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

[sashiko-bot@kernel.org]

Thank you for your contribution! Sashiko AI review found 2 potential issue(s) to consider:

New issues:
- [High] The `flush_workqueue(hisi_hba->wq)` placement is ineffective, failing to prevent the autosuspend race for newly discovered PHYs.

Pre-existing issues:
- [High] PHY down events are silently dropped during resume because `HISI_SAS_RESETTING_BIT` remains set, permanently leaving libsas state out of sync.
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commit ce8bc2a47295d4675bf4efa43c713662a8cd5696
Author: Xingui Yang <yangxingui@huawei.com>

scsi: libsas: fix HA resume deadlock and hisi_sas disk-wake race

This patch resolves a deadlock during HA resume by moving the
PHYE_RESUME_TIMEOUT notification to after sas_drain_work(). It restores
the draining sas_resume_ha() behavior in hisi_sas and introduces a
flush_workqueue() to prevent an autosuspend race.

> diff --git a/drivers/scsi/hisi_sas/hisi_sas_v3_hw.c b/drivers/scsi/hisi_sas/hisi_sas_v3_hw.c
> index 213d5b5dea94f..901f508e8be77 100644
> --- a/drivers/scsi/hisi_sas/hisi_sas_v3_hw.c
> +++ b/drivers/scsi/hisi_sas/hisi_sas_v3_hw.c
> @@ -5262,14 +5262,8 @@ static int _resume_v3_hw(struct device *device)
>  	}
>  	phys_init_v3_hw(hisi_hba);
>  
> -	/*
> -	 * If a directly-attached disk is removed during suspend, a deadlock
> -	 * may occur, as the PHYE_RESUME_TIMEOUT processing will require the
> -	 * hisi_hba->device to be active, which can only happen when resume
> -	 * completes. So don't wait for the HA event workqueue to drain upon
> -	 * resume.
> -	 */
> -	sas_resume_ha_no_sync(sha);
> +	sas_resume_ha(sha);
> +	flush_workqueue(hisi_hba->wq);

[Severity: High]
Does this flush_workqueue() placement miss newly queued discovery events?

sas_resume_ha() drains the libsas event_q and disco_q. By flushing hisi_hba->wq
after this drain, any hisi_sas_phyup_pm_work items on hisi_hba->wq will queue
PORTE_BYTES_DMAED events to event_q that bypass the drain.

Since hisi_sas_phyup_pm_work then calls pm_runtime_put_sync(), its PM reference
is dropped. When _resume_v3_hw() returns, the system PM reference is also
dropped, allowing the controller to autosuspend while the missed discovery
works execute asynchronously and attempt to send IO to a suspended controller.

Should the flush be placed before sas_resume_ha() so the generated events are
caught and synchronously processed by sas_drain_work()?

>  	clear_bit(HISI_SAS_RESETTING_BIT, &hisi_hba->flags);

[Severity: High]
This is a pre-existing issue, but are PHY down events silently dropped during
resume because HISI_SAS_RESETTING_BIT remains set?

In _resume_v3_hw(), HISI_SAS_RESETTING_BIT is kept active across the
sas_resume_ha() call. If a PHY loses its link during this time, the hardware
interrupt handler drops the event:

drivers/scsi/hisi_sas/hisi_sas_main.c:hisi_sas_phy_down() {
		if (test_bit(HISI_SAS_RESETTING_BIT, &hisi_hba->flags) ||
		    phy->in_reset) {
			dev_info(dev, "ignore flutter phy%d down\n", phy_no);
			return;
		}
}

When HISI_SAS_RESETTING_BIT is finally cleared here, it does not call
hisi_sas_rescan_topology() to recover dropped events. Could this permanently
leave libsas state out of sync if a PHY disconnects during the resume wait?

>  
>  	dev_warn(dev, "end of resuming controller\n");

-- 
Sashiko AI review · https://sashiko.dev/#/patchset/20260630065157.421203-1-yangxingui@huawei.com?part=1