From 4e6045f134784f4b158b3c0f7a282b04bd816887 Mon Sep 17 00:00:00 2001 From: Johannes Berg Date: Thu, 18 Oct 2007 23:39:55 -0700 Subject: 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 Acked-by: Oleg Nesterov Acked-by: Ingo Molnar Acked-by: Peter Zijlstra Signed-off-by: Andrew Morton Signed-off-by: Linus Torvalds --- kernel/workqueue.c | 36 +++++++++++++++++++++++++++++++++--- 1 file changed, 33 insertions(+), 3 deletions(-) (limited to 'kernel/workqueue.c') diff --git a/kernel/workqueue.c b/kernel/workqueue.c index e080d1d744cc..d1916fea7108 100644 --- a/kernel/workqueue.c +++ b/kernel/workqueue.c @@ -32,6 +32,7 @@ #include #include #include +#include /* * The per-CPU workqueue (if single thread, we always use the first @@ -61,6 +62,9 @@ struct workqueue_struct { 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 @@ static void run_workqueue(struct cpu_workqueue_struct *cwq) 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 @@ static void run_workqueue(struct cpu_workqueue_struct *cwq) 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 @@ void fastcall flush_workqueue(struct workqueue_struct *wq) 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 @@ static void wait_on_work(struct work_struct *work) 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 @@ static void start_workqueue_thread(struct cpu_workqueue_struct *cwq, int cpu) } } -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 @@ struct workqueue_struct *__create_workqueue(const char *name, } 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 @@ struct workqueue_struct *__create_workqueue(const char *name, } 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 @@ static void cleanup_workqueue_thread(struct cpu_workqueue_struct *cwq, int cpu) 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, -- cgit v1.2.3