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Commit 04b090d5 authored by Martin Schwidefsky's avatar Martin Schwidefsky Committed by David S. Miller
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[AF_IUCV/IUCV]: smp_call_function deadlock 



Calling smp_call_function can lead to a deadlock if it is called
from tasklet context. 
Fixing this deadlock requires to move the smp_call_function from the
tasklet context to a work queue. To do that queue the path pending
interrupts to a separate list and move the path cleanup out of
iucv_path_sever to iucv_path_connect and iucv_path_pending.
This creates a new requirement for iucv_path_connect: it may not be
called from tasklet context anymore. 
Also fixed compile problem for CONFIG_HOTPLUG_CPU=n and
another one when walking the cpu_online mask. When doing this, 
we must disable cpu hotplug.

Signed-off-by: default avatarFrank Pavlic <fpavlic@de.ibm.com>
Signed-off-by: default avatarMartin Schwidefsky <schwidefsky@de.ibm.com>
Signed-off-by: default avatarDavid S. Miller <davem@davemloft.net>
parent d0772b70

include/net/iucv/iucv.h

+1 −1
Original line number Diff line number Diff line
@@ -16,7 +16,7 @@ 
 * completed a register, it can exploit the other functions.

 * For furthur reference on all IUCV functionality, refer to the

 * CP Programming Services book, also available on the web thru

 * www.ibm.com/s390/vm/pubs, manual # SC24-5760

 * www.vm.ibm.com/pubs, manual # SC24-6084

 *

 * Definition of Return Codes

 * - All positive return codes including zero are reflected back

net/iucv/iucv.c

+132 −73
Original line number Diff line number Diff line
@@ -90,20 +90,43 @@ struct iucv_irq_data { 
	u32 res2[8];

};



struct iucv_work {

struct iucv_irq_list {

	struct list_head list;

	struct iucv_irq_data data;

};



static LIST_HEAD(iucv_work_queue);

static DEFINE_SPINLOCK(iucv_work_lock);



static struct iucv_irq_data *iucv_irq_data;

static cpumask_t iucv_buffer_cpumask = CPU_MASK_NONE;

static cpumask_t iucv_irq_cpumask = CPU_MASK_NONE;



static void iucv_tasklet_handler(unsigned long);

static DECLARE_TASKLET(iucv_tasklet, iucv_tasklet_handler,0);

/*

 * Queue of interrupt buffers lock for delivery via the tasklet

 * (fast but can't call smp_call_function).

 */

static LIST_HEAD(iucv_task_queue);



/*

 * The tasklet for fast delivery of iucv interrupts.

 */

static void iucv_tasklet_fn(unsigned long);

static DECLARE_TASKLET(iucv_tasklet, iucv_tasklet_fn,0);



/*

 * Queue of interrupt buffers for delivery via a work queue

 * (slower but can call smp_call_function).

 */

static LIST_HEAD(iucv_work_queue);



/*

 * The work element to deliver path pending interrupts.

 */

static void iucv_work_fn(struct work_struct *work);

static DECLARE_WORK(iucv_work, iucv_work_fn);



/*

 * Spinlock protecting task and work queue.

 */

static DEFINE_SPINLOCK(iucv_queue_lock);



enum iucv_command_codes {

	IUCV_QUERY = 0,
@@ -147,10 +170,10 @@ static unsigned long iucv_max_pathid; 
static DEFINE_SPINLOCK(iucv_table_lock);



/*

 * iucv_tasklet_cpu: contains the number of the cpu executing the tasklet.

 * Needed for iucv_path_sever called from tasklet.

 * iucv_active_cpu: contains the number of the cpu executing the tasklet

 * or the work handler. Needed for iucv_path_sever called from tasklet.

 */

static int iucv_tasklet_cpu = -1;

static int iucv_active_cpu = -1;



/*

 * Mutex and wait queue for iucv_register/iucv_unregister.
@@ -449,17 +472,19 @@ static void iucv_setmask_mp(void) 
{

	int cpu;



	preempt_disable();

	for_each_online_cpu(cpu)

		/* Enable all cpus with a declared buffer. */

		if (cpu_isset(cpu, iucv_buffer_cpumask) &&

		    !cpu_isset(cpu, iucv_irq_cpumask))

			smp_call_function_on(iucv_allow_cpu, NULL, 0, 1, cpu);

	preempt_enable();

}



/**

 * iucv_setmask_up

 *

 * Allow iucv interrupts on a single cpus.

 * Allow iucv interrupts on a single cpu.

