[PATCH] shpchp - bugfix: add missing serialization

Current shpchp driver might cause system panic because of lack of
serialization. It can be reproduced very easily by the following
operation.

	# cd /sys/bus/pci/slots/<slot#>
	# while true; do echo 0 > power ; echo 1 > power ; done &
	# while true; do echo 0 > power ; echo 1 > power ; done &

This patch fixes this issue by changing shpchp to get appropreate
semaphore for hot-plug operation.
Signed-off-by: Kenji Kaneshige <kaneshige.kenji@jp.fujitsu.com>
Signed-off-by: Greg Kroah-Hartman <gregkh@suse.de>

drivers/pci/hotplug/shpchp_ctrl.c

@@ -307,15 +307,10 @@ static int board_added(struct slot *p_slot)
 			__FUNCTION__, p_slot->device,
 			ctrl->slot_device_offset, hp_slot);
 
-	/* Wait for exclusive access to hardware */
-	mutex_lock(&ctrl->crit_sect);
-
 	/* Power on slot without connecting to bus */
 	rc = p_slot->hpc_ops->power_on_slot(p_slot);
 	if (rc) {
 		err("%s: Failed to power on slot\n", __FUNCTION__);
-		/* Done with exclusive hardware access */
-		mutex_unlock(&ctrl->crit_sect);
 		return -1;
 	}
 	
@@ -325,14 +320,12 @@ static int board_added(struct slot *p_slot)
 		
 		if ((rc = p_slot->hpc_ops->set_bus_speed_mode(p_slot, PCI_SPEED_33MHz))) {
 			err("%s: Issue of set bus speed mode command failed\n", __FUNCTION__);
-			mutex_unlock(&ctrl->crit_sect);
 			return WRONG_BUS_FREQUENCY;
 		}
 		
 		/* turn on board, blink green LED, turn off Amber LED */
 		if ((rc = p_slot->hpc_ops->slot_enable(p_slot))) {
 			err("%s: Issue of Slot Enable command failed\n", __FUNCTION__);
-			mutex_unlock(&ctrl->crit_sect);
 			return rc;
 		}
 	}
@@ -346,16 +339,12 @@ static int board_added(struct slot *p_slot)
 
 	if (rc  || adapter_speed == PCI_SPEED_UNKNOWN) {
 		err("%s: Can't get adapter speed or bus mode mismatch\n", __FUNCTION__);
-		/* Done with exclusive hardware access */
-		mutex_unlock(&ctrl->crit_sect);
 		return WRONG_BUS_FREQUENCY;
 	}
 
 	rc = p_slot->hpc_ops->get_cur_bus_speed(p_slot, &bus_speed);
 	if (rc || bus_speed == PCI_SPEED_UNKNOWN) {
 		err("%s: Can't get bus operation speed\n", __FUNCTION__);
-		/* Done with exclusive hardware access */
-		mutex_unlock(&ctrl->crit_sect);
 		return WRONG_BUS_FREQUENCY;
 	}
 
@@ -365,9 +354,6 @@ static int board_added(struct slot *p_slot)
 		max_bus_speed = bus_speed;
 	}
 
-	/* Done with exclusive hardware access */
-	mutex_unlock(&ctrl->crit_sect);
-
 	if ((rc  = p_slot->hpc_ops->get_prog_int(p_slot, &pi))) {
 		err("%s: Can't get controller programming interface, set it to 1\n", __FUNCTION__);
 		pi = 1;
@@ -744,29 +730,25 @@ static void interrupt_event_handler(struct controller *ctrl)
 int shpchp_enable_slot (struct slot *p_slot)
 {
 	u8 getstatus = 0;
-	int rc;
+	int rc, retval = -ENODEV;
 
