ahci: prevent freezing port when EH is running

euler inclusion
category: bugfix
bugzilla: NA
CVE: NA

---------------------------

Trinity report a warning for this patch:
WARNING: CPU: 1 PID: 118 at ../drivers/ata/libata-eh.c:4016
ata_eh_finish+0x15a/0x170

Fixing the race condition between EH and interrupt by making the EH
thread re-enter again is a little overkill and IO will get through
after the scsi_run_host_queues() and before SHOST_RECOVERY is set agian
in scsi_restart_operations().

If EH thread is already running, no need to freeze port and schedule
EH again.

Fixes: a7d2fef75b83 ("scsi: ata: Fix a race condition between scsi error handler and ahci interrupt")
Signed-off-by: NJason Yan <yanaijie@huawei.com>
Reviewed-by: Nzhengbin <zhengbin13@huawei.com>
Signed-off-by: NYang Yingliang <yangyingliang@huawei.com>

drivers/ata/libahci.c

@@ -1805,9 +1805,17 @@ static void ahci_error_intr(struct ata_port *ap, u32 irq_stat)
 
 	/* okay, let's hand over to EH */
 
-	if (irq_stat & PORT_IRQ_FREEZE)
+	if (irq_stat & PORT_IRQ_FREEZE) {
+		/*
+		 * EH already running, this may happen if the port is
+		 * thawed in the EH. But we cannot freeze it again
+		 * otherwise the port will never be thawed.
+		 */
+		if (ap->pflags & (ATA_PFLAG_EH_PENDING |
+			ATA_PFLAG_EH_IN_PROGRESS))
+			return;
 		ata_port_freeze(ap);
-	else if (fbs_need_dec) {
+	} else if (fbs_need_dec) {
 		ata_link_abort(link);
 		ahci_fbs_dec_intr(ap);
 	} else

drivers/ata/libata-eh.c

@@ -974,7 +974,7 @@ void ata_std_end_eh(struct ata_port *ap)
 {
 	struct Scsi_Host *host = ap->scsi_host;
 
-	atomic_dec(&host->host_eh_scheduled);
+	host->host_eh_scheduled = 0;
 }
 EXPORT_SYMBOL(ata_std_end_eh);
 

drivers/scsi/libsas/sas_scsi_host.c

@@ -492,7 +492,7 @@ int sas_eh_abort_handler(struct scsi_cmnd *cmd)
 
 	spin_lock_irqsave(host->host_lock, flags);
 	/* We cannot do async aborts for SATA devices */
-	if (dev_is_sata(dev) && !atomic_read(&host->host_eh_scheduled)) {
+	if (dev_is_sata(dev) && !host->host_eh_scheduled) {
 		spin_unlock_irqrestore(host->host_lock, flags);
 		return FAILED;
 	}
@@ -792,7 +792,7 @@ void sas_scsi_recover_host(struct Scsi_Host *shost)
 	/* check if any new eh work was scheduled during the last run */
 	spin_lock_irq(&ha->lock);
 	if (ha->eh_active == 0) {
-		atomic_set(&shost->host_eh_scheduled, 0);
+		shost->host_eh_scheduled = 0;
 		retry = false;
 	}
 	spin_unlock_irq(&ha->lock);

drivers/scsi/scsi_error.c

@@ -88,7 +88,7 @@ void scsi_schedule_eh(struct Scsi_Host *shost)
 
 	if (scsi_host_set_state(shost, SHOST_RECOVERY) == 0 ||
 	    scsi_host_set_state(shost, SHOST_CANCEL_RECOVERY) == 0) {
-		atomic_inc(&shost->host_eh_scheduled);
+		shost->host_eh_scheduled++;
 		scsi_eh_wakeup(shost);
 	}
 
@@ -2029,7 +2029,7 @@ static void scsi_restart_operations(struct Scsi_Host *shost)
 	 * pending commands complete.
 	 */
 	spin_lock_irqsave(shost->host_lock, flags);
-	if (atomic_read(&shost->host_eh_scheduled))
+	if (shost->host_eh_scheduled)
 		if (scsi_host_set_state(shost, SHOST_RECOVERY))
 			WARN_ON(scsi_host_set_state(shost, SHOST_CANCEL_RECOVERY));
 	spin_unlock_irqrestore(shost->host_lock, flags);
@@ -2165,8 +2165,7 @@ int scsi_error_handler(void *data)
 		if (kthread_should_stop())
 			break;
 
-		if ((shost->host_failed == 0 &&
-		     atomic_read(&shost->host_eh_scheduled) == 0) ||
+		if ((shost->host_failed == 0 && shost->host_eh_scheduled == 0) ||
 		    shost->host_failed != scsi_host_busy(shost)) {
 			SCSI_LOG_ERROR_RECOVERY(1,
 				shost_printk(KERN_INFO, shost,
@@ -2180,8 +2179,7 @@ int scsi_error_handler(void *data)
 		SCSI_LOG_ERROR_RECOVERY(1,
 			shost_printk(KERN_INFO, shost,
 				     "scsi_eh_%d: waking up %d/%d/%d\n",
-				     shost->host_no,
-				     atomic_read(&shost->host_eh_scheduled),
+				     shost->host_no, shost->host_eh_scheduled,
 				     shost->host_failed,
 				     scsi_host_busy(shost)));
 

drivers/scsi/scsi_lib.c

@@ -348,8 +348,7 @@ static void scsi_dec_host_busy(struct Scsi_Host *shost)
 	atomic_dec(&shost->host_busy);
 	if (unlikely(scsi_host_in_recovery(shost))) {
 		spin_lock_irqsave(shost->host_lock, flags);
-		if (shost->host_failed ||
-		    atomic_read(&shost->host_eh_scheduled))
+		if (shost->host_failed || shost->host_eh_scheduled)
 			scsi_eh_wakeup(shost);
 		spin_unlock_irqrestore(shost->host_lock, flags);
 	}

include/scsi/scsi_host.h

@@ -563,7 +563,7 @@ struct Scsi_Host {
 
 	unsigned int host_failed;	   /* commands that failed.
 					      protected by host_lock */
-	atomic_t host_eh_scheduled;    /* EH scheduled without command */
+	unsigned int host_eh_scheduled;    /* EH scheduled without command */
     
 	unsigned int host_no;  /* Used for IOCTL_GET_IDLUN, /proc/scsi et al. */