for HA resume") introduced sas_resume_ha_no_sync() to avoid a deadlock:
> the PHYE_RESUME_TIMEOUT handler, running on the HA event workqueue, calls
> sas_deform_port() -> sas_destruct_devices(), which removes SCSI devices and
> waits for the host to become runtime-active. But the host cannot resume
> until sas_resume_ha() -> sas_drain_work() returns, and the drain is blocked
> on that very handler.
> 
> However skipping the drain reintroduces a race: hisi_sas returns from
> resume before all PHY UP work and libsas discovery work finish. The
> controller may then autosuspend while disks are still waking up. The disks
> issue IO to a suspended controller, the IO fails, and the disks get
> disabled.
> 
> Fix the deadlock at its source by moving the PHYE_RESUME_TIMEOUT
> notification to after sas_drain_work(). By then the host resume is about to
> complete, so device removal through device_link no longer blocks on the
> resume and the cycle is broken.
> 
> With the deadlock gone, restore sas_resume_ha() (the draining variant) in
> hisi_sas and remove sas_resume_ha_no_sync().
> 
> The reorder is safe for the other libsas consumers (isci, pm8001, aic94xx,
> mvsas). During suspend, sas_suspend_devices() calls
> sas_notify_lldd_dev_gone() for each device, which sets dev->lldd_dev to
> NULL. When scsi_unblock_requests re-enables I/O in resume, any I/O to a
> timed-out phy's disk is immediately rejected by the LLDD before reaching
> hardware: isci returns SAS_DEVICE_UNKNOWN (mapped to DID_BAD_TARGET), and
> pm8001 returns SAS_PHY_DOWN (mapped to DID_NO_CONNECT). Both complete
> directly via scsi_done() without entering SCSI EH. This is identical in
> both the old and new ordering since lldd_dev_gone runs during suspend,
> before resume. The reorder only affects when the PHYE_RESUME_TIMEOUT
> handler runs (synchronized by sas_drain_work() vs. asynchronous after
> resume returns), not whether I/O can reach the device. aic94xx and mvsas
> do not register any PM ops and never reach this code path.
> 
> Fixes: fbefe22811c3140 ("scsi: libsas: Don't always drain event workqueue for HA resume")
> Signed-off-by: Xingui Yang<yangxingui@huawei.com>

Can this possibly be tested on another SCSI HBA which uses libsas? And 
using SATA disks.