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SubjectRe: [RFC PATCH 01/11] locking/ww_mutex: Remove wakeups from under mutex::wait_lock
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On 10/3/22 17:44, Connor O'Brien wrote:
> diff --git a/kernel/locking/ww_mutex.h b/kernel/locking/ww_mutex.h
> index 56f139201f24..dfc174cd96c6 100644
> --- a/kernel/locking/ww_mutex.h
> +++ b/kernel/locking/ww_mutex.h
> @@ -161,6 +161,11 @@ static inline void lockdep_assert_wait_lock_held(struct rt_mutex *lock)
>
> #endif /* WW_RT */
>
> +void ww_ctx_wake(struct ww_acquire_ctx *ww_ctx)
> +{
> + wake_up_q(&ww_ctx->wake_q);
> +}
> +
> /*
> * Wait-Die:
> * The newer transactions are killed when:
> @@ -284,7 +289,7 @@ __ww_mutex_die(struct MUTEX *lock, struct MUTEX_WAITER *waiter,
> #ifndef WW_RT
> debug_mutex_wake_waiter(lock, waiter);
> #endif
> - wake_up_process(waiter->task);
> + wake_q_add(&ww_ctx->wake_q, waiter->task);
> }
>
> return true;
> @@ -331,7 +336,7 @@ static bool __ww_mutex_wound(struct MUTEX *lock,
> * wakeup pending to re-read the wounded state.
> */
> if (owner != current)
> - wake_up_process(owner);
> + wake_q_add(&ww_ctx->wake_q, owner);
>
> return true;
> }
> diff --git a/kernel/sched/core.c b/kernel/sched/core.c
> index ee28253c9ac0..617e737392be 100644
> --- a/kernel/sched/core.c
> +++ b/kernel/sched/core.c
> @@ -1013,6 +1013,13 @@ void wake_up_q(struct wake_q_head *head)
> wake_up_process(task);
> put_task_struct(task);
> }
> + /*
> + * XXX connoro: seems this is needed now that ww_ctx_wake() passes in a
> + * wake_q_head that is embedded in struct ww_acquire_ctx rather than
> + * declared locally.
> + */
> + head->first = node;
> + head->lastp = &head->first;
> }
>

You shouldn't do wake_q_init() here in wake_up_q(). Instead, you should
do it in ww_ctx_wake() right after the wake_up_q() call.

Cheers,
Longman

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