 */

static void iucv_setmask_up(void)

{
@@ -493,8 +518,10 @@ static int iucv_enable(void) 
		goto out;

	/* Declare per cpu buffers. */

	rc = -EIO;

	preempt_disable();

	for_each_online_cpu(cpu)

		smp_call_function_on(iucv_declare_cpu, NULL, 0, 1, cpu);

	preempt_enable();

	if (cpus_empty(iucv_buffer_cpumask))

		/* No cpu could declare an iucv buffer. */

		goto out_path;
@@ -584,48 +611,49 @@ static int iucv_sever_pathid(u16 pathid, u8 userdata[16]) 
	return iucv_call_b2f0(IUCV_SEVER, parm);

}



#ifdef CONFIG_SMP

/**

 * __iucv_cleanup_pathid

 * __iucv_cleanup_queue

 * @dummy: unused dummy argument

 *

 * Nop function called via smp_call_function to force work items from

 * pending external iucv interrupts to the work queue.

 */

static void __iucv_cleanup_pathid(void *dummy)

static void __iucv_cleanup_queue(void *dummy)

{

}

#endif



/**

 * iucv_cleanup_pathid

 * @pathid: 16 bit pathid

 * iucv_cleanup_queue

 *

 * Function called after a path has been severed to find all remaining

 * work items for the now stale pathid. The caller needs to hold the

 * iucv_table_lock.

 */

static void iucv_cleanup_pathid(u16 pathid)

static void iucv_cleanup_queue(void)

{

	struct iucv_work *p, *n;

	struct iucv_irq_list *p, *n;



	/*

	 * Path is severed, the pathid can be reused immediatly on

	 * a iucv connect or a connection pending interrupt.

	 * iucv_path_connect and connection pending interrupt will

	 * wait until the iucv_table_lock is released before the

	 * recycled pathid enters the system.

	 * Force remaining interrupts to the work queue, then

	 * scan the work queue for items of this path.

	 * When a path is severed, the pathid can be reused immediatly

	 * on a iucv connect or a connection pending interrupt. Remove

	 * all entries from the task queue that refer to a stale pathid

	 * (iucv_path_table[ix] == NULL). Only then do the iucv connect

	 * or deliver the connection pending interrupt. To get all the

	 * pending interrupts force them to the work queue by calling

	 * an empty function on all cpus.

	 */

	smp_call_function(__iucv_cleanup_pathid, NULL, 0, 1);

	spin_lock_irq(&iucv_work_lock);

	list_for_each_entry_safe(p, n, &iucv_work_queue, list) {

		/* Remove work items for pathid except connection pending */

		if (p->data.ippathid == pathid && p->data.iptype != 0x01) {

	smp_call_function(__iucv_cleanup_queue, NULL, 0, 1);

	spin_lock_irq(&iucv_queue_lock);

	list_for_each_entry_safe(p, n, &iucv_task_queue, list) {

		/* Remove stale work items from the task queue. */

		if (iucv_path_table[p->data.ippathid] == NULL) {

			list_del(&p->list);

			kfree(p);

		}

	}

	spin_unlock_irq(&iucv_work_lock);

	spin_unlock_irq(&iucv_queue_lock);

}



/**
@@ -684,7 +712,6 @@ void iucv_unregister(struct iucv_handler *handler, int smp) 
		iucv_sever_pathid(p->pathid, NULL);

		iucv_path_table[p->pathid] = NULL;

		list_del(&p->list);

		iucv_cleanup_pathid(p->pathid);

		iucv_path_free(p);

	}

	spin_unlock_bh(&iucv_table_lock);
@@ -757,9 +784,9 @@ int iucv_path_connect(struct iucv_path *path, struct iucv_handler *handler, 
	union iucv_param *parm;

	int rc;



	preempt_disable();

	if (iucv_tasklet_cpu != smp_processor_id())

	BUG_ON(in_atomic());

	spin_lock_bh(&iucv_table_lock);

	iucv_cleanup_queue();

	parm = percpu_ptr(iucv_param, smp_processor_id());

	memset(parm, 0, sizeof(union iucv_param));

	parm->ctrl.ipmsglim = path->msglim;
@@ -794,9 +821,7 @@ int iucv_path_connect(struct iucv_path *path, struct iucv_handler *handler, 
			rc = -EIO;

		}

	}

	if (iucv_tasklet_cpu != smp_processor_id())

	spin_unlock_bh(&iucv_table_lock);

	preempt_enable();

	return rc;

}
@@ -867,15 +892,14 @@ int iucv_path_sever(struct iucv_path *path, u8 userdata[16]) 




	preempt_disable();

	if (iucv_tasklet_cpu != smp_processor_id())

	if (iucv_active_cpu != smp_processor_id())

		spin_lock_bh(&iucv_table_lock);

	rc = iucv_sever_pathid(path->pathid, userdata);

	if (!rc) {

		iucv_path_table[path->pathid] = NULL;

		list_del_init(&path->list);

		iucv_cleanup_pathid(path->pathid);

