From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: Received: from us-smtp-delivery-124.mimecast.com (us-smtp-delivery-124.mimecast.com [170.10.129.124]) by sourceware.org (Postfix) with ESMTPS id C464F3856DDE for ; Thu, 14 Apr 2022 15:56:03 +0000 (GMT) DMARC-Filter: OpenDMARC Filter v1.4.1 sourceware.org C464F3856DDE Received: from mimecast-mx02.redhat.com (mimecast-mx02.redhat.com [66.187.233.88]) by relay.mimecast.com with ESMTP with STARTTLS (version=TLSv1.2, cipher=TLS_ECDHE_RSA_WITH_AES_256_GCM_SHA384) id us-mta-633-hyARi0H8PRCxpleOnXXgGQ-1; Thu, 14 Apr 2022 11:55:59 -0400 X-MC-Unique: hyARi0H8PRCxpleOnXXgGQ-1 Received: from smtp.corp.redhat.com (int-mx01.intmail.prod.int.rdu2.redhat.com [10.11.54.1]) (using TLSv1.2 with cipher AECDH-AES256-SHA (256/256 bits)) (No client certificate requested) by mimecast-mx02.redhat.com (Postfix) with ESMTPS id 7DDD41014A62; Thu, 14 Apr 2022 15:55:59 +0000 (UTC) Received: from oldenburg.str.redhat.com (unknown [10.39.193.61]) by smtp.corp.redhat.com (Postfix) with ESMTPS id 992824087D61; Thu, 14 Apr 2022 15:55:58 +0000 (UTC) From: Florian Weimer To: Adhemerval Zanella Cc: libc-alpha@sourceware.org, Aurelien Jarno Subject: Re: [PATCH] nptl: Handle spurious EINTR when thread cancellation is disabled (BZ#29029) References: <20220407132602.1689442-1-adhemerval.zanella@linaro.org> <87y20bk6vo.fsf@oldenburg.str.redhat.com> <44695f1d-0a88-9557-9ffc-673b49b0c3b3@linaro.org> Date: Thu, 14 Apr 2022 17:55:56 +0200 In-Reply-To: <44695f1d-0a88-9557-9ffc-673b49b0c3b3@linaro.org> (Adhemerval Zanella's message of "Thu, 14 Apr 2022 12:49:58 -0300") Message-ID: <87a6cnwtf7.fsf@oldenburg.str.redhat.com> User-Agent: Gnus/5.13 (Gnus v5.13) Emacs/27.2 (gnu/linux) MIME-Version: 1.0 X-Scanned-By: MIMEDefang 2.84 on 10.11.54.1 X-Mimecast-Spam-Score: 0 X-Mimecast-Originator: redhat.com Content-Type: text/plain X-Spam-Status: No, score=-4.8 required=5.0 tests=BAYES_00, DKIMWL_WL_HIGH, DKIM_SIGNED, DKIM_VALID, DKIM_VALID_AU, DKIM_VALID_EF, RCVD_IN_DNSWL_LOW, RCVD_IN_MSPIKE_H4, RCVD_IN_MSPIKE_WL, SPF_HELO_NONE, SPF_NONE, TXREP, T_SCC_BODY_TEXT_LINE autolearn=ham autolearn_force=no version=3.4.4 X-Spam-Checker-Version: SpamAssassin 3.4.4 (2020-01-24) on server2.sourceware.org X-BeenThere: libc-alpha@sourceware.org X-Mailman-Version: 2.1.29 Precedence: list List-Id: Libc-alpha mailing list List-Unsubscribe: , List-Archive: List-Post: List-Help: List-Subscribe: , X-List-Received-Date: Thu, 14 Apr 2022 15:56:05 -0000 * Adhemerval Zanella: > On 11/04/2022 11:54, Florian Weimer wrote: >> * Adhemerval Zanella: >> >>> @@ -56,10 +63,29 @@ __pthread_disable_asynccancel (int oldtype) >>> { >> >>> + /* We cannot return when we are being canceled. Upon return the >>> + thread might be things which would have to be undone. The >>> + following loop should loop until the cancellation signal is >>> + delivered. */ >>> + while (__glibc_unlikely ((newval & (CANCELING_BITMASK | CANCELED_BITMASK)) >>> + == CANCELING_BITMASK)) >>> + { >>> + futex_wait_simple ((unsigned int *) &self->cancelhandling, newval, >>> + FUTEX_PRIVATE); >>> + newval = atomic_load_relaxed (&self->cancelhandling); >>> + } >> >> Is there no FUTEX_WAKE in the patch because futex_wait_simple already >> fails with EINTR once the signal finally arrives? > > My understanding is it tries to handle interrupted syscall with side > effects on thread with async cancellation enabled where pthread_cancel > was issued, but SIGCANCEL has not yet arrived. In this case the > cancellation handler will handle thread cancellation. Ah, right, this must be it. The comment is clear enough, I just had the wrong mental model. > This restores the previous semantic, which I think it not fully correct > (the old BZ#12683). It wasn't fully fixed anyway. Thanks, Florian