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From: Vladimir Davydov <vdavydov.dev@gmail.com>
To: Serge Petrenko <sergepetrenko@tarantool.org>
Cc: Georgy Kirichenko <georgy@tarantool.org>,
	tarantool-patches@freelists.org
Subject: Re: [tarantool-patches] Re: [PATCH] Fix fiber_join() hang in case fiber_cancel() was called
Date: Tue, 5 Feb 2019 12:00:42 +0300	[thread overview]
Message-ID: <20190205090042.vjtymjg7vp52aaki@esperanza> (raw)
In-Reply-To: <08B70EC3-6EA3-405B-964F-7C10B5BA62F3@tarantool.org>

On Tue, Feb 05, 2019 at 09:28:01AM +0300, Serge Petrenko wrote:
> 
> 
> > 4 февр. 2019 г., в 20:44, Vladimir Davydov <vdavydov.dev@gmail.com> написал(а):
> > 
> >> 
> >> diff --git a/src/fiber.c b/src/fiber.c
> >> index 6f3d0ab78..4dc6b3c5a 100644
> >> --- a/src/fiber.c
> >> +++ b/src/fiber.c
> >> @@ -392,9 +392,17 @@ fiber_join(struct fiber *fiber)
> >> 	assert(fiber->flags & FIBER_IS_JOINABLE);
> >> 
> >> 	if (! fiber_is_dead(fiber)) {
> >> -		rlist_add_tail_entry(&fiber->wake, fiber(), state);
> >> 
> >> 		do {
> >> +			/*
> >> +			 * In case fiber is cancelled during yield
> >> +			 * it will be removed from wake queue by a
> >> +			 * wakeup following the cancel.
> >> +			 * Having multiple entries for the same fiber
> >> +			 * doesn't hurt, since wakeup is executed only
> >> +			 * once per fiber.
> >> +			 */
> >> +			rlist_add_tail_entry(&fiber->wake, fiber(), state);
> > 
> > I don't quite like the idea that cancelling a fiber that is joining
> > another fiber will have no effect until the other fiber has exited.
> > Can't we break the loop if fiber_is_cancelled()?
> 
> We can do that. But then we have to set FIBER_IS_JOINABLE to false
> for the joined fiber so that it executes fiber_recycle().

Why should we? IMO the user should be free to kill a fiber executing
fiber_join. If that happens, the joinable fiber shouldn't be collected
until another fiber joins it successfully. This would be consistent with
pthread_join behavior.

> Otherwise it will leak.  Is it ok?

  reply	other threads:[~2019-02-05  9:00 UTC|newest]

Thread overview: 5+ messages / expand[flat|nested]  mbox.gz  Atom feed  top
2019-02-04 13:51 Serge Petrenko
2019-02-04 17:44 ` Vladimir Davydov
2019-02-05  6:28   ` [tarantool-patches] " Serge Petrenko
2019-02-05  9:00     ` Vladimir Davydov [this message]
2019-02-05 15:02       ` Serge Petrenko

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