Re: [PATCH] mutex: fix deadlock injection

[Alex Deucher]

On Tue, Jul 30, 2013 at 4:13 AM, Maarten Lankhorst
<maarten.lankhorst@xxxxxxxxxxxxx> wrote:
> The check needs to be for > 1, because ctx->acquired is already incremented.
> This will prevent ww_mutex_lock_slow from returning -EDEADLK and not locking
> the mutex. It caused a lot of false gpu lockups on radeon with
> CONFIG_DEBUG_WW_MUTEX_SLOWPATH=y because a function that shouldn't be able
> to return -EDEADLK did.
>

I haven't followed the new reservation stuff too closely, but seems plausible.

Acked-by: Alex Deucher <alexander.deucher@xxxxxxx>

> Cc: Alex Deucher <alexander.deucher@xxxxxxx>
> Signed-off-by: Maarten Lankhorst <maarten.lankhorst@xxxxxxxxxxxxx>
> ---
> diff --git a/kernel/mutex.c b/kernel/mutex.c
> index ff05f4b..a52ee7bb 100644
> --- a/kernel/mutex.c
> +++ b/kernel/mutex.c
> @@ -686,7 +686,7 @@ __ww_mutex_lock(struct ww_mutex *lock, struct ww_acquire_ctx *ctx)
>         might_sleep();
>         ret =  __mutex_lock_common(&lock->base, TASK_UNINTERRUPTIBLE,
>                                    0, &ctx->dep_map, _RET_IP_, ctx);
> -       if (!ret && ctx->acquired > 0)
> +       if (!ret && ctx->acquired > 1)
>                 return ww_mutex_deadlock_injection(lock, ctx);
>
>         return ret;
> @@ -702,7 +702,7 @@ __ww_mutex_lock_interruptible(struct ww_mutex *lock, struct ww_acquire_ctx *ctx)
>         ret = __mutex_lock_common(&lock->base, TASK_INTERRUPTIBLE,
>                                   0, &ctx->dep_map, _RET_IP_, ctx);
>
> -       if (!ret && ctx->acquired > 0)
> +       if (!ret && ctx->acquired > 1)
>                 return ww_mutex_deadlock_injection(lock, ctx);
>
>         return ret;
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