Re: [PATCH v2] locking/ww_mutex: Initialize waiter.ww_ctx properly

[Guenter Roeck]

On Thu, Aug 19, 2021 at 09:30:30PM +0200, Sebastian Andrzej Siewior wrote:
> The gathering of the debug code for the ww-mutex initialized moved the
> POISON initialiation into one spot and only set waiter.ww_ctx if the
> ww_ctx was non-NULL thus keeping the POISON value in ww-mutex case.
> 
> For ww-mutex without a context it is expected to set the context to
> NULL, the poison value was intended only for the regular mutex.
> 
> Always initialized waiter.ww_ctx to ww_ctx in the ww-mutex case.
> 
> Fixes: c0afb0ffc06e6 ("locking/ww_mutex: Gather mutex_waiter initialization")
> Reported-by: Guenter Roeck <linux@xxxxxxxxxxxx>
> Suggested-by: Peter Zijlstra <peterz@xxxxxxxxxxxxx>
> Signed-off-by: Sebastian Andrzej Siewior <bigeasy@xxxxxxxxxxxxx>

Tested-by: Guenter Roeck <linux@xxxxxxxxxxxx>

> ---
> v1…v2: Use PeterZ' approach.
> 
>  kernel/locking/mutex.c | 2 +-
>  1 file changed, 1 insertion(+), 1 deletion(-)
> 
> diff --git a/kernel/locking/mutex.c b/kernel/locking/mutex.c
> index 05b68931622d1..2c70213934cd4 100644
> --- a/kernel/locking/mutex.c
> +++ b/kernel/locking/mutex.c
> @@ -614,7 +614,7 @@ __mutex_lock_common(struct mutex *lock, unsigned int state, unsigned int subclas
>  
>  	debug_mutex_lock_common(lock, &waiter);
>  	waiter.task = current;
> -	if (ww_ctx)
> +	if (use_ww_ctx)
>  		waiter.ww_ctx = ww_ctx;
>  
>  	lock_contended(&lock->dep_map, ip);
> -- 
> 2.33.0
>