From mboxrd@z Thu Jan 1 00:00:00 1970 Received: from smtp.kernel.org (aws-us-west-2-korg-mail-1.web.codeaurora.org [10.30.226.201]) (using TLSv1.2 with cipher ECDHE-RSA-AES256-GCM-SHA384 (256/256 bits)) (No client certificate requested) by smtp.subspace.kernel.org (Postfix) with ESMTPS id 6095730F938 for ; Fri, 2 Jan 2026 12:22:47 +0000 (UTC) Authentication-Results: smtp.subspace.kernel.org; arc=none smtp.client-ip=10.30.226.201 ARC-Seal:i=1; a=rsa-sha256; d=subspace.kernel.org; s=arc-20240116; t=1767356569; cv=none; b=jIZcACqK6nduCOlcm1jfDuxyz4M3xK5yt7rvsdkvghLIs/u06fJq0oc7nhI30/0uppncpZBz7zhpkZd48YO2fw5VzhPQjCV0eW2c35JYZewiWJLdHzjFY7y903d2GIDWurE10vGjF38RW/Z/Rr+Md2WkFSQcbyi1B/U+m90zbkY= ARC-Message-Signature:i=1; a=rsa-sha256; d=subspace.kernel.org; s=arc-20240116; t=1767356569; c=relaxed/simple; bh=/y5qJ7sooAfhInidOteSGTuhmPZd8DQCWImJwaX+P2M=; h=Date:From:To:Cc:Subject:Message-ID:References:MIME-Version: Content-Type:Content-Disposition:In-Reply-To; b=AcuxB8aFrb8D4fqvgdLFHKmjiFTI3T0OsXwVFitgZDG0iXuOf/SnKw82qIpRarzA2m7Oj0ulpVu8rOLhnp4/4YCs6iqyLy0k2lnL3L4y9VpyS1lpqc2lbytbVSyGIxXrFayHtF/wmeaL52Hi8H/1huAdE9KjeGwEqVnhWmAsx3A= ARC-Authentication-Results:i=1; smtp.subspace.kernel.org; dkim=pass (1024-bit key) header.d=linuxfoundation.org header.i=@linuxfoundation.org header.b=2btFMDoM; arc=none smtp.client-ip=10.30.226.201 Authentication-Results: smtp.subspace.kernel.org; dkim=pass (1024-bit key) header.d=linuxfoundation.org header.i=@linuxfoundation.org header.b="2btFMDoM" Received: by smtp.kernel.org (Postfix) with ESMTPSA id 8809CC116B1; Fri, 2 Jan 2026 12:22:46 +0000 (UTC) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/simple; d=linuxfoundation.org; s=korg; t=1767356567; bh=/y5qJ7sooAfhInidOteSGTuhmPZd8DQCWImJwaX+P2M=; h=Date:From:To:Cc:Subject:References:In-Reply-To:From; b=2btFMDoMXbSB9075BJeGsrivmHUOm7YYWBj+2fmM/OaVNpoqzg/HZnL7fCPsYNco/ sdFDhFET0ncfFpDy0DECaDjtg3w0Di+9+Ct/UNnG3v7Smam6UFj0RnlaID7wv7zi82 Uw+1QD76OudRkzcdq9tnijIo57wSUvZ5dQMrTmx4= Date: Fri, 2 Jan 2026 13:22:44 +0100 From: Greg KH To: Holger =?iso-8859-1?Q?Hoffst=E4tte?= Cc: "stable@vger.kernel.org" , Sasha Levin , Fernand Sieber Subject: Re: Please add 127b90315ca0 ("sched/proxy: Yield the donor task") to 6.12.y / 6.18.y Message-ID: <2026010235-contort-catwalk-835b@gregkh> References: <04b82346-c38a-08e2-49d5-d64981eb7dae@applied-asynchrony.com> Precedence: bulk X-Mailing-List: stable@vger.kernel.org List-Id: List-Subscribe: List-Unsubscribe: MIME-Version: 1.0 Content-Type: text/plain; charset=iso-8859-1 Content-Disposition: inline Content-Transfer-Encoding: 8bit In-Reply-To: <04b82346-c38a-08e2-49d5-d64981eb7dae@applied-asynchrony.com> On Tue, Dec 30, 2025 at 03:38:34PM +0100, Holger Hoffstätte wrote: > Hi - > > a Gentoo user recently found that 6.18.2 started to reproducuibly > crash when building their go toolchain [1]. > > Apparently the addition of "sched/fair: Forfeit vruntime on yield" > (mainline 79104becf42b) can result in the infamous NULL returned from > pick_eevdf(), which is not supposed to happen. > > It turned out that the mentioned commit triggered a bug related > to the recently added proxy execution feature, which was already > fixed in mainline by "sched/proxy: Yield the donor task" > (127b90315ca0), though not marked for stable. > > Applying this to 6.18.2/.3-rc1 (and probably 6.12 as well) > has reproducibly fixed the problem. A possible reason the crash > was triggered by the Go runtime could be its specific use of yield(), > though that's just speculation on my part. > > So please add 127b90315ca0 ("sched/proxy: Yield the donor task") > to 6.18.y/6.12.y. I know we're already in 6.18.3-rc1, but the > crasher seems reproducible. Now queued up to 6.18.y, thanks. greg k-h