	}

	if (iucv_tasklet_cpu != smp_processor_id())

	if (iucv_active_cpu != smp_processor_id())

		spin_unlock_bh(&iucv_table_lock);

	preempt_enable();

	return rc;
@@ -1244,8 +1268,7 @@ static void iucv_path_complete(struct iucv_irq_data *data) 
	struct iucv_path_complete *ipc = (void *) data;

	struct iucv_path *path = iucv_path_table[ipc->ippathid];



	BUG_ON(!path || !path->handler);

	if (path->handler->path_complete)

	if (path && path->handler && path->handler->path_complete)

		path->handler->path_complete(path, ipc->ipuser);

}
@@ -1273,14 +1296,14 @@ static void iucv_path_severed(struct iucv_irq_data *data) 
	struct iucv_path_severed *ips = (void *) data;

	struct iucv_path *path = iucv_path_table[ips->ippathid];



	BUG_ON(!path || !path->handler);

	if (!path || !path->handler)	/* Already severed */

		return;

	if (path->handler->path_severed)

		path->handler->path_severed(path, ips->ipuser);

	else {

		iucv_sever_pathid(path->pathid, NULL);

		iucv_path_table[path->pathid] = NULL;

		list_del_init(&path->list);

		iucv_cleanup_pathid(path->pathid);

		iucv_path_free(path);

	}

}
@@ -1309,8 +1332,7 @@ static void iucv_path_quiesced(struct iucv_irq_data *data) 
	struct iucv_path_quiesced *ipq = (void *) data;

	struct iucv_path *path = iucv_path_table[ipq->ippathid];



	BUG_ON(!path || !path->handler);

	if (path->handler->path_quiesced)

	if (path && path->handler && path->handler->path_quiesced)

		path->handler->path_quiesced(path, ipq->ipuser);

}
@@ -1338,8 +1360,7 @@ static void iucv_path_resumed(struct iucv_irq_data *data) 
	struct iucv_path_resumed *ipr = (void *) data;

	struct iucv_path *path = iucv_path_table[ipr->ippathid];



	BUG_ON(!path || !path->handler);

	if (path->handler->path_resumed)

	if (path && path->handler && path->handler->path_resumed)

		path->handler->path_resumed(path, ipr->ipuser);

}
@@ -1371,8 +1392,7 @@ static void iucv_message_complete(struct iucv_irq_data *data) 
	struct iucv_path *path = iucv_path_table[imc->ippathid];

	struct iucv_message msg;



	BUG_ON(!path || !path->handler);

	if (path->handler->message_complete) {

	if (path && path->handler && path->handler->message_complete) {

		msg.flags = imc->ipflags1;

		msg.id = imc->ipmsgid;

		msg.audit = imc->ipaudit;
@@ -1417,8 +1437,7 @@ static void iucv_message_pending(struct iucv_irq_data *data) 
	struct iucv_path *path = iucv_path_table[imp->ippathid];

	struct iucv_message msg;



	BUG_ON(!path || !path->handler);

	if (path->handler->message_pending) {

	if (path && path->handler && path->handler->message_pending) {

		msg.flags = imp->ipflags1;

		msg.id = imp->ipmsgid;

		msg.class = imp->iptrgcls;
@@ -1433,17 +1452,16 @@ static void iucv_message_pending(struct iucv_irq_data *data) 
}



/**

 * iucv_tasklet_handler:

 * iucv_tasklet_fn:

 *

 * This tasklet loops over the queue of irq buffers created by

 * iucv_external_interrupt, calls the appropriate action handler

 * and then frees the buffer.

 */

static void iucv_tasklet_handler(unsigned long ignored)

static void iucv_tasklet_fn(unsigned long ignored)

{

	typedef void iucv_irq_fn(struct iucv_irq_data *);

	static iucv_irq_fn *irq_fn[] = {

		[0x01] = iucv_path_pending,

		[0x02] = iucv_path_complete,

		[0x03] = iucv_path_severed,

		[0x04] = iucv_path_quiesced,
@@ -1453,38 +1471,70 @@ static void iucv_tasklet_handler(unsigned long ignored) 
		[0x08] = iucv_message_pending,

		[0x09] = iucv_message_pending,

	};

	struct iucv_work *p;

	struct list_head task_queue = LIST_HEAD_INIT(task_queue);

	struct iucv_irq_list *p, *n;



