From patchwork Wed Mar 13 19:28:10 2024 Content-Type: text/plain; charset="utf-8" MIME-Version: 1.0 Content-Transfer-Encoding: 7bit X-Patchwork-Submitter: Florian Weimer X-Patchwork-Id: 87153 Return-Path: X-Original-To: patchwork@sourceware.org Delivered-To: patchwork@sourceware.org Received: from server2.sourceware.org (localhost [IPv6:::1]) by sourceware.org (Postfix) with ESMTP id 85DBD385780D for ; Wed, 13 Mar 2024 19:28:40 +0000 (GMT) X-Original-To: libc-alpha@sourceware.org Delivered-To: libc-alpha@sourceware.org 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 2CCCC385780D for ; Wed, 13 Mar 2024 19:28:14 +0000 (GMT) DMARC-Filter: OpenDMARC Filter v1.4.2 sourceware.org 2CCCC385780D Authentication-Results: sourceware.org; dmarc=pass (p=none dis=none) header.from=redhat.com Authentication-Results: sourceware.org; spf=pass smtp.mailfrom=redhat.com ARC-Filter: OpenARC Filter v1.0.0 sourceware.org 2CCCC385780D Authentication-Results: server2.sourceware.org; arc=none smtp.remote-ip=170.10.129.124 ARC-Seal: i=1; a=rsa-sha256; d=sourceware.org; s=key; t=1710358096; cv=none; b=bIpCMt+LlWSLpbyClTFEEKIo8rtuUfmGY4T7o0evZYZiwFEGXZ/IJpObGOGawmyB2e0drlV5ti42sAlAb6zbALEmdZfn7Fu5L7yLjMrJh7U2ywX8YYjUyXbbAb1AtlLHCAcy3+ggLDLbGysSlVK7dXCVsCXUh3qs6zDi9XtN8vQ= ARC-Message-Signature: i=1; a=rsa-sha256; d=sourceware.org; s=key; t=1710358096; c=relaxed/simple; bh=elSppHFEoCEY5x5iOag+bh0ogq1CTNu5wmWxEEHlU8I=; h=DKIM-Signature:From:To:Subject:Date:Message-ID:MIME-Version; b=wb2M0GzkcMVE1JNixqm7rc0dXu6FZUq2BAkrnSgLqTdmKBldTx2aOu9HYvpOehVlR/evwFc5I3a4XBXtIkINcQ6eFPDA66Rj9fmc7DPrLd9ZzG+zd000e9mIBaw6jsFb0HMl04QrN0UtMXAqLGiGyBrbyflQquCyKVjkJrMNMJQ= ARC-Authentication-Results: i=1; server2.sourceware.org DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=redhat.com; s=mimecast20190719; t=1710358093; h=from:from:reply-to:subject:subject:date:date:message-id:message-id: to:to:cc:mime-version:mime-version:content-type:content-type; bh=Emoezyk6k+ibMk6t2M0v0L8y42gcfuNY7cmImv/LZ6k=; b=NwJ//n9dwHoRi/fiv26Te5jMvMkNbua2Sd76S/XNpGfpbvIPwqgPdNfH76za5q7BMaYhvV M465T0eJKFEDAuJYo+LnI6/mcAxBrWtIuiGIizuEudy2XdMlBWSLggCIaFEmTGuvhXmlPZ S/rCDpHsELNeBaGMwHOpIKNPIMFOV+Y= Received: from mimecast-mx02.redhat.com (mimecast-mx02.redhat.com [66.187.233.88]) by relay.mimecast.com with ESMTP with STARTTLS (version=TLSv1.3, cipher=TLS_AES_256_GCM_SHA384) id us-mta-145-B3u16llONcy6A4mbOOXVRA-1; Wed, 13 Mar 2024 15:28:12 -0400 X-MC-Unique: B3u16llONcy6A4mbOOXVRA-1 Received: from smtp.corp.redhat.com (int-mx09.intmail.prod.int.rdu2.redhat.com [10.11.54.9]) (using TLSv1.3 with cipher TLS_AES_256_GCM_SHA384 (256/256 bits) key-exchange X25519 server-signature RSA-PSS (2048 bits) server-digest SHA256) (No client certificate requested) by mimecast-mx02.redhat.com (Postfix) with ESMTPS