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Date: Mon, 20 Dec 2010 17:28:02 +0800 From: Yong Zhang <yong.zhang0@...il.com> To: Andy Walls <awalls@...metrocast.net> Cc: linux-kernel@...r.kernel.org, nicolas.mailhot@...oste.net, Tejun Heo <tj@...nel.org>, Jarod Wilson <jarod@...hat.com>, Ingo Molnar <mingo@...hat.com>, Mauro Carvalho Chehab <mchehab@...hat.com>, Hans Verkuil <hverkuil@...all.nl> Subject: Re: [PATCH] kthread_worker: Initialize dynamically allocated spinlock properly for lockdep On Mon, Dec 20, 2010 at 3:07 PM, Yong Zhang <yong.zhang0@...il.com> wrote: > On Sun, Dec 19, 2010 at 8:49 PM, Andy Walls <awalls@...metrocast.net> wrote: >> init_kthread_worker(), via KTHREAD_WORKER_INIT(), used an >> initializer for static spin_lock objects, SPIN_LOCK_UNLOCKED, on >> a dynamically allocated kthread_worker object's internal spinlock_t. >> This causes lockdep to gripe: >> >> INFO: trying to register non-static key. >> the code is fine but needs lockdep annotation. >> turning off the locking correctness validator. >> >> To keep lockdep happy, use spin_lock_init() for dynamically >> allocated kthread_worker objects' internal spinlock_t. >> >> Reported-by: Nicolas <nicolas.mailhot@...oste.net> >> Signed-off-by: Andy Walls <awalls@...metrocast.net> >> >> Cc: Tejun Heo <tj@...nel.org> >> Cc: Jarod Wilson <jarod@...hat.com> >> Cc: Ingo Molnar <mingo@...hat.com> >> Cc: Mauro Carvalho Chehab <mchehab@...hat.com> >> Cc: Hans Verkuil <hverkuil@...all.nl> >> >> diff --git a/include/linux/kthread.h b/include/linux/kthread.h >> index 685ea65..e65d0b1 100644 >> --- a/include/linux/kthread.h >> +++ b/include/linux/kthread.h >> @@ -83,7 +83,13 @@ struct kthread_work { >> >> static inline void init_kthread_worker(struct kthread_worker *worker) >> { >> - *worker = (struct kthread_worker)KTHREAD_WORKER_INIT(*worker); >> + /* >> + * Lockdep complains if a dynamically allocated worker's spinlock_t >> + * is initialzed using SPIN_LOCK_UNLOCKED. >> + */ >> + spin_lock_init(&worker->lock); > > This will make different kthead_worker->lock initialized with one same > key. You know spin_lock_init() will be like below: > # define raw_spin_lock_init(lock) \ > do { \ > static struct lock_class_key __key; \ > \ > __raw_spin_lock_init((lock), #lock, &__key); \ > } while (0) > > So we should put the real initializer to kernel/kthread.c > and make init_kthread_worker() to be a MACRO. > > BTW, init_kthread_work() should also be changed like above > because member done is a wait_queue_head. untested patch is here. Andy/Nicolas, is it ok for you? --- Subject: [PATCH] kthread_work: Make lockdep happy spinlock in kthread_worker and wait_queue_head in kthread_work both should be lockdep annotated. So change the interface to make it suiltable for CONFIG_LOCKDEP. Signed-off-by: Yong Zhang <yong.zhang0@...il.com> --- I'm not sure if it's possible to define a worker on stack? So I left DEFINE_KTHREAD_WORKER() untouched. include/linux/kthread.h | 37 +++++++++++++++++++++++++++---------- kernel/kthread.c | 9 +++++++++ 2 files changed, 36 insertions(+), 10 deletions(-) diff --git a/include/linux/kthread.h b/include/linux/kthread.h index 685ea65..5d516b3 100644 --- a/include/linux/kthread.h +++ b/include/linux/kthread.h @@ -75,22 +75,39 @@ struct kthread_work { .flushing = ATOMIC_INIT(0), \ } +/* Is it possible to define a worker on stack? */ #define DEFINE_KTHREAD_WORKER(worker) \ struct kthread_worker worker = KTHREAD_WORKER_INIT(worker) #define DEFINE_KTHREAD_WORK(work, fn) \ struct kthread_work work = KTHREAD_WORK_INIT(work, fn) -static inline void init_kthread_worker(struct kthread_worker *worker) -{ - *worker = (struct kthread_worker)KTHREAD_WORKER_INIT(*worker); -} - -static inline void init_kthread_work(struct kthread_work *work, - kthread_work_func_t fn) -{ - *work = (struct kthread_work)KTHREAD_WORK_INIT(*work, fn); -} +#ifdef CONFIG_LOCKDEP +# define KTHREAD_WORK_INIT_ONSTACK(work, fn) \ + ({init_kthread_work((&work), fn); work}) +# define DEFINE_KTHREAD_WORK_ONSTACK(work, fn) \ + struct kthread_work work = KTHREAD_WORK_INIT_ONSTACK(work, fn) +#else +# define DEFINE_KTHREAD_WORK_ONSTACK(work, fn) DEFINE_KTHREAD_WORK(work, fn) +#endif + +extern void __init_kthread_worker(struct kthread_worker *worker, + struct lock_class_key *key); + +#define init_kthread_worker(worker) \ + do { \ + static struct lock_class_key __key; \ + __init_kthread_worker((worker), &__key); \ + } while (0) + +#define init_kthread_work(work, fn) \ + do { \ + memset((work), 0, sizeof(struct kthread_work)); \ + INIT_LIST_HEAD(&(work)->node); \ + (work)->func = (fn); \ + init_waitqueue_head(&(work)->done); \ + (work)->flushing = ATOMIC_INIT(0); \ + } while (0) int kthread_worker_fn(void *worker_ptr); diff --git a/kernel/kthread.c b/kernel/kthread.c index 2dc3786..fae2eff 100644 --- a/kernel/kthread.c +++ b/kernel/kthread.c @@ -265,6 +265,15 @@ int kthreadd(void *unused) return 0; } +void __init_kthread_worker(struct kthread_worker *worker, + struct lock_class_key *key) +{ + spin_lock_init(&worker->lock); + lockdep_set_class(&worker->lock, key); + INIT_LIST_HEAD(&worker->work_list); + worker->task == NULL; +} + /** * kthread_worker_fn - kthread function to process kthread_worker * @worker_ptr: pointer to initialized kthread_worker -- 1.7.0.4 -- Only stand for myself. -- To unsubscribe from this list: send the line "unsubscribe linux-kernel" in the body of a message to majordomo@...r.kernel.org More majordomo info at http://vger.kernel.org/majordomo-info.html Please read the FAQ at http://www.tux.org/lkml/
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