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authorMartin Schwidefsky <schwidefsky@de.ibm.com>2007-04-28 23:03:59 -0700
committerDavid S. Miller <davem@davemloft.net>2007-04-28 23:03:59 -0700
commit04b090d50c88ac8e5ec9c2e985bb65bd153893aa (patch)
tree065b815f238796bcd5523c8620d9166ad9b573f2 /net/iucv
parentd0772b70faaf8e9f2013b6c4273d94d5eac8047a (diff)
[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: Frank Pavlic <fpavlic@de.ibm.com> Signed-off-by: Martin Schwidefsky <schwidefsky@de.ibm.com> Signed-off-by: David S. Miller <davem@davemloft.net>
Diffstat (limited to 'net/iucv')
-rw-r--r--net/iucv/iucv.c205
1 files changed, 132 insertions, 73 deletions
diff --git a/net/iucv/iucv.c b/net/iucv/iucv.c
index 60f293842a39..903bdb6eaaa1 100644
--- a/net/iucv/iucv.c
+++ b/net/iucv/iucv.c
@@ -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())
- spin_lock_bh(&iucv_table_lock);
+ 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();
+ spin_unlock_bh(&iucv_table_lock);
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_work_lock);
- while (!list_empty(&iucv_work_queue)) {
- p = list_entry(iucv_work_queue.next, struct iucv_work, list);
+ spin_lock_irq(&iucv_queue_lock);
+ list_splice_init(&iucv_task_queue, &task_queue);
+ spin_unlock_irq(&iucv_queue_lock);
+
+ 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) {
@@ -1498,16 +1548,23 @@ 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);
- list_add_tail(&work->list, &iucv_work_queue);
- spin_unlock(&iucv_work_lock);
- tasklet_schedule(&iucv_tasklet);
+ spin_lock(&iucv_queue_lock);
+ if (p->iptype == 0x01) {
+ /* Path pending interrupt. */
+ list_add_tail(&work->list, &iucv_work_queue);
+ 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);
}
/**
@@ -1577,12 +1634,14 @@ out:
*/
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);

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