id 3F856185A783 for ; Wed, 13 Mar 2024 19:28:12 +0000 (UTC) Received: from oldenburg.str.redhat.com (unknown [10.39.192.73]) by smtp.corp.redhat.com (Postfix) with ESMTPS id BDFB7492BC6 for ; Wed, 13 Mar 2024 19:28:11 +0000 (UTC) From: Florian Weimer To: libc-alpha@sourceware.org Subject: [PATCH v3] linux: Use rseq area unconditionally in sched_getcpu (bug 31479) Date: Wed, 13 Mar 2024 20:28:10 +0100 Message-ID: <87y1amnd85.fsf@oldenburg.str.redhat.com> User-Agent: Gnus/5.13 (Gnus v5.13) Emacs/28.3 (gnu/linux) MIME-Version: 1.0 X-Scanned-By: MIMEDefang 3.4.1 on 10.11.54.9 X-Mimecast-Spam-Score: 0 X-Mimecast-Originator: redhat.com X-Spam-Status: No, score=-11.1 required=5.0 tests=BAYES_00, DKIMWL_WL_HIGH, DKIM_SIGNED, DKIM_VALID, DKIM_VALID_AU, DKIM_VALID_EF, GIT_PATCH_0, RCVD_IN_DNSWL_NONE, SPF_HELO_NONE, SPF_NONE, TXREP, T_SCC_BODY_TEXT_LINE autolearn=ham autolearn_force=no version=3.4.6 X-Spam-Checker-Version: SpamAssassin 3.4.6 (2021-04-09) on server2.sourceware.org X-BeenThere: libc-alpha@sourceware.org X-Mailman-Version: 2.1.30 Precedence: list List-Id: Libc-alpha mailing list List-Unsubscribe: , List-Archive: List-Post: List-Help: List-Subscribe: , Errors-To: libc-alpha-bounces+patchwork=sourceware.org@sourceware.org Originally, nptl/descr.h included , but we removed that in commit 2c6b4b272e6b4d07303af25709051c3e96288f2d ("nptl: Unconditionally use a 32-byte rseq area"). After that, it was not ensured that the RSEQ_SIG macro was defined during sched_getcpu.c compilation that provided a definition. This commit always checks the rseq area for CPU number information before using the other approaches. This adds an unnecessary (but well-predictable) branch on architectures which do not define RSEQ_SIG, but its cost is small compared to the system call. Most architectures that have vDSO acceleration for getcpu also have rseq support. Fixes: 2c6b4b272e6b4d07303af25709051c3e96288f2d Fixes: 1d350aa06091211863e41169729cee1bca39f72f Reviewed-by: Arjun Shankar --- v3: Remove #ifdef RSEQ_SIG instead of making it defined. sysdeps/unix/sysv/linux/sched_getcpu.c | 8 -------- 1 file changed, 8 deletions(-) base-commit: 2173173d57971d042c0ad4b281431ae127e9b5b8 diff --git a/sysdeps/unix/sysv/linux/sched_getcpu.c b/sysdeps/unix/sysv/linux/sched_getcpu.c index dfb884568d..72a3360550 100644 --- a/sysdeps/unix/sysv/linux/sched_getcpu.c +++ b/sysdeps/unix/sysv/linux/sched_getcpu.c @@ -33,17 +33,9 @@ vsyscall_sched_getcpu (void) return r == -1 ? r : cpu; } -#ifdef RSEQ_SIG int sched_getcpu (void) { int cpu_id = THREAD_GETMEM_VOLATILE (THREAD_SELF, rseq_area.cpu_id); return __glibc_likely (cpu_id >= 0) ? cpu_id : vsyscall_sched_getcpu (); } -#else /* RSEQ_SIG */ -int -sched_getcpu (void) -{ - return vsyscall_sched_getcpu (); -} -#endif /* RSEQ_SIG */