diff --git a/drivers/scsi/libata-scsi.c b/drivers/scsi/libata-scsi.c
index 2d328b3af067..3a4f40b251fb 100644
--- a/drivers/scsi/libata-scsi.c
+++ b/drivers/scsi/libata-scsi.c
@@ -735,6 +735,11 @@ int ata_scsi_error(struct Scsi_Host *host)
 
 	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 @@ int ata_scsi_error(struct Scsi_Host *host)
 
 	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;
 }
diff --git a/include/linux/libata.h b/include/linux/libata.h
index 474cdfa35d1e..55176df403a5 100644
--- a/include/linux/libata.h
+++ b/include/linux/libata.h
@@ -162,6 +162,8 @@ enum {
 	ATA_FLAG_PIO_LBA48	= (1 << 13), /* Host DMA engine is LBA28 only */
 	ATA_FLAG_IRQ_MASK	= (1 << 14), /* Mask IRQ in PIO xfers */
 
+	ATA_FLAG_IN_EH		= (1 << 15), /* EH in progress */
+
 	ATA_QCFLAG_ACTIVE	= (1 << 1), /* cmd not yet ack'd to scsi lyer */
 	ATA_QCFLAG_SG		= (1 << 3), /* have s/g table? */
 	ATA_QCFLAG_SINGLE	= (1 << 4), /* no s/g, just a single buffer */