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[71.184.117.43]) by smtp.gmail.com with ESMTPSA id e19sm1892659qtc.75.2019.12.19.05.16.59 (version=TLS1_3 cipher=TLS_AES_128_GCM_SHA256 bits=128/128); Thu, 19 Dec 2019 05:17:00 -0800 (PST) Content-Type: text/plain; charset=us-ascii Content-Transfer-Encoding: quoted-printable From: Qian Cai Mime-Version: 1.0 (1.0) Subject: Re: [PATCH] mm, debug_pagealloc: don't rely on static keys too early Date: Thu, 19 Dec 2019 08:16:59 -0500 Message-Id: <83B24C03-1484-4DD6-9B42-029FF1B27287@lca.pw> References: <20191219130612.23171-1-vbabka@suse.cz> Cc: Andrew Morton , linux-mm@kvack.org, linux-kernel@vger.kernel.org, stable@vger.kernel.org, Joonsoo Kim , "Kirill A. Shutemov" , Michal Hocko , Matthew Wilcox , Mel Gorman , Peter Zijlstra , Borislav Petkov In-Reply-To: <20191219130612.23171-1-vbabka@suse.cz> To: Vlastimil Babka X-Mailer: iPhone Mail (17C54) X-Bogosity: Ham, tests=bogofilter, spamicity=0.000000, version=1.2.4 Sender: owner-linux-mm@kvack.org Precedence: bulk X-Loop: owner-majordomo@kvack.org List-ID: > On Dec 19, 2019, at 8:06 AM, Vlastimil Babka wrote: >=20 > Commit 96a2b03f281d ("mm, debug_pagelloc: use static keys to enable debugg= ing") > has introduced a static key to reduce overhead when debug_pagealloc is com= piled > in but not enabled. It relied on the assumption that jump_label_init() is > called before parse_early_param() as in start_kernel(), so when the > "debug_pagealloc=3Don" option is parsed, it is safe to enable the static k= ey. >=20 > However, it turns out multiple architectures call parse_early_param() earl= ier > from their setup_arch(). x86 also calls jump_label_init() even earlier, so= no > issue was found while testing the commit, but same is not true for e.g. pp= c64 > and s390 where the kernel would not boot with debug_pagealloc=3Don as foun= d by > our QA. This was daily tested on linux-next here for those arches and never saw an i= ssue. Are you able to reproduce it on mainline or linux-next?=