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Fri, 24 Apr 2026 01:57:14 -0700 (PDT) X-Received: by 2002:a05:6000:2505:b0:43d:1598:2d6e with SMTP id ffacd0b85a97d-43fe407c3camr47587561f8f.20.1777021033516; Fri, 24 Apr 2026 01:57:13 -0700 (PDT) Received: from redhat.com ([2a02:8012:f011:0:f1ce:ac56:d2cd:7c2e]) by smtp.gmail.com with ESMTPSA id ffacd0b85a97d-43fe4cb1176sm60118353f8f.3.2026.04.24.01.57.12 (version=TLS1_3 cipher=TLS_AES_256_GCM_SHA384 bits=256/256); Fri, 24 Apr 2026 01:57:13 -0700 (PDT) Date: Fri, 24 Apr 2026 09:57:11 +0100 From: Daniel =?utf-8?B?UC4gQmVycmFuZ8Op?= To: Elisey Konstantinov Cc: qemu-devel@nongnu.org, pbonzini@redhat.com, marcandre.lureau@redhat.com, philmd@linaro.org Subject: Re: [PATCH] build: prefer sigaltstack over ucontext on Linux Message-ID: References: <616E96C0-F0A5-4A9E-A63B-3BC1B5F18094@gmail.com> MIME-Version: 1.0 Content-Type: text/plain; charset=utf-8 Content-Disposition: inline In-Reply-To: <616E96C0-F0A5-4A9E-A63B-3BC1B5F18094@gmail.com> User-Agent: Mutt/2.3.1 (2026-03-20) 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: -20 X-Spam_score: -2.1 X-Spam_bar: -- X-Spam_report: (-2.1 / 5.0 requ) BAYES_00=-1.9, DKIMWL_WL_HIGH=-0.001, 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_MSPIKE_H4=0.001, RCVD_IN_MSPIKE_WL=0.001, SPF_HELO_PASS=-0.001, SPF_PASS=-0.001 autolearn=ham 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: , Reply-To: Daniel =?utf-8?B?UC4gQmVycmFuZ8Op?= Errors-To: qemu-devel-bounces+qemu-devel=archiver.kernel.org@nongnu.org Sender: qemu-devel-bounces+qemu-devel=archiver.kernel.org@nongnu.org On Fri, Apr 24, 2026 at 11:19:39AM +0300, Elisey Konstantinov wrote: > From 517099e65de1e2ad3d0f33d3c4a7a71f8728279c Mon Sep 17 00:00:00 2001 > From: Elisey > Date: Mon, 23 Mar 2026 16:02:45 +0100 > Subject: [PATCH] build: prefer sigaltstack over ucontext on Linux > > sigaltstack coroutine backend is more stable on some Linux > configurations, while ucontext causes boot failures for certain > PPC Mac OS X guests (issue #3276). > Select sigaltstack first when available, keeping ucontext as fallback > until the underlying issue is resolved. IMHO there needs to be a greater investigation in to why ucontext would be demonstrating the failure. ucontext has been the default on Linux for QEMU for decades without significant issues, so my concern is that switching to sigaltstack is not fixing the root cause of the bug you see, just masking it by luck. The choice of coroutine backend can also be performance sensitive and so changing it is something that would need to also bring along performance benchmark data to illustrate the likely impact of the change. > > Signed-off-by: Elisey Konstantinov > --- > meson.build | 4 +++- > 1 file changed, 3 insertions(+), 1 deletion(-) > > diff --git a/meson.build b/meson.build > index ab3e97eb9f..742655e007 100644 > --- a/meson.build > +++ b/meson.build > @@ -505,10 +505,12 @@ if host_os == 'windows' > elif host_os == 'emscripten' > supported_backends += ['wasm'] > else > + # FIXME: This is a temporary workaround! > + # SigAltStack is in higher priority to fix #3276 > + supported_backends += ['sigaltstack'] > if host_os != 'darwin' and cc.links(ucontext_probe) > supported_backends += ['ucontext'] > endif > - supported_backends += ['sigaltstack'] > endif > > if coroutine_backend == 'auto' > -- > 2.50.1 (Apple Git-155) >