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Petersen (Oracle)" , Sasha Levin Subject: [PATCH 6.6 031/168] scsi: libsas: Fix SMP IO deadlock during HA resume Date: Wed, 28 Oct 2026 17:59:27 +0100 Message-ID: <20261028165943.833514220@linuxfoundation.org> X-Mailer: git-send-email 2.56.0 In-Reply-To: <20261028165943.089486480@linuxfoundation.org> References: <20261028165943.089486480@linuxfoundation.org> User-Agent: quilt/0.69 X-stable: review X-Patchwork-Hint: ignore X-Mailing-List: patches@lists.linux.dev List-Id: List-Post: List-Help: List-Subscribe: List-Unsubscribe: List-Owner: Precedence: list MIME-Version: 1.0 Content-Transfer-Encoding: 8bit 6.6-stable review patch. If anyone has any objections, please let me know. ------------------ From: Xingui Yang [ Upstream commit 81e097a064b28b4a1f6ca1a8b433e659c1bd64c0 ] smp_execute_task_sg() calls pm_runtime_get_sync() on the host before issuing an SMP command. When that command is itself issued from the HA resume path, the get_sync() deadlocks: it waits for the ongoing resume (the device is RPM_RESUMING), while the resume is blocked in sas_drain_work() waiting for that same SMP IO to complete. The deadlock needs an expander-attached SATA disk. During sas_resume_ha() -> sas_drain_work(), DISCE_RESUME -> sas_resume_sata() -> ata_sas_port_resume() requests ATA_EH_RESET, and the hard reset for such a disk is done via SMP PHY CONTROL (sas_ata_hard_reset() -> sas_phy_reset() -> sas_smp_phy_control() -> smp_execute_task_sg()). Direct-attached SATA resets through lldd_control_phy() and SSP devices use TMFs, so neither hits this. Replace the get_sync()/put_sync() pair with pm_runtime_get_noresume()/pm_runtime_put(). smp_execute_task_sg() only needs to hold off autosuspend while the SMP is in flight, and it must not try to resume the host: a sync resume issued from the HA resume path itself is what deadlocks, and by the time sas_resume_ha() runs, hw_init has already reinitialized the hardware, so the device is accessible without one. The usage reference is still required. Discovery work normally runs inside an event worker's PM reference, taken at sas_notify_port_event() notify time and held until the handler has flushed the disco queue. sas_rediscover_ex_phy() however requeues DISCE_REVALIDATE_DOMAIN from within the revalidation worker itself, and flush_workqueue() does not wait for work items queued during execution, so that chained revalidation runs with no outer PM reference - without the get_noresume(), its SMP could race autosuspend. For the BSG path, sas_smp_handler() is the only caller which may find the host autosuspended: expander SMP requests do not go through any SCSI device request queue, so nothing else in that path holds the host awake. Resume it there with pm_runtime_resume_and_get() and check the result. Fixes: 3dbbbf656b850 ("scsi: libsas: Fix HA resume deadlock and hisi_sas disk-wake race") Signed-off-by: Xingui Yang Reviewed-by: John Garry Link: https://patch.msgid.link/20260928040234.992912-1-yangxingui@huawei.com Signed-off-by: Martin K. Petersen (Oracle) Signed-off-by: Sasha Levin --- drivers/scsi/libsas/sas_expander.c | 14 ++++++++++++-- 1 file changed, 12 insertions(+), 2 deletions(-) diff --git a/drivers/scsi/libsas/sas_expander.c b/drivers/scsi/libsas/sas_expander.c index e97f4e01a865a..16cc1c14b9f45 100644 --- a/drivers/scsi/libsas/sas_expander.c +++ b/drivers/scsi/libsas/sas_expander.c @@ -40,7 +40,11 @@ static int smp_execute_task_sg(struct domain_device *dev, to_sas_internal(dev->port->ha->shost->transportt); struct sas_ha_struct *ha = dev->port->ha; - pm_runtime_get_sync(ha->dev); + /* + * Non-blocking: a sync resume here would deadlock against + * sas_drain_work() during HA resume. + */ + pm_runtime_get_noresume(ha->dev); mutex_lock(&dev->ex_dev.cmd_mutex); for (retry = 0; retry < 3; retry++) { if (test_bit(SAS_DEV_GONE, &dev->state)) { @@ -113,7 +117,7 @@ static int smp_execute_task_sg(struct domain_device *dev, } } mutex_unlock(&dev->ex_dev.cmd_mutex); - pm_runtime_put_sync(ha->dev); + pm_runtime_put(ha->dev); BUG_ON(retry == 3 && task != NULL); sas_free_task(task); @@ -2142,6 +2146,11 @@ void sas_smp_handler(struct bsg_job *job, struct Scsi_Host *shost, goto out; } + /* The host may have autosuspended, resume it here. */ + ret = pm_runtime_resume_and_get(dev->port->ha->dev); + if (ret) + goto out; + ret = smp_execute_task_sg(dev, job->request_payload.sg_list, job->reply_payload.sg_list); if (ret >= 0) { @@ -2149,6 +2158,7 @@ void sas_smp_handler(struct bsg_job *job, struct Scsi_Host *shost, rcvlen = job->reply_payload.payload_len - ret; ret = 0; } + pm_runtime_put(dev->port->ha->dev); out: bsg_job_done(job, ret, rcvlen); -- 2.53.0