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Commit cf352ce0 authored by Ralph Wuerthner's avatar Ralph Wuerthner Committed by Martin Schwidefsky
Browse files

[S390] zcrypt: fix possible dead lock in AP bus module 



AP bus module uses bus_for_each_dev() in software interrupt context to
poll for completed requests which might cause dead locks. Solution: use
private AP device list for polling in software interrupt context.

Signed-off-by: default avatarRalph Wuerthner <rwuerthn@de.ibm.com>
Signed-off-by: default avatarMartin Schwidefsky <schwidefsky@de.ibm.com>
parent fb1c1719

drivers/s390/crypto/ap_bus.c

+23 −7
Original line number Diff line number Diff line
@@ -65,6 +65,8 @@ module_param_named(poll_thread, ap_thread_flag, int, 0000); 
MODULE_PARM_DESC(poll_thread, "Turn on/off poll thread, default is 1 (on).");



static struct device *ap_root_device = NULL;

static DEFINE_SPINLOCK(ap_device_lock);

static LIST_HEAD(ap_device_list);



/**

 * Workqueue & timer for bus rescan.
@@ -457,6 +459,9 @@ static int ap_device_probe(struct device *dev) 
	int rc;



	ap_dev->drv = ap_drv;

	spin_lock_bh(&ap_device_lock);

	list_add(&ap_dev->list, &ap_device_list);

	spin_unlock_bh(&ap_device_lock);

	rc = ap_drv->probe ? ap_drv->probe(ap_dev) : -ENODEV;

	return rc;

}
@@ -497,6 +502,9 @@ static int ap_device_remove(struct device *dev) 
	ap_flush_queue(ap_dev);

	if (ap_drv->remove)

		ap_drv->remove(ap_dev);

	spin_lock_bh(&ap_device_lock);

	list_del_init(&ap_dev->list);

	spin_unlock_bh(&ap_device_lock);

	return 0;

}
@@ -772,6 +780,7 @@ static void ap_scan_bus(struct work_struct *unused) 
		spin_lock_init(&ap_dev->lock);

		INIT_LIST_HEAD(&ap_dev->pendingq);

		INIT_LIST_HEAD(&ap_dev->requestq);

		INIT_LIST_HEAD(&ap_dev->list);

		if (device_type == 0)

			ap_probe_device_type(ap_dev);

		else
@@ -1033,14 +1042,13 @@ static void ap_poll_timeout(unsigned long unused) 
 * polling until bit 2^0 of the control flags is not set. If bit 2^1

 * of the control flags has been set arm the poll timer.

 */

static int __ap_poll_all(struct device *dev, void *data)

static int __ap_poll_all(struct ap_device *ap_dev, unsigned long *flags)

{

	struct ap_device *ap_dev = to_ap_dev(dev);

	int rc;



	spin_lock(&ap_dev->lock);

	if (!ap_dev->unregistered) {

		rc = ap_poll_queue(to_ap_dev(dev), (unsigned long *) data);

		rc = ap_poll_queue(ap_dev, flags);

		if (rc)

			ap_dev->unregistered = 1;

	} else
@@ -1054,10 +1062,15 @@ static int __ap_poll_all(struct device *dev, void *data) 
static void ap_poll_all(unsigned long dummy)

{

	unsigned long flags;

	struct ap_device *ap_dev;



	do {

		flags = 0;

		bus_for_each_dev(&ap_bus_type, NULL, &flags, __ap_poll_all);

		spin_lock(&ap_device_lock);

		list_for_each_entry(ap_dev, &ap_device_list, list) {

			__ap_poll_all(ap_dev, &flags);

		}

		spin_unlock(&ap_device_lock);

	} while (flags & 1);

	if (flags & 2)

		ap_schedule_poll_timer();
@@ -1075,6 +1088,7 @@ static int ap_poll_thread(void *data) 
	DECLARE_WAITQUEUE(wait, current);

	unsigned long flags;

	int requests;

	struct ap_device *ap_dev;



	set_user_nice(current, 19);

	while (1) {
@@ -1092,10 +1106,12 @@ static int ap_poll_thread(void *data) 
		set_current_state(TASK_RUNNING);

		remove_wait_queue(&ap_poll_wait, &wait);



		local_bh_disable();

		flags = 0;

		bus_for_each_dev(&ap_bus_type, NULL, &flags, __ap_poll_all);

		local_bh_enable();

		spin_lock_bh(&ap_device_lock);

		list_for_each_entry(ap_dev, &ap_device_list, list) {

			__ap_poll_all(ap_dev, &flags);

		}

		spin_unlock_bh(&ap_device_lock);

	}

	set_current_state(TASK_RUNNING);

	remove_wait_queue(&ap_poll_wait, &wait);

drivers/s390/crypto/ap_bus.h

+1 −0
Original line number Diff line number Diff line
@@ -106,6 +106,7 @@ struct ap_device { 
	struct device device;

	struct ap_driver *drv;		/* Pointer to AP device driver. */

	spinlock_t lock;		/* Per device lock. */

	struct list_head list;		/* private list of all AP devices. */



	ap_qid_t qid;			/* AP queue id. */

	int queue_depth;		/* AP queue depth.*/