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Commit b1ad171e authored by Gerald Schaefer's avatar Gerald Schaefer Committed by Martin Schwidefsky
Browse files

[S390] appldata: avoid deadlock with appldata_mem 



The appldata_ops callbacks are called with a spin_lock held. But the
appldata_mem callback then calls all_vm_events(), which calls
get_online_cpus(), which might sleep. This possible deadlock is fixed
by using a mutex instead of a spin_lock.

Signed-off-by: default avatarGerald Schaefer <gerald.schaefer@de.ibm.com>
Signed-off-by: default avatarMartin Schwidefsky <schwidefsky@de.ibm.com>
parent 3bd5f3ef

arch/s390/appldata/appldata_base.c

+16 −16
Original line number Diff line number Diff line
@@ -98,7 +98,7 @@ static DECLARE_WORK(appldata_work, appldata_work_fn); 
/*

 * Ops list

 */

static DEFINE_SPINLOCK(appldata_ops_lock);

static DEFINE_MUTEX(appldata_ops_mutex);

static LIST_HEAD(appldata_ops_list);
@@ -129,14 +129,14 @@ static void appldata_work_fn(struct work_struct *work) 


	i = 0;

	get_online_cpus();

	spin_lock(&appldata_ops_lock);

	mutex_lock(&appldata_ops_mutex);

	list_for_each(lh, &appldata_ops_list) {

		ops = list_entry(lh, struct appldata_ops, list);

		if (ops->active == 1) {

			ops->callback(ops->data);

		}

	}

	spin_unlock(&appldata_ops_lock);

	mutex_unlock(&appldata_ops_mutex);

	put_online_cpus();

}
@@ -338,7 +338,7 @@ appldata_generic_handler(ctl_table *ctl, int write, struct file *filp, 
	struct list_head *lh;



	found = 0;

	spin_lock(&appldata_ops_lock);

	mutex_lock(&appldata_ops_mutex);

	list_for_each(lh, &appldata_ops_list) {

		tmp_ops = list_entry(lh, struct appldata_ops, list);

		if (&tmp_ops->ctl_table[2] == ctl) {
@@ -346,15 +346,15 @@ appldata_generic_handler(ctl_table *ctl, int write, struct file *filp, 
		}

	}

	if (!found) {

		spin_unlock(&appldata_ops_lock);

		mutex_unlock(&appldata_ops_mutex);

		return -ENODEV;

	}

	ops = ctl->data;

	if (!try_module_get(ops->owner)) {	// protect this function

		spin_unlock(&appldata_ops_lock);

		mutex_unlock(&appldata_ops_mutex);

		return -ENODEV;

	}

	spin_unlock(&appldata_ops_lock);

	mutex_unlock(&appldata_ops_mutex);



	if (!*lenp || *ppos) {

		*lenp = 0;
@@ -378,11 +378,11 @@ appldata_generic_handler(ctl_table *ctl, int write, struct file *filp, 
		return -EFAULT;

	}



	spin_lock(&appldata_ops_lock);

	mutex_lock(&appldata_ops_mutex);

	if ((buf[0] == '1') && (ops->active == 0)) {

		// protect work queue callback

		if (!try_module_get(ops->owner)) {

			spin_unlock(&appldata_ops_lock);

			mutex_unlock(&appldata_ops_mutex);

			module_put(ops->owner);

			return -ENODEV;

		}
@@ -407,7 +407,7 @@ appldata_generic_handler(ctl_table *ctl, int write, struct file *filp, 
			       "failed with rc=%d\n", ops->name, rc);

		module_put(ops->owner);

	}

	spin_unlock(&appldata_ops_lock);

	mutex_unlock(&appldata_ops_mutex);

out:

	*lenp = len;

	*ppos += len;
@@ -433,9 +433,9 @@ int appldata_register_ops(struct appldata_ops *ops) 
	if (!ops->ctl_table)

		return -ENOMEM;



	spin_lock(&appldata_ops_lock);

	mutex_lock(&appldata_ops_mutex);

	list_add(&ops->list, &appldata_ops_list);

	spin_unlock(&appldata_ops_lock);

	mutex_unlock(&appldata_ops_mutex);



	ops->ctl_table[0].procname = appldata_proc_name;

	ops->ctl_table[0].maxlen   = 0;
@@ -452,9 +452,9 @@ int appldata_register_ops(struct appldata_ops *ops) 
		goto out;

	return 0;

out:

	spin_lock(&appldata_ops_lock);

	mutex_lock(&appldata_ops_mutex);

	list_del(&ops->list);

	spin_unlock(&appldata_ops_lock);

	mutex_unlock(&appldata_ops_mutex);

	kfree(ops->ctl_table);

	return -ENOMEM;

}
@@ -466,9 +466,9 @@ out: 
 */

void appldata_unregister_ops(struct appldata_ops *ops)

{

	spin_lock(&appldata_ops_lock);

	mutex_lock(&appldata_ops_mutex);

	list_del(&ops->list);

	spin_unlock(&appldata_ops_lock);

	mutex_unlock(&appldata_ops_mutex);

	unregister_sysctl_table(ops->sysctl_header);

	kfree(ops->ctl_table);

}

arch/s390/appldata/appldata_mem.c

+1 −1
Original line number Diff line number Diff line
@@ -78,7 +78,7 @@ static void appldata_get_mem_data(void *data) 
{

	/*

	 * don't put large structures on the stack, we are

	 * serialized through the appldata_ops_lock and can use static

	 * serialized through the appldata_ops_mutex and can use static

	 */

	static struct sysinfo val;

	unsigned long ev[NR_VM_EVENT_ITEMS];