From mboxrd@z Thu Jan 1 00:00:00 1970 X-Spam-Checker-Version: SpamAssassin 3.4.4 (2020-01-24) on polar.synack.me X-Spam-Level: X-Spam-Status: No, score=-1.9 required=5.0 tests=BAYES_00 autolearn=unavailable autolearn_force=no version=3.4.4 Path: eternal-september.org!reader01.eternal-september.org!reader02.eternal-september.org!feeder.eternal-september.org!aioe.org!.POSTED!not-for-mail From: "Dmitry A. Kazakov" Newsgroups: comp.lang.ada Subject: Re: Reference counter in smart pointers are not updated properly when used by multiple tasks Date: Thu, 1 Feb 2018 11:57:48 +0100 Organization: Aioe.org NNTP Server Message-ID: References: <634ea4dc-af9e-46d2-815b-af5a3aa2f6cd@googlegroups.com> NNTP-Posting-Host: MyFhHs417jM9AgzRpXn7yg.user.gioia.aioe.org Mime-Version: 1.0 Content-Type: text/plain; charset=utf-8; format=flowed Content-Transfer-Encoding: 7bit X-Complaints-To: abuse@aioe.org User-Agent: Mozilla/5.0 (Windows NT 6.1; WOW64; rv:52.0) Gecko/20100101 Thunderbird/52.5.2 Content-Language: en-US X-Notice: Filtered by postfilter v. 0.8.2 Xref: reader02.eternal-september.org comp.lang.ada:50248 Date: 2018-02-01T11:57:48+01:00 List-Id: On 01/02/2018 11:01, onox wrote: > On Thursday, February 1, 2018 at 9:39:24 AM UTC+1, Dmitry A. Kazakov wrote: >> On 01/02/2018 06:52, onox wrote: >> >>> So the smart pointers are not working properly when there are jobs (paired with the same >>> smart pointer) being executed by multiple workers. >> >> Depends on the implementation. Surely handling reference counts must be >> done in a task-safe manner, e.g. through a protected action. Pragma >> Atomic is no help here. > > You're right Dimitry, using a protected object instead fixes the > problem. But I do not understand why __sync_sub_and_fetch_4 is not > sufficient. Subtract-and-fetch should work, if present and returns the resulted value, pragma Atomic should not. It is kind of difficult to use GCC built-ins. -- Regards, Dmitry A. Kazakov http://www.dmitry-kazakov.de