workqueue: debug flushing deadlocks with lockdep
In the following scenario:
code path 1:
my_function() -> lock(L1); ...; flush_workqueue(); ...
code path 2:
run_workqueue() -> my_work() -> ...; lock(L1); ...
you can get a deadlock when my_work() is queued or running
but my_function() has acquired L1 already.
This patch adds a pseudo-lock to each workqueue to make lockdep
warn about this scenario.
[akpm@linux-foundation.org: coding-style fixes]
Signed-off-by: Johannes Berg <johannes@sipsolutions.net>
Acked-by: Oleg Nesterov <oleg@tv-sign.ru>
Acked-by: Ingo Molnar <mingo@elte.hu>
Acked-by: Peter Zijlstra <a.p.zijlstra@chello.nl>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>
diff --git a/include/linux/workqueue.h b/include/linux/workqueue.h
index ce6badc..7daafdc 100644
--- a/include/linux/workqueue.h
+++ b/include/linux/workqueue.h
@@ -8,6 +8,7 @@
#include <linux/timer.h>
#include <linux/linkage.h>
#include <linux/bitops.h>
+#include <linux/lockdep.h>
#include <asm/atomic.h>
struct workqueue_struct;
@@ -28,6 +29,9 @@
#define WORK_STRUCT_WQ_DATA_MASK (~WORK_STRUCT_FLAG_MASK)
struct list_head entry;
work_func_t func;
+#ifdef CONFIG_LOCKDEP
+ struct lockdep_map lockdep_map;
+#endif
};
#define WORK_DATA_INIT() ATOMIC_LONG_INIT(0)
@@ -41,10 +45,23 @@
struct work_struct work;
};
+#ifdef CONFIG_LOCKDEP
+/*
+ * NB: because we have to copy the lockdep_map, setting _key
+ * here is required, otherwise it could get initialised to the
+ * copy of the lockdep_map!
+ */
+#define __WORK_INIT_LOCKDEP_MAP(n, k) \
+ .lockdep_map = STATIC_LOCKDEP_MAP_INIT(n, k),
+#else
+#define __WORK_INIT_LOCKDEP_MAP(n, k)
+#endif
+
#define __WORK_INITIALIZER(n, f) { \
.data = WORK_DATA_INIT(), \
.entry = { &(n).entry, &(n).entry }, \
.func = (f), \
+ __WORK_INIT_LOCKDEP_MAP(#n, &(n)) \
}
#define __DELAYED_WORK_INITIALIZER(n, f) { \
@@ -76,12 +93,24 @@
* assignment of the work data initializer allows the compiler
* to generate better code.
*/
+#ifdef CONFIG_LOCKDEP
+#define INIT_WORK(_work, _func) \
+ do { \
+ static struct lock_class_key __key; \
+ \
+ (_work)->data = (atomic_long_t) WORK_DATA_INIT(); \
+ lockdep_init_map(&(_work)->lockdep_map, #_work, &__key, 0);\
+ INIT_LIST_HEAD(&(_work)->entry); \
+ PREPARE_WORK((_work), (_func)); \
+ } while (0)
+#else
#define INIT_WORK(_work, _func) \
do { \
(_work)->data = (atomic_long_t) WORK_DATA_INIT(); \
INIT_LIST_HEAD(&(_work)->entry); \
PREPARE_WORK((_work), (_func)); \
} while (0)
+#endif
#define INIT_DELAYED_WORK(_work, _func) \
do { \
@@ -118,9 +147,23 @@
clear_bit(WORK_STRUCT_PENDING, work_data_bits(work))
-extern struct workqueue_struct *__create_workqueue(const char *name,
- int singlethread,
- int freezeable);
+extern struct workqueue_struct *
+__create_workqueue_key(const char *name, int singlethread,
+ int freezeable, struct lock_class_key *key);
+
+#ifdef CONFIG_LOCKDEP
+#define __create_workqueue(name, singlethread, freezeable) \
+({ \
+ static struct lock_class_key __key; \
+ \
+ __create_workqueue_key((name), (singlethread), \
+ (freezeable), &__key); \
+})
+#else
+#define __create_workqueue(name, singlethread, freezeable) \
+ __create_workqueue_key((name), (singlethread), (freezeable), NULL)
+#endif
+
#define create_workqueue(name) __create_workqueue((name), 0, 0)
#define create_freezeable_workqueue(name) __create_workqueue((name), 1, 1)
#define create_singlethread_workqueue(name) __create_workqueue((name), 1, 0)