From mboxrd@z Thu Jan 1 00:00:00 1970 Received: from mail-24420.protonmail.ch (mail-24420.protonmail.ch [109.224.244.20]) (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 123D94F55C7; Mon, 7 Sep 2026 15:44:01 +0000 (UTC) Authentication-Results: smtp.subspace.kernel.org; arc=none smtp.client-ip=109.224.244.20 ARC-Seal:i=1; a=rsa-sha256; d=subspace.kernel.org; s=arc-20240116; t=1788795846; cv=none; b=GCm64SIN8MDvAzC1iAi85wK6WoxokpSu4yBPTS1b3BvvZLkij2nohyQr0Mb96f74duJmLfnOzlXJB/pZU31ncaUXaOZXSPqHD6KZY+MRlDYXSmAXaVU5NHGjnyLsMNCEOnydYxWQJilzZcXCcZC1wxBAcS+rPKfgcphdxwePt38= ARC-Message-Signature:i=1; a=rsa-sha256; d=subspace.kernel.org; s=arc-20240116; t=1788795846; c=relaxed/simple; bh=/FZgfDnGoX+ire10E4Wl1AsaNQpBCMc+mcsKWPqtva8=; h=Date:To:From:Cc:Subject:Message-ID:MIME-Version:Content-Type; b=AFCrMnB8dMbK9FTF6AyHUCqgW/MOZBefHVqeDalxfmG0iHcSDhB0ZRQmnWyfc1cmDrFPwniD7SKmUo8LBHXKXZ8t6quNNsokvZQ08fDeVyghXRY2AhlpFSCSyxzoKO3Fr646Xof39DWlZDqEyRsaCyNrOt4xc9e9BMILElqH92M= ARC-Authentication-Results:i=1; smtp.subspace.kernel.org; dmarc=pass (p=quarantine dis=none) header.from=feldt.systems; spf=pass smtp.mailfrom=feldt.systems; dkim=pass (2048-bit key) header.d=feldt.systems header.i=@feldt.systems header.b=eHm0Yb2t; arc=none smtp.client-ip=109.224.244.20 Authentication-Results: smtp.subspace.kernel.org; dmarc=pass (p=quarantine dis=none) header.from=feldt.systems Authentication-Results: smtp.subspace.kernel.org; spf=pass smtp.mailfrom=feldt.systems Authentication-Results: smtp.subspace.kernel.org; dkim=pass (2048-bit key) header.d=feldt.systems header.i=@feldt.systems header.b="eHm0Yb2t" DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=feldt.systems; s=protonmail2; t=1788795832; x=1789055032; bh=pkR0D31rVu/YiZFmAIFnyb6QlSompEq74ZW7OV+Buog=; h=Date:To:From:Cc:Subject:Message-ID:Feedback-ID:From:To:Cc:Date: Subject:Reply-To:Feedback-ID:Message-ID:BIMI-Selector; b=eHm0Yb2tXkhaq1Hi6N88Jp0UhGxnSj2elmLEjvoPvAnllGYcDqH2TUJx36X34mlwy iFotdLlZ2U9BkDs8kckgvcZaAvhBZeMC55BwCy9wwK2bZvKZbY2pJILN4XO2ikGcJ7 /qME0UbcGiz93AJov3MaTBaMHxLxPDKdpQu/5pgxzk/04VllByj0t4c02Wz+5XDkfD QxC47pNUvUZgPvrOiHCzoftEKdZ6Q8hfbrRCA0bMOtDMdx3w+F5cnU3ryc1/8C6QDr A/p1WF1pd/BxE/Ilht/o9CBUDJqp+ZcFf1lhnW3lpRCuVkS1W0hmkMW+SL02mrF2Iy Z/B5URMOuVxaw== Date: Mon, 07 Sep 2026 15:43:45 +0000 To: tj@kernel.org From: Noah Feldt Cc: carnil@debian.org, cgroups@vger.kernel.org, dschatzberg@meta.com, hannes@cmpxchg.org, linux-kernel@vger.kernel.org, mkoutny@suse.com, peterz@infradead.org, stable@vger.kernel.org, Noah Feldt Subject: Re: [PATCH] cgroup: Avoid iteration of dying tasks with zero refcount Message-ID: <20260907154324.91918-1-noah@feldt.systems> Feedback-ID: 113045274:user:proton X-Pm-Message-ID: ba06ed4c0107d1cb5ab091803c083e11ed334b3d Precedence: bulk X-Mailing-List: cgroups@vger.kernel.org List-Id: List-Subscribe: List-Unsubscribe: MIME-Version: 1.0 Content-Type: multipart/signed; protocol="application/pgp-signature"; micalg=pgp-sha256; boundary="------dbd54100772eff0bbd62aef01cb43fd7b87c958a643f8695175bb7b3b4cd37cc"; charset=utf-8 This is an OpenPGP/MIME signed message (RFC 4880 and 3156) --------dbd54100772eff0bbd62aef01cb43fd7b87c958a643f8695175bb7b3b4cd37cc Content-Type: multipart/mixed; boundary=dc970138a169a5fda25c477f7c7829e7fcd8bc377702300cb4a26856e571 From: Noah Feldt To: tj@kernel.org Cc: carnil@debian.org, cgroups@vger.kernel.org, dschatzberg@meta.com, hannes@cmpxchg.org, linux-kernel@vger.kernel.org, mkoutny@suse.com, peterz@infradead.org, stable@vger.kernel.org, Noah Feldt Subject: Re: [PATCH] cgroup: Avoid iteration of dying tasks with zero refcount Date: Mon, 7 Sep 2026 17:43:24 +0200 Message-ID: <20260907154324.91918-1-noah@feldt.systems> X-Mailer: git-send-email 2.50.1 In-Reply-To: References: <20260902161653.1051794-1-mkoutny@suse.com> MIME-Version: 1.0 --dc970138a169a5fda25c477f7c7829e7fcd8bc377702300cb4a26856e571 Content-Type: text/plain; charset=UTF-8 Content-Transfer-Encoding: 8bit Content-Disposition: inline On Wed, Sep 02, 2026 at 08:59:39AM -1000, Tejun Heo wrote: > How about something like the following? It's more in line with other skips > and the resulting behavior should remain the same as before: > > --- a/kernel/cgroup/cgroup.c > +++ b/kernel/cgroup/cgroup.c > @@ -5228,6 +5229,21 @@ > + if (it->task_pos && it->cur_tasks_head == &it->cur_cset->dying_tasks) { > + task = list_entry(it->task_pos, struct task_struct, cg_list); > + if (!atomic_read(&task->signal->live)) > + css_task_iter_advance(it); > + } I tested this change and the crash did not happen anymore with the second PoC I sent. 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