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 lists.ozlabs.org (lists.ozlabs.org [112.213.38.117]) (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 521F0C761A6 for ; Tue, 28 Mar 2023 11:33:32 +0000 (UTC) Received: from boromir.ozlabs.org (localhost [IPv6:::1]) by lists.ozlabs.org (Postfix) with ESMTP id 4Pm6y26lktz3f3n for ; Tue, 28 Mar 2023 22:33:30 +1100 (AEDT) Authentication-Results: lists.ozlabs.org; dkim=pass (2048-bit key; unprotected) header.d=ellerman.id.au header.i=@ellerman.id.au header.a=rsa-sha256 header.s=201909 header.b=AMpWTwQ2; dkim-atps=neutral Received: from gandalf.ozlabs.org (gandalf.ozlabs.org [150.107.74.76]) (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 lists.ozlabs.org (Postfix) with ESMTPS id 4Pm6x263rHz2yNy for ; Tue, 28 Mar 2023 22:32:38 +1100 (AEDT) Authentication-Results: lists.ozlabs.org; dkim=pass (2048-bit key; unprotected) header.d=ellerman.id.au header.i=@ellerman.id.au header.a=rsa-sha256 header.s=201909 header.b=AMpWTwQ2; dkim-atps=neutral Received: from authenticated.ozlabs.org (localhost [127.0.0.1]) (using TLSv1.3 with cipher TLS_AES_256_GCM_SHA384 (256/256 bits) key-exchange X25519 server-signature RSA-PSS (4096 bits) server-digest SHA256) (No client certificate requested) by mail.ozlabs.org (Postfix) with ESMTPSA id 4Pm6x1521Lz4xFW; Tue, 28 Mar 2023 22:32:37 +1100 (AEDT) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=ellerman.id.au; s=201909; t=1680003157; bh=g372AUSYfnay8EGETnHTvUJW5p9CXx9A6ULuph62ckc=; h=From:To:Subject:In-Reply-To:References:Date:From; b=AMpWTwQ2QLoAJs9gTwNfc9vqTMryykrPnsJ5Zx+AosUyWmihI8sKIT260sayJHydL npFqwYK82sMcFdaffPRj5CcC80VIiEFudEjBWC/PygAPe9yuyORMbl7Ubz3qR+BodI h4x7VQfROWnrJdwHq3I4FGoWRQKYNe2lPzbDIZTeTF09lHTbO3Ovk0yCSB+i8L//l3 uzK/4/QcxLCFto3CTtpteUsVgC+DMrrYLo8yLh02m9XRXiI04gL0YuABgJYv9auAt9 vLaQvhjIxBhRhuZHjQHU6OM2Ad91qCz8G6nMHrxkfwp3WamJGrsMX/HItAOf+u87rh xK2GfEJi2rXtQ== From: Michael Ellerman To: Jens Axboe , "linuxppc-dev@lists.ozlabs.org" Subject: Re: [PATCH] powerpc: don't try to copy ppc for task with NULL pt_regs In-Reply-To: References: Date: Tue, 28 Mar 2023 22:32:34 +1100 Message-ID: <87lejhcdrh.fsf@mpe.ellerman.id.au> MIME-Version: 1.0 Content-Type: text/plain X-BeenThere: linuxppc-dev@lists.ozlabs.org X-Mailman-Version: 2.1.29 Precedence: list List-Id: Linux on PowerPC Developers Mail List List-Unsubscribe: , List-Archive: List-Post: List-Help: List-Subscribe: , Errors-To: linuxppc-dev-bounces+linuxppc-dev=archiver.kernel.org@lists.ozlabs.org Sender: "Linuxppc-dev" Jens Axboe writes: > Powerpc sets up PF_KTHREAD and PF_IO_WORKER with a NULL pt_regs, which > from my (arguably very short) checking is not commonly done for other > archs. This is fine, except when PF_IO_WORKER's have been created and > the task does something that causes a coredump to be generated. Do kthread's ever core dump? I didn't think they did, but I can't find any logic to prevent it. Maybe it's always been possible but just never happened due to luck. As Nick said we should probably have a non-NULL regs for PF_IO_WORKERS, but I'll still take this as a nice backportable fix for the immediate crash. I tagged it as Fixes: pointing back at the commit that added ppr_get(), even though I don't know for sure the bug was triggerable back then (v4.8). cheers