From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: X-Spam-Checker-Version: SpamAssassin 3.4.0 (2014-02-07) on aws-us-west-2-korg-lkml-1.web.codeaurora.org Received: from lists1p.gnu.org (lists1p.gnu.org [209.51.188.17]) (using TLSv1.2 with cipher ECDHE-RSA-AES256-GCM-SHA384 (256/256 bits)) (No client certificate requested) by smtp.lore.kernel.org (Postfix) with ESMTPS id 59659CC6B34 for ; Thu, 15 Oct 2026 11:21:33 +0000 (UTC) Received: from localhost ([::1] helo=lists1p.gnu.org) by lists1p.gnu.org with esmtp (Exim 4.90_1) (envelope-from ) id 1xHJWR-0002CR-KR; Thu, 15 Oct 2026 07:21:19 -0400 Received: from eggs.gnu.org ([2001:470:142:3::10]) by lists1p.gnu.org with esmtps (TLS1.2:ECDHE_RSA_AES_256_GCM_SHA384:256) (Exim 4.90_1) (envelope-from ) id 1xHJWP-00029G-FA for qemu-devel@nongnu.org; Thu, 15 Oct 2026 07:21:17 -0400 Received: from us-smtp-delivery-124.mimecast.com ([170.10.129.124]) by eggs.gnu.org with esmtps (TLS1.2:ECDHE_RSA_AES_256_GCM_SHA384:256) (Exim 4.90_1) (envelope-from ) id 1xHJWN-00043x-UB for qemu-devel@nongnu.org; Thu, 15 Oct 2026 07:21:17 -0400 DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=redhat.com; s=mimecast20190719; t=1792063275; h=from:from:reply-to:subject:subject:date:date:message-id:message-id: to:to:cc:cc:mime-version:mime-version:content-type:content-type: content-transfer-encoding:content-transfer-encoding: in-reply-to:in-reply-to:references:references; bh=lGCv+AfKMnU61s9G0ocGnKK177Rsaciih/XA+CS5lHg=; b=XChsOuamm44nXm6DHpPe/80ro66+eYIaMWaNWk26uTWGdt5qXr0u21zvNZT1tacdNmIlg1 QQgrIMYr2kETLZIyLPrbhvgADy6KdklFi40PMyV/8fSOBEvlmkuVy1Kskxs0GHGp3wg+dy rxtqw8fyGRZ0da7EF/KSzrAz92bnQfM= Received: from mx-prod-mc-01.mail-002.prod.us-west-2.aws.redhat.com (ec2-54-186-198-63.us-west-2.compute.amazonaws.com [54.186.198.63]) by relay.mimecast.com with ESMTP with STARTTLS (version=TLSv1.3, cipher=TLS_AES_256_GCM_SHA384) id us-mta-141-yUCRfPbLNoK9D_HpSsS9rQ-1; Thu, 15 Oct 2026 11:21:11 +0000 X-MC-Unique: yUCRfPbLNoK9D_HpSsS9rQ-1 X-Mimecast-MFC-AGG-ID: yUCRfPbLNoK9D_HpSsS9rQ_1792063270 Received: from mx-prod-int-08.mail-002.prod.us-west-2.aws.redhat.com (mx-prod-int-08.mail-002.prod.us-west-2.aws.redhat.com [10.30.177.111]) (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 mx-prod-mc-01.mail-002.prod.us-west-2.aws.redhat.com (Postfix) with ESMTPS id 7DDD81955EB9; Thu, 15 Oct 2026 11:21:10 +0000 (UTC) Received: from berrange.csb (headnet04.pony-001.prod.iad2.dc.redhat.com [10.2.32.116]) by mx-prod-int-08.mail-002.prod.us-west-2.aws.redhat.com (Postfix) with ESMTP id 1D9821800257; Thu, 15 Oct 2026 11:21:06 +0000 (UTC) From: =?UTF-8?q?Daniel=20P=2E=20Berrang=C3=A9?= To: qemu-devel@nongnu.org Cc: =?UTF-8?q?Marc-Andr=C3=A9=20Lureau?= , Michael Roth , =?UTF-8?q?Philippe=20Mathieu-Daud=C3=A9?= , Fabiano Rosas , Richard Henderson , "Dr. David Alan Gilbert" , Paolo Bonzini , Markus Armbruster , Pierrick Bouvier , Eric Blake , =?UTF-8?q?Daniel=20P=2E=20Berrang=C3=A9?