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/lockdep.h b/include/linux/lockdep.h
index f6279f6..4c4d236 100644
--- a/include/linux/lockdep.h
+++ b/include/linux/lockdep.h
@@ -276,6 +276,14 @@
(lock)->dep_map.key, sub)
/*
+ * To initialize a lockdep_map statically use this macro.
+ * Note that _name must not be NULL.
+ */
+#define STATIC_LOCKDEP_MAP_INIT(_name, _key) \
+ { .name = (_name), .key = (void *)(_key), }
+
+
+/*
* Acquire a lock.
*
* Values for "read":
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)
diff --git a/kernel/lockdep.c b/kernel/lockdep.c
index a6f1ee9..b5392ff 100644
--- a/kernel/lockdep.c
+++ b/kernel/lockdep.c
@@ -1521,7 +1521,7 @@
}
static int validate_chain(struct task_struct *curr, struct lockdep_map *lock,
- struct held_lock *hlock, int chain_head, u64 chain_key)
+ struct held_lock *hlock, int chain_head, u64 chain_key)
{
/*
* Trylock needs to maintain the stack of held locks, but it
diff --git a/kernel/workqueue.c b/kernel/workqueue.c
index e080d1d..d1916fe 100644
--- a/kernel/workqueue.c
+++ b/kernel/workqueue.c
@@ -32,6 +32,7 @@
#include <linux/freezer.h>
#include <linux/kallsyms.h>
#include <linux/debug_locks.h>
+#include <linux/lockdep.h>
/*
* The per-CPU workqueue (if single thread, we always use the first
@@ -61,6 +62,9 @@
const char *name;
int singlethread;
int freezeable; /* Freeze threads during suspend */
+#ifdef CONFIG_LOCKDEP
+ struct lockdep_map lockdep_map;
+#endif
};
/* All the per-cpu workqueues on the system, for hotplug cpu to add/remove
@@ -250,6 +254,17 @@
struct work_struct *work = list_entry(cwq->worklist.next,
struct work_struct, entry);
work_func_t f = work->func;
+#ifdef CONFIG_LOCKDEP
+ /*
+ * It is permissible to free the struct work_struct
+ * from inside the function that is called from it,
+ * this we need to take into account for lockdep too.
+ * To avoid bogus "held lock freed" warnings as well
+ * as problems when looking into work->lockdep_map,
+ * make a copy and use that here.
+ */
+ struct lockdep_map lockdep_map = work->lockdep_map;
+#endif
cwq->current_work = work;
list_del_init(cwq->worklist.next);
@@ -257,7 +272,11 @@
BUG_ON(get_wq_data(work) != cwq);
work_clear_pending(work);
+ lock_acquire(&cwq->wq->lockdep_map, 0, 0, 0, 2, _THIS_IP_);
+ lock_acquire(&lockdep_map, 0, 0, 0, 2, _THIS_IP_);
f(work);
+ lock_release(&lockdep_map, 1, _THIS_IP_);
+ lock_release(&cwq->wq->lockdep_map, 1, _THIS_IP_);
if (unlikely(in_atomic() || lockdep_depth(current) > 0)) {
printk(KERN_ERR "BUG: workqueue leaked lock or atomic: "
@@ -376,6 +395,8 @@
int cpu;
might_sleep();
+ lock_acquire(&wq->lockdep_map, 0, 0, 0, 2, _THIS_IP_);
+ lock_release(&wq->lockdep_map, 1, _THIS_IP_);
for_each_cpu_mask(cpu, *cpu_map)
flush_cpu_workqueue(per_cpu_ptr(wq->cpu_wq, cpu));
}
@@ -446,6 +467,9 @@
might_sleep();
+ lock_acquire(&work->lockdep_map, 0, 0, 0, 2, _THIS_IP_);
+ lock_release(&work->lockdep_map, 1, _THIS_IP_);
+
cwq = get_wq_data(work);
if (!cwq)
return;
@@ -695,8 +719,10 @@
}
}
-struct workqueue_struct *__create_workqueue(const char *name,
- int singlethread, int freezeable)
+struct workqueue_struct *__create_workqueue_key(const char *name,
+ int singlethread,
+ int freezeable,
+ struct lock_class_key *key)
{
struct workqueue_struct *wq;
struct cpu_workqueue_struct *cwq;
@@ -713,6 +739,7 @@
}
wq->name = name;
+ lockdep_init_map(&wq->lockdep_map, name, key, 0);
wq->singlethread = singlethread;
wq->freezeable = freezeable;
INIT_LIST_HEAD(&wq->list);
@@ -741,7 +768,7 @@
}
return wq;
}
-EXPORT_SYMBOL_GPL(__create_workqueue);
+EXPORT_SYMBOL_GPL(__create_workqueue_key);
static void cleanup_workqueue_thread(struct cpu_workqueue_struct *cwq, int cpu)
{
@@ -752,6 +779,9 @@
if (cwq->thread == NULL)
return;
+ lock_acquire(&cwq->wq->lockdep_map, 0, 0, 0, 2, _THIS_IP_);
+ lock_release(&cwq->wq->lockdep_map, 1, _THIS_IP_);
+
flush_cpu_workqueue(cwq);
/*
* If the caller is CPU_DEAD and cwq->worklist was not empty,