 	/* Check to see if (latch closed, card present, power off) */
 	mutex_lock(&p_slot->ctrl->crit_sect);
 	rc = p_slot->hpc_ops->get_adapter_status(p_slot, &getstatus);
 	if (rc || !getstatus) {
 		info("%s: no adapter on slot(%x)\n", __FUNCTION__, p_slot->number);
-		mutex_unlock(&p_slot->ctrl->crit_sect);
-		return -ENODEV;
+		goto out;
 	}
 	rc = p_slot->hpc_ops->get_latch_status(p_slot, &getstatus);
 	if (rc || getstatus) {
 		info("%s: latch open on slot(%x)\n", __FUNCTION__, p_slot->number);
-		mutex_unlock(&p_slot->ctrl->crit_sect);
-		return -ENODEV;
+		goto out;
 	}
 	rc = p_slot->hpc_ops->get_power_status(p_slot, &getstatus);
 	if (rc || getstatus) {
 		info("%s: already enabled on slot(%x)\n", __FUNCTION__, p_slot->number);
-		mutex_unlock(&p_slot->ctrl->crit_sect);
-		return -ENODEV;
+		goto out;
 	}
-	mutex_unlock(&p_slot->ctrl->crit_sect);
 
 	p_slot->is_a_board = 1;
 
@@ -781,27 +763,29 @@ int shpchp_enable_slot (struct slot *p_slot)
 	     && p_slot->ctrl->num_slots == 1) {
 		/* handle amd pogo errata; this must be done before enable  */
 		amd_pogo_errata_save_misc_reg(p_slot);
-		rc = board_added(p_slot);
+		retval = board_added(p_slot);
 		/* handle amd pogo errata; this must be done after enable  */
 		amd_pogo_errata_restore_misc_reg(p_slot);
 	} else
-		rc = board_added(p_slot);
+		retval = board_added(p_slot);
 
-	if (rc) {
+	if (retval) {
 		p_slot->hpc_ops->get_adapter_status(p_slot,
 				&(p_slot->presence_save));
 		p_slot->hpc_ops->get_latch_status(p_slot, &getstatus);
 	}
 
 	update_slot_info(p_slot);
-	return rc;
+ out:
+	mutex_unlock(&p_slot->ctrl->crit_sect);
+	return retval;
 }
 
 
 int shpchp_disable_slot (struct slot *p_slot)
 {
 	u8 getstatus = 0;
-	int ret = 0;
+	int rc, retval = -ENODEV;
 
 	if (!p_slot->ctrl)
 		return -ENODEV;
@@ -809,28 +793,26 @@ int shpchp_disable_slot (struct slot *p_slot)
 	/* Check to see if (latch closed, card present, power on) */
 	mutex_lock(&p_slot->ctrl->crit_sect);
 
-	ret = p_slot->hpc_ops->get_adapter_status(p_slot, &getstatus);
-	if (ret || !getstatus) {
+	rc = p_slot->hpc_ops->get_adapter_status(p_slot, &getstatus);
+	if (rc || !getstatus) {
 		info("%s: no adapter on slot(%x)\n", __FUNCTION__, p_slot->number);
-		mutex_unlock(&p_slot->ctrl->crit_sect);
-		return -ENODEV;
+		goto out;
 	}
-	ret = p_slot->hpc_ops->get_latch_status(p_slot, &getstatus);
-	if (ret || getstatus) {
+	rc = p_slot->hpc_ops->get_latch_status(p_slot, &getstatus);
+	if (rc || getstatus) {
 		info("%s: latch open on slot(%x)\n", __FUNCTION__, p_slot->number);
-		mutex_unlock(&p_slot->ctrl->crit_sect);
-		return -ENODEV;
+		goto out;
 	}
-	ret = p_slot->hpc_ops->get_power_status(p_slot, &getstatus);
-	if (ret || !getstatus) {
+	rc = p_slot->hpc_ops->get_power_status(p_slot, &getstatus);
+	if (rc || !getstatus) {
 		info("%s: already disabled slot(%x)\n", __FUNCTION__, p_slot->number);
-		mutex_unlock(&p_slot->ctrl->crit_sect);
-		return -ENODEV;
+		goto out;
 	}
-	mutex_unlock(&p_slot->ctrl->crit_sect);
 
-	ret = remove_board(p_slot);
+	retval = remove_board(p_slot);
 	update_slot_info(p_slot);
-	return ret;
+ out:
+	mutex_unlock(&p_slot->ctrl->crit_sect);
+	return retval;
 }