From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: Date: Tue, 5 Feb 2019 12:00:42 +0300 From: Vladimir Davydov Subject: Re: [tarantool-patches] Re: [PATCH] Fix fiber_join() hang in case fiber_cancel() was called Message-ID: <20190205090042.vjtymjg7vp52aaki@esperanza> References: <20190204135138.51960-1-sergepetrenko@tarantool.org> <20190204174404.qyalziyrhz6use5g@esperanza> <08B70EC3-6EA3-405B-964F-7C10B5BA62F3@tarantool.org> MIME-Version: 1.0 Content-Type: text/plain; charset="utf-8" Content-Disposition: inline Content-Transfer-Encoding: 8bit In-Reply-To: <08B70EC3-6EA3-405B-964F-7C10B5BA62F3@tarantool.org> To: Serge Petrenko Cc: Georgy Kirichenko , tarantool-patches@freelists.org List-ID: On Tue, Feb 05, 2019 at 09:28:01AM +0300, Serge Petrenko wrote: > > > > 4 февр. 2019 г., в 20:44, Vladimir Davydov 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?