	/* Serialize tasklet, iucv_path_sever and iucv_path_connect. */

	spin_lock(&iucv_table_lock);

	iucv_tasklet_cpu = smp_processor_id();

	iucv_active_cpu = smp_processor_id();



	spin_lock_irq(&iucv_queue_lock);

	list_splice_init(&iucv_task_queue, &task_queue);

	spin_unlock_irq(&iucv_queue_lock);



	spin_lock_irq(&iucv_work_lock);

	while (!list_empty(&iucv_work_queue)) {

		p = list_entry(iucv_work_queue.next, struct iucv_work, list);

	list_for_each_entry_safe(p, n, &task_queue, list) {

		list_del_init(&p->list);

		spin_unlock_irq(&iucv_work_lock);

		irq_fn[p->data.iptype](&p->data);

		kfree(p);

		spin_lock_irq(&iucv_work_lock);

	}

	spin_unlock_irq(&iucv_work_lock);



	iucv_tasklet_cpu = -1;

	iucv_active_cpu = -1;

	spin_unlock(&iucv_table_lock);

}



/**

 * iucv_work_fn:

 *

 * This work function loops over the queue of path pending irq blocks

 * created by iucv_external_interrupt, calls the appropriate action

 * handler and then frees the buffer.

 */

static void iucv_work_fn(struct work_struct *work)

{

	typedef void iucv_irq_fn(struct iucv_irq_data *);

	struct list_head work_queue = LIST_HEAD_INIT(work_queue);

	struct iucv_irq_list *p, *n;



	/* Serialize tasklet, iucv_path_sever and iucv_path_connect. */

	spin_lock_bh(&iucv_table_lock);

	iucv_active_cpu = smp_processor_id();



	spin_lock_irq(&iucv_queue_lock);

	list_splice_init(&iucv_work_queue, &work_queue);

	spin_unlock_irq(&iucv_queue_lock);



	iucv_cleanup_queue();

	list_for_each_entry_safe(p, n, &work_queue, list) {

		list_del_init(&p->list);

		iucv_path_pending(&p->data);

		kfree(p);

	}



	iucv_active_cpu = -1;

	spin_unlock_bh(&iucv_table_lock);

}



/**

 * iucv_external_interrupt

 * @code: irq code

 *

 * Handles external interrupts coming in from CP.

 * Places the interrupt buffer on a queue and schedules iucv_tasklet_handler().

 * Places the interrupt buffer on a queue and schedules iucv_tasklet_fn().

 */

static void iucv_external_interrupt(u16 code)

{

	struct iucv_irq_data *p;

	struct iucv_work *work;

	struct iucv_irq_list *work;



	p = percpu_ptr(iucv_irq_data, smp_processor_id());

	if (p->ippathid >= iucv_max_pathid) {
@@ -1498,17 +1548,24 @@ static void iucv_external_interrupt(u16 code) 
		printk(KERN_ERR "iucv_do_int: unknown iucv interrupt\n");

		return;

	}

	work = kmalloc(sizeof(struct iucv_work), GFP_ATOMIC);

	work = kmalloc(sizeof(struct iucv_irq_list), GFP_ATOMIC);

	if (!work) {

		printk(KERN_WARNING "iucv_external_interrupt: out of memory\n");

		return;

	}

	memcpy(&work->data, p, sizeof(work->data));

	spin_lock(&iucv_work_lock);

	spin_lock(&iucv_queue_lock);

	if (p->iptype == 0x01) {

		/* Path pending interrupt. */

		list_add_tail(&work->list, &iucv_work_queue);

	spin_unlock(&iucv_work_lock);

		schedule_work(&iucv_work);

	} else {

		/* The other interrupts. */

		list_add_tail(&work->list, &iucv_task_queue);

		tasklet_schedule(&iucv_tasklet);

	}

	spin_unlock(&iucv_queue_lock);

}



/**

 * iucv_init
@@ -1577,12 +1634,14 @@ static int iucv_init(void) 
 */

static void iucv_exit(void)

{

	struct iucv_work *p, *n;

	struct iucv_irq_list *p, *n;



	spin_lock_irq(&iucv_work_lock);

	spin_lock_irq(&iucv_queue_lock);

	list_for_each_entry_safe(p, n, &iucv_task_queue, list)

		kfree(p);

	list_for_each_entry_safe(p, n, &iucv_work_queue, list)

		kfree(p);

	spin_unlock_irq(&iucv_work_lock);

	spin_unlock_irq(&iucv_queue_lock);

	unregister_hotcpu_notifier(&iucv_cpu_notifier);

	percpu_free(iucv_param);

	percpu_free(iucv_irq_data);