Re: [PATCH] rtmutex: enable deadlock detection in ww_mutex_lock functions

[Paul Gortmaker <paul.gortmaker@windriver.com>]

On Tue, Jan 20, 2015 at 3:02 PM, Gustavo Bittencourt <gbitten@gmail.com> wrote:
> The functions ww_mutex_lock_interruptible and ww_mutex_lock should return -EDEADLK when faced with
> a deadlock. To do so, the paramenter detect_deadlock in rt_mutex_slowlock must be TRUE.
> This patch corrects potential deadlocks when running PREEMPT_RT with nouveau driver.
>
> Kernel version: 3.14.25-rt22

You might want to have a look at this:

http://www.spinics.net/lists/linux-rt-users/msg12259.html

as it also impacts what the deadlock detection flag does.

Paul.
--

>
> Signed-off-by: Gustavo Bittencourt <gbitten@gmail.com>
> ---
>  kernel/locking/rtmutex.c | 4 ++--
>  1 file changed, 2 insertions(+), 2 deletions(-)
>
> diff --git a/kernel/locking/rtmutex.c b/kernel/locking/rtmutex.c
> index 6c40660..3f6ef91 100644
> --- a/kernel/locking/rtmutex.c
> +++ b/kernel/locking/rtmutex.c
> @@ -1965,7 +1965,7 @@ __ww_mutex_lock_interruptible(struct ww_mutex *lock, struct ww_acquire_ctx *ww_c
>         might_sleep();
>
>         mutex_acquire(&lock->base.dep_map, 0, 0, _RET_IP_);
> -       ret = rt_mutex_slowlock(&lock->base.lock, TASK_INTERRUPTIBLE, NULL, 0, ww_ctx);
> +       ret = rt_mutex_slowlock(&lock->base.lock, TASK_INTERRUPTIBLE, NULL, 1, ww_ctx);
>         if (ret)
>                 mutex_release(&lock->base.dep_map, 1, _RET_IP_);
>         else if (!ret && ww_ctx->acquired > 1)
> @@ -1984,7 +1984,7 @@ __ww_mutex_lock(struct ww_mutex *lock, struct ww_acquire_ctx *ww_ctx)
>
>         mutex_acquire_nest(&lock->base.dep_map, 0, 0, &ww_ctx->dep_map,
>                         _RET_IP_);
> -       ret = rt_mutex_slowlock(&lock->base.lock, TASK_UNINTERRUPTIBLE, NULL, 0, ww_ctx);
> +       ret = rt_mutex_slowlock(&lock->base.lock, TASK_UNINTERRUPTIBLE, NULL, 1, ww_ctx);
>         if (ret)
>                 mutex_release(&lock->base.dep_map, 1, _RET_IP_);
>         else if (!ret && ww_ctx->acquired > 1)
> --
> 1.9.1
>
> --
> To unsubscribe from this list: send the line "unsubscribe linux-rt-users" in
> the body of a message to majordomo@vger.kernel.org
> More majordomo info at  http://vger.kernel.org/majordomo-info.html