In the following scenario: code path 1: my_function() -> lock(L1); ...; cancel_work_sync(my_work) [or cancel_rearming_delayed_work(my_work)] code path 2: run_workqueue() -> my_work.f() -> ...; lock(L1); ... you can get a deadlock if my_work.f() is running but my_function() has acquired L1 already. This patch adds a pseudo-lock to each struct work_struct to make lockdep warn about this scenario. Signed-off-by: Johannes Berg Cc: Oleg Nesterov Acked-by: Ingo Molnar Acked-by: Peter Zijlstra --- include/linux/lockdep.h | 8 ++++++++ include/linux/workqueue.h | 29 +++++++++++++++++++++++++++++ kernel/workqueue.c | 16 ++++++++++++++++ 3 files changed, 53 insertions(+) --- linux-2.6-git.orig/include/linux/workqueue.h 2007-07-05 13:01:33.978155045 +0200 +++ linux-2.6-git/include/linux/workqueue.h 2007-07-05 13:07:40.969155045 +0200 @@ -8,6 +8,7 @@ #include #include #include +#include #include struct workqueue_struct; @@ -28,6 +29,9 @@ struct work_struct { #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 execute_work { 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 @@ struct execute_work { * 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 { \ --- linux-2.6-git.orig/kernel/workqueue.c 2007-07-05 13:01:55.728155045 +0200 +++ linux-2.6-git/kernel/workqueue.c 2007-07-05 13:03:40.882155045 +0200 @@ -254,6 +254,17 @@ static void run_workqueue(struct cpu_wor 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); @@ -262,7 +273,9 @@ static void run_workqueue(struct cpu_wor 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)) { @@ -454,6 +467,9 @@ static void wait_on_work(struct work_str 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; --- linux-2.6-git.orig/include/linux/lockdep.h 2007-07-05 13:01:34.043155045 +0200 +++ linux-2.6-git/include/linux/lockdep.h 2007-07-05 13:03:40.901155045 +0200 @@ -223,6 +223,14 @@ extern void lockdep_init_map(struct lock (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": -- - To unsubscribe from this list: send the line "unsubscribe linux-kernel" in the body of a message to majordomo@vger.kernel.org More majordomo info at http://vger.kernel.org/majordomo-info.html Please read the FAQ at http://www.tux.org/lkml/