diff --git a/drivers/scsi/libata-scsi.c b/drivers/scsi/libata-scsi.c
index 2d328b3..3a4f40b 100644
--- a/drivers/scsi/libata-scsi.c
+++ b/drivers/scsi/libata-scsi.c
@@ -735,6 +735,11 @@
 
 	DPRINTK("ENTER\n");
 
+	spin_lock_irqsave(&ap->host_set->lock, flags);
+	assert(!(ap->flags & ATA_FLAG_IN_EH));
+	ap->flags |= ATA_FLAG_IN_EH;
+	spin_unlock_irqrestore(&ap->host_set->lock, flags);
+
 	ap = (struct ata_port *) &host->hostdata[0];
 	ap->ops->eng_timeout(ap);
 
@@ -742,6 +747,10 @@
 
 	scsi_eh_flush_done_q(&ap->eh_done_q);
 
+	spin_lock_irqsave(&ap->host_set->lock, flags);
+	ap->flags &= ~ATA_FLAG_IN_EH;
+	spin_unlock_irqrestore(&ap->host_set->lock, flags);
+
 	DPRINTK("EXIT\n");
 	return 0;
 }