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Subject[patch 2/6] appldata: avoid deadlock with appldata_mem
From: Gerald Schaefer <gerald.schaefer@de.ibm.com>

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>
---
arch/s390/appldata/appldata_base.c | 32 ++++++++++++++++----------------
arch/s390/appldata/appldata_mem.c | 2 +-
2 files changed, 17 insertions(+), 17 deletions(-)
Index: quilt-2.6/arch/s390/appldata/appldata_base.c
===================================================================
--- quilt-2.6.orig/arch/s390/appldata/appldata_base.c
+++ quilt-2.6/arch/s390/appldata/appldata_base.c
@@ -98,7 +98,7 @@ static DECLARE_WORK(appldata_work, appld
/*
* 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

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,
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,
}
}
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,
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,
"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 appldat
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 appldat
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);
}
Index: quilt-2.6/arch/s390/appldata/appldata_mem.c
===================================================================
--- quilt-2.6.orig/arch/s390/appldata/appldata_mem.c
+++ quilt-2.6/arch/s390/appldata/appldata_mem.c
@@ -78,7 +78,7 @@ static void appldata_get_mem_data(void *
{
/*
* 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];
--
blue skies,
Martin.

"Reality continues to ruin my life." - Calvin.



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