= , Laurent Vivier Subject: [PATCH 05/21] util: expand alternate signal stack to all threads Date: Thu, 15 Oct 2026 12:20:28 +0100 Message-ID: <20261015112044.1999748-6-berrange@redhat.com> In-Reply-To: <20261015112044.1999748-1-berrange@redhat.com> References: <20261015112044.1999748-1-berrange@redhat.com> MIME-Version: 1.0 Content-Type: text/plain; charset=UTF-8 Content-Transfer-Encoding: 8bit X-Scanned-By: MIMEDefang 3.4.1 on 10.30.177.111 Received-SPF: pass client-ip=170.10.129.124; envelope-from=berrange@redhat.com; helo=us-smtp-delivery-124.mimecast.com X-Spam_score_int: 10 X-Spam_score: 1.0 X-Spam_bar: + X-Spam_report: (1.0 / 5.0 requ) BAYES_00=-1.9, DKIMWL_WL_HIGH=-0.24, DKIM_SIGNED=0.1, DKIM_VALID=-0.1, DKIM_VALID_AU=-0.1, DKIM_VALID_EF=-0.1, RCVD_IN_DNSWL_NONE=-0.0001, RCVD_IN_SBL_CSS=3.335, SPF_HELO_PASS=-0.001, SPF_PASS=-0.001 autolearn=no autolearn_force=no X-Spam_action: no action X-BeenThere: qemu-devel@nongnu.org X-Mailman-Version: 2.1.29 Precedence: list List-Id: qemu development List-Unsubscribe: , List-Archive: List-Post: List-Help: List-Subscribe: , Errors-To: qemu-devel-bounces+qemu-devel=archiver.kernel.org@nongnu.org Sender: qemu-devel-bounces+qemu-devel=archiver.kernel.org@nongnu.org The sigaltstack() function is per thread, so setting SA_ONSTACK has no effect unless all threads have an alternate signal stack registered. This adds overhead of SIGSTKSZ bytes per thread, which is OS-dependent, but on Linux is 8kb. Signed-off-by: Daniel P. Berrangé --- util/qemu-thread-posix.c | 20 ++++++++++++++++++++ 1 file changed, 20 insertions(+) diff --git a/util/qemu-thread-posix.c b/util/qemu-thread-posix.c index 089606c93fb..66858018057 100644 --- a/util/qemu-thread-posix.c +++ b/util/qemu-thread-posix.c @@ -381,12 +381,28 @@ typedef struct { char *name; } QemuThreadArgs; +static void qemu_thread_sigstack_free(void *data) +{ + stack_t sigstack = { + .ss_sp = NULL, + .ss_size = 0, + .ss_flags = SS_DISABLE, + }; + sigaltstack(&sigstack, NULL); + g_free(data); +} + static void *qemu_thread_start(void *args) { QemuThreadArgs *qemu_thread_args = args; void *(*start_routine)(void *) = qemu_thread_args->start_routine; void *arg = qemu_thread_args->arg; void *r; + stack_t sigstack = { + .ss_sp = g_new0(char, SIGSTKSZ), + .ss_size = SIGSTKSZ, + .ss_flags = 0, + }; if (qemu_thread_args->name) { qemu_thread_set_name(qemu_thread_args->name); @@ -395,6 +411,9 @@ static void *qemu_thread_start(void *args) g_free(qemu_thread_args->name); g_free(qemu_thread_args); + sigaltstack(&sigstack, NULL); + pthread_cleanup_push(qemu_thread_sigstack_free, sigstack.ss_sp); + /* * GCC 11 with glibc 2.17 on PowerPC reports * @@ -413,6 +432,7 @@ static void *qemu_thread_start(void *args) pthread_cleanup_push(qemu_thread_atexit_notify, NULL); r = start_routine(arg); pthread_cleanup_pop(1); + pthread_cleanup_pop(1); #pragma GCC diagnostic pop -- 2.56.0