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authorJohannes Berg <johannes@sipsolutions.net>2007-10-19 02:39:55 -0400
committerLinus Torvalds <torvalds@woody.linux-foundation.org>2007-10-19 14:53:38 -0400
commit4e6045f134784f4b158b3c0f7a282b04bd816887 (patch)
tree3304628f666c8524accd10f40da48cfba8b08608 /kernel
parentcf7b708c8d1d7a27736771bcf4c457b332b0f818 (diff)
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>
Diffstat (limited to 'kernel')
-rw-r--r--kernel/lockdep.c2
-rw-r--r--kernel/workqueue.c36
2 files changed, 34 insertions, 4 deletions
diff --git a/kernel/lockdep.c b/kernel/lockdep.c
index a6f1ee9c92d9..b5392ff7e6a6 100644
--- a/kernel/lockdep.c
+++ b/kernel/lockdep.c
@@ -1521,7 +1521,7 @@ cache_hit:
1521} 1521}
1522 1522
1523static int validate_chain(struct task_struct *curr, struct lockdep_map *lock, 1523static int validate_chain(struct task_struct *curr, struct lockdep_map *lock,
1524 struct held_lock *hlock, int chain_head, u64 chain_key) 1524 struct held_lock *hlock, int chain_head, u64 chain_key)
1525{ 1525{
1526 /* 1526 /*
1527 * Trylock needs to maintain the stack of held locks, but it 1527 * Trylock needs to maintain the stack of held locks, but it
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 @@
32#include <linux/freezer.h> 32#include <linux/freezer.h>
33#include <linux/kallsyms.h> 33#include <linux/kallsyms.h>
34#include <linux/debug_locks.h> 34#include <linux/debug_locks.h>
35#include <linux/lockdep.h>
35 36
36/* 37/*
37 * The per-CPU workqueue (if single thread, we always use the first 38 * The per-CPU workqueue (if single thread, we always use the first
@@ -61,6 +62,9 @@ struct workqueue_struct {
61 const char *name; 62 const char *name;
62 int singlethread; 63 int singlethread;
63 int freezeable; /* Freeze threads during suspend */ 64 int freezeable; /* Freeze threads during suspend */
65#ifdef CONFIG_LOCKDEP
66 struct lockdep_map lockdep_map;
67#endif
64}; 68};
65 69
66/* All the per-cpu workqueues on the system, for hotplug cpu to add/remove 70/* 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)
250 struct work_struct *work = list_entry(cwq->worklist.next, 254 struct work_struct *work = list_entry(cwq->worklist.next,
251 struct work_struct, entry); 255 struct work_struct, entry);
252 work_func_t f = work->func; 256 work_func_t f = work->func;
257#ifdef CONFIG_LOCKDEP
258 /*
259 * It is permissible to free the struct work_struct
260 * from inside the function that is called from it,
261 * this we need to take into account for lockdep too.
262 * To avoid bogus "held lock freed" warnings as well
263 * as problems when looking into work->lockdep_map,
264 * make a copy and use that here.
