[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: Gerald Schaefer <gerald.schaefer@de.ibm.com>
Signed-off-by: Martin Schwidefsky <schwidefsky@de.ibm.com>

2 files changed, 17 insertions, 17 deletions

diff --git a/arch/s390/appldata/appldata_base.c b/arch/s390/appldata/appldata_base.c
index aeb3cff95f63..1dfc7100c7ee 100644
--- a/arch/s390/appldata/appldata_base.c
+++ b/arch/s390/appldata/appldata_base.c
@@ -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);
 }
diff --git a/arch/s390/appldata/appldata_mem.c b/arch/s390/appldata/appldata_mem.c
index 3ed56b7d1b2f..4188cbe63a54 100644
--- a/arch/s390/appldata/appldata_mem.c
+++ b/arch/s390/appldata/appldata_mem.c
@@ -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];