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Fri, 15 Oct 2021 08:27:17 +0000 (UTC) Received: from dovecot-director2.suse.de ([192.168.254.65]) by imap2.suse-dmz.suse.de with ESMTPSA id DTlAH2U7aWHKCQAAMHmgww (envelope-from ); Fri, 15 Oct 2021 08:27:17 +0000 Message-ID: <137e4211-266f-bdb3-6830-e101c27c3be4@suse.cz> Date: Fri, 15 Oct 2021 10:27:17 +0200 MIME-Version: 1.0 User-Agent: Mozilla/5.0 (X11; Linux x86_64; rv:91.0) Gecko/20100101 Thunderbird/91.2.0 Subject: Re: [lib/stackdepot] 1cd8ce52c5: BUG:unable_to_handle_page_fault_for_address Content-Language: en-US To: Mike Rapoport Cc: kernel test robot , 0day robot , Dmitry Vyukov , Marco Elver , Vijayanand Jitta , Maarten Lankhorst , Maxime Ripard , Thomas Zimmermann , David Airlie , Daniel Vetter , Andrey Ryabinin , Alexander Potapenko , Andrey Konovalov , Geert Uytterhoeven , Oliver Glitta , Imran Khan , LKML , lkp@lists.01.org, Andrew Morton , linux-mm@kvack.org, dri-devel@lists.freedesktop.org, intel-gfx@lists.freedesktop.org, kasan-dev@googlegroups.com References: <20211014085450.GC18719@xsang-OptiPlex-9020> <4d99add1-5cf7-c608-a131-18959b85e5dc@suse.cz> From: Vlastimil Babka In-Reply-To: Content-Type: text/plain; charset=UTF-8 Content-Transfer-Encoding: 7bit X-Rspamd-Server: rspam06 X-Rspamd-Queue-Id: 8D79E30000AB X-Stat-Signature: ciq59bmp15mc4cmi7jfshzaqjfypznqg Authentication-Results: imf03.hostedemail.com; dkim=pass header.d=suse.cz header.s=susede2_rsa header.b=jTXff+NM; dkim=pass header.d=suse.cz header.s=susede2_ed25519 header.b=uGC9lMi8; dmarc=none; spf=pass (imf03.hostedemail.com: domain of vbabka@suse.cz designates 195.135.220.28 as permitted sender) smtp.mailfrom=vbabka@suse.cz X-HE-Tag: 1634286438-878840 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 10/14/21 12:16, Mike Rapoport wrote: > On Thu, Oct 14, 2021 at 11:33:03AM +0200, Vlastimil Babka wrote: >> On 10/14/21 10:54, kernel test robot wrote: >> >> In my local testing of the patch, when stackdepot was initialized through >> page owner init, it was using kvmalloc() so slab_is_available() was true. >> Looks like the exact order of slab vs page_owner alloc is non-deterministic, >> could be arch-dependent or just random ordering of init calls. A wrong order >> will exploit the apparent fact that slab_is_available() is not a good >> indicator of using memblock vs page allocator, and we would need a better one. >> Thoughts? > > The order of slab vs page_owner is deterministic, but it is different for > FLATMEM and SPARSEMEM. And page_ext_init_flatmem_late() that initializes > page_ext for FLATMEM is called exactly between buddy and slab setup: Oh, so it was due to FLATMEM, thanks for figuring that out! > static void __init mm_init(void) > { > ... > > mem_init(); > mem_init_print_info(); > /* page_owner must be initialized after buddy is ready */ > page_ext_init_flatmem_late(); > kmem_cache_init(); > > ... > } > > I've stared for a while at page_ext init and it seems that the > page_ext_init_flatmem_late() can be simply dropped because there is anyway > a call to invoke_init_callbacks() in page_ext_init() that is called much > later in the boot process. Yeah, but page_ext_init() only does something for SPARSEMEM, and is empty on FLATMEM. Otherwise it would be duplicating all the work. So I'll just move page_ext_init_flatmem_late() below kmem_cache_init() in mm_init(). Thanks again!