265 */
266 struct lockdep_map lockdep_map = work->lockdep_map;
267#endif
253 268
254 cwq->current_work = work; 269 cwq->current_work = work;
255 list_del_init(cwq->worklist.next); 270 list_del_init(cwq->worklist.next);
@@ -257,7 +272,11 @@ static void run_workqueue(struct cpu_workqueue_struct *cwq)
257 272
258 BUG_ON(get_wq_data(work) != cwq); 273 BUG_ON(get_wq_data(work) != cwq);
259 work_clear_pending(work); 274 work_clear_pending(work);
275 lock_acquire(&cwq->wq->lockdep_map, 0, 0, 0, 2, _THIS_IP_);
276 lock_acquire(&lockdep_map, 0, 0, 0, 2, _THIS_IP_);
260 f(work); 277 f(work);
278 lock_release(&lockdep_map, 1, _THIS_IP_);
279 lock_release(&cwq->wq->lockdep_map, 1, _THIS_IP_);
261 280
262 if (unlikely(in_atomic() || lockdep_depth(current) > 0)) { 281 if (unlikely(in_atomic() || lockdep_depth(current) > 0)) {
263 printk(KERN_ERR "BUG: workqueue leaked lock or atomic: " 282 printk(KERN_ERR "BUG: workqueue leaked lock or atomic: "
@@ -376,6 +395,8 @@ void fastcall flush_workqueue(struct workqueue_struct *wq)
376 int cpu; 395 int cpu;
377 396
378 might_sleep(); 397 might_sleep();
398 lock_acquire(&wq->lockdep_map, 0, 0, 0, 2, _THIS_IP_);
399 lock_release(&wq->lockdep_map, 1, _THIS_IP_);
379 for_each_cpu_mask(cpu, *cpu_map) 400 for_each_cpu_mask(cpu, *cpu_map)
380 flush_cpu_workqueue(per_cpu_ptr(wq->cpu_wq, cpu)); 401 flush_cpu_workqueue(per_cpu_ptr(wq->cpu_wq, cpu));
381} 402}
@@ -446,6 +467,9 @@ static void wait_on_work(struct work_struct *work)
446 467
447 might_sleep(); 468 might_sleep();
448 469
470 lock_acquire(&work->lockdep_map, 0, 0, 0, 2, _THIS_IP_);
471 lock_release(&work->lockdep_map, 1, _THIS_IP_);
472
449 cwq = get_wq_data(work); 473 cwq = get_wq_data(work);
450 if (!cwq) 474 if (!cwq)
451 return; 475 return;
@@ -695,8 +719,10 @@ static void start_workqueue_thread(struct cpu_workqueue_struct *cwq, int cpu)
695 } 719 }
696} 720}
697 721
698struct workqueue_struct *__create_workqueue(const char *name, 722struct workqueue_struct *__create_workqueue_key(const char *name,
699 int singlethread, int freezeable) 723 int singlethread,
724 int freezeable,
725 struct lock_class_key *key)
700{ 726{
701 struct workqueue_struct *wq; 727 struct workqueue_struct *wq;
702 struct cpu_workqueue_struct *cwq; 728 struct cpu_workqueue_struct *cwq;
@@ -713,6 +739,7 @@ struct workqueue_struct *__create_workqueue(const char *name,
713 } 739 }
714 740
715 wq->name = name; 741 wq->name = name;
742 lockdep_init_map(&wq->lockdep_map, name, key, 0);
716 wq->singlethread = singlethread; 743 wq->singlethread = singlethread;
717 wq->freezeable = freezeable; 744 wq->freezeable = freezeable;
718 INIT_LIST_HEAD(&wq->list); 745 INIT_LIST_HEAD(&wq->list);
@@ -741,7 +768,7 @@ struct workqueue_struct *__create_workqueue(const char *name,
741 } 768 }
742 return wq; 769 return wq;
743} 770}
744EXPORT_SYMBOL_GPL(__create_workqueue); 771EXPORT_SYMBOL_GPL(__create_workqueue_key);
745 772
746static void cleanup_workqueue_thread(struct cpu_workqueue_struct *cwq, int cpu) 773static void cleanup_workqueue_thread(struct cpu_workqueue_struct *cwq, int cpu)
747{ 774{
@@ -752,6 +779,9 @@ static void cleanup_workqueue_thread(struct cpu_workqueue_struct *cwq, int cpu)
752 if (cwq->thread == NULL) 779 if (cwq->thread == NULL)
753 return; 780 return;
754 781
782 lock_acquire(&cwq->wq->lockdep_map, 0, 0, 0, 2, _THIS_IP_);
783 lock_release(&cwq->wq->lockdep_map, 1, _THIS_IP_);
784
755 flush_cpu_workqueue(cwq); 785 flush_cpu_workqueue(cwq);
756 /* 786 /*
757 * If the caller is CPU_DEAD and cwq->worklist was not empty, 787 * If the caller is CPU_DEAD and cwq->worklist was not empty,