Re: [tarantool-patches] Re: [PATCH] Fix fiber_join() hang in case fiber_cancel() was called

[Serge Petrenko <sergepetrenko@tarantool.org>]

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> 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(). Otherwise it will leak.
Is it ok?

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