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Date: Thu, 13 Jun 2019 17:27:35 +0300
From: Vladimir Davydov <vdavydov.dev@gmail.com>
Subject: Re: [tarantool-patches] [PATCH v3 10/14] core: latch_unlock_external
 routine
Message-ID: <20190613142735.f4aoatxq7kxnlwps@esperanza>
References: <cover.1560112747.git.georgy@tarantool.org>
 <98f0889a17245be64f1753012419e92c7ceef4e7.1560112747.git.georgy@tarantool.org>
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In-Reply-To: <98f0889a17245be64f1753012419e92c7ceef4e7.1560112747.git.georgy@tarantool.org>
To: Georgy Kirichenko <georgy@tarantool.org>
Cc: tarantool-patches@freelists.org
List-ID: <tarantool-patches.dev.tarantool.org>

On Sun, Jun 09, 2019 at 11:44:39PM +0300, Georgy Kirichenko wrote:
> Allow unlock a latch from a fiber which isn't owner of the latch. This
> is required to process transaction triggers asynchronously.
> 
> Prerequisites: #1254
> ---
>  src/box/alter.cc     |  2 +-
>  src/lib/core/latch.h | 13 +++++++++++--
>  2 files changed, 12 insertions(+), 3 deletions(-)
> 
> diff --git a/src/box/alter.cc b/src/box/alter.cc
> index 671209b51..adf30c9b6 100644
> --- a/src/box/alter.cc
> +++ b/src/box/alter.cc
> @@ -3446,7 +3446,7 @@ unlock_after_dd(struct trigger *trigger, void *event)
>  {
>  	(void) trigger;
>  	(void) event;
> -	latch_unlock(&schema_lock);
> +	latch_unlock_external(&schema_lock);
>  }
>  
>  static void
> diff --git a/src/lib/core/latch.h b/src/lib/core/latch.h
> index 49c59cf63..b27d6dd08 100644
> --- a/src/lib/core/latch.h
> +++ b/src/lib/core/latch.h
> @@ -159,9 +159,8 @@ latch_trylock(struct latch *l)
>   * \copydoc box_latch_unlock
>   */
>  static inline void
> -latch_unlock(struct latch *l)
> +latch_unlock_external(struct latch *l)
>  {
> -	assert(l->owner == fiber());
>  	l->owner = NULL;
>  	if (!rlist_empty(&l->queue)) {
>  		struct fiber *f = rlist_first_entry(&l->queue,
> @@ -176,6 +175,16 @@ latch_unlock(struct latch *l)
>  	}
>  }
>  
> +/**
> + * \copydoc box_latch_unlock
> + */
> +static inline void
> +latch_unlock(struct latch *l)
> +{
> +	assert(l->owner == fiber());
> +	latch_unlock_external(l);
> +}

Again, looks like a temporary hack to me. I would rather not commit it.
The right way would be getting rid of the schema_lock. I know that you
have tried, but failed because of vylog. I'll look what we can do about
it.