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authorJohannes Berg <johannes@sipsolutions.net>2007-10-18 23:39:55 -0700
committerLinus Torvalds <torvalds@woody.linux-foundation.org>2007-10-19 11:53:38 -0700
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 a6f1ee9c92d..b5392ff7e6a 100644
--- a/kernel/lockdep.c
+++ b/kernel/lockdep.c
@@ -1521,7 +1521,7 @@ cache_hit:
}
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 e080d1d744c..d1916fea710 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 @@ 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,