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SubjectRe: [PATCH v2] locking/ww_mutex: Initialize waiter.ww_ctx properly
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@roeck-us.net>
> Suggested-by: Peter Zijlstra <peterz@infradead.org>
> Signed-off-by: Sebastian Andrzej Siewior <bigeasy@linutronix.de>

Tested-by: Guenter Roeck <linux@roeck-us.net>

> ---
> 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
>

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