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Thu, 21 Oct 2021 17:51:20 +0000 (UTC) Received: from dovecot-director2.suse.de ([192.168.254.65]) by imap2.suse-dmz.suse.de with ESMTPSA id p9V5GJiocWGLFgAAMHmgww (envelope-from ); Thu, 21 Oct 2021 17:51:20 +0000 Message-ID: <2a692365-cfa1-64f2-34e0-8aa5674dce5e@suse.cz> Date: Thu, 21 Oct 2021 19:51:20 +0200 MIME-Version: 1.0 User-Agent: Mozilla/5.0 (X11; Linux x86_64; rv:91.0) Gecko/20100101 Thunderbird/91.2.0 Content-Language: en-US To: Jani Nikula , Naresh Kamboju , open list , Linux-Next Mailing List , linux-mm , dri-devel@lists.freedesktop.org, Andrew Morton Cc: Marco Elver , Vijayanand Jitta , Maarten Lankhorst , Maxime Ripard , Thomas Zimmermann , David Airlie , Daniel Vetter , Andrey Ryabinin , Alexander Potapenko , Andrey Konovalov , Dmitry Vyukov , Geert Uytterhoeven , Oliver Glitta , Imran Khan , lkft-triage@lists.linaro.org, Stephen Rothwell References: <80ab567d-74f3-e14b-3c30-e64bbd64b354@suse.cz> <87fssuojoc.fsf@intel.com> From: Vlastimil Babka Subject: Re: [next] [dragonboard 410c] Unable to handle kernel paging request at virtual address 00000000007c4240 In-Reply-To: <87fssuojoc.fsf@intel.com> Content-Type: text/plain; charset=UTF-8 Content-Transfer-Encoding: 7bit X-Stat-Signature: wf6gr1x9k8zrir8gtt33edo5e33xnmby X-Rspamd-Server: rspam01 X-Rspamd-Queue-Id: 1629E190F Authentication-Results: imf22.hostedemail.com; dkim=pass header.d=suse.cz header.s=susede2_rsa header.b=PnEvVpjO; dkim=pass header.d=suse.cz header.s=susede2_ed25519 header.b=NmH9BRpd; dmarc=none; spf=pass (imf22.hostedemail.com: domain of vbabka@suse.cz designates 195.135.220.29 as permitted sender) smtp.mailfrom=vbabka@suse.cz X-HE-Tag: 1634838680-943248 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 10/21/21 10:40, Jani Nikula wrote: > On Thu, 21 Oct 2021, Vlastimil Babka wrote: >> This one seems a bit more tricky and I could really use some advice. >> cd06ab2fd48f adds stackdepot usage to drm_modeset_lock which itself has a >> number of different users and requiring those to call stack_depot_init() >> would be likely error prone. Would it be ok to add the call of >> stack_depot_init() (guarded by #ifdef CONFIG_DRM_DEBUG_MODESET_LOCK) to >> drm_modeset_lock_init()? It will do a mutex_lock()/unlock(), and kvmalloc() >> on first call. >> I don't know how much of hotpath this is, but hopefully should be acceptable >> in debug config. Or do you have better suggestion? Thanks. > > I think that should be fine. > > Maybe add __drm_stack_depot_init() in the existing #if > IS_ENABLED(CONFIG_DRM_DEBUG_MODESET_LOCK), similar to the other > __drm_stack_depot_*() functions, with an empty stub for > CONFIG_DRM_DEBUG_MODESET_LOCK=n, and call it unconditionally in > drm_modeset_lock_init(). Good idea. >> Then we have to figure out how to order a fix between DRM and mmotm... > > That is the question! The problem exists only in the merge of the > two. On current DRM side stack_depot_init() exists but it's __init and > does not look safe to call multiple times. And obviously my changes > don't exist at all in mmotm. > > I guess one (admittedly hackish) option is to first add a patch in > drm-next (or drm-misc-next) that makes it safe to call > stack_depot_init() multiple times in non-init context. It would be > dropped in favour of your changes once the trees get merged together. > > Or is there some way for __drm_stack_depot_init() to detect whether it > should call stack_depot_init() or not, i.e. whether your changes are > there or not? Let's try the easiest approach first. AFAIK mmotm series is now split to pre-next and post-next part and moving my patch lib-stackdepot-allow-optional-init-and-stack_table-allocation-by-kvmalloc.patch with the following fixup to the post-next part should solve this. Would that work, Andrew? Thanks. ----8<---- >From 719e91df5571034b62fa992f6738b00f8d29020e Mon Sep 17 00:00:00 2001 From: Vlastimil Babka Date: Thu, 21 Oct 2021 19:43:33 +0200 Subject: [PATCH] lib/stackdepot: allow optional init and stack_table allocation by kvmalloc() - fixup3 Due to cd06ab2fd48f ("drm/locking: add backtrace for locking contended locks without backoff") landing recently to -next adding a new stack depot user in drivers/gpu/drm/drm_modeset_lock.c we need to add an appropriate call to stack_depot_init() there as well. Signed-off-by: Vlastimil Babka --- drivers/gpu/drm/drm_modeset_lock.c | 9 +++++++++ 1 file changed, 9 insertions(+) diff --git a/drivers/gpu/drm/drm_modeset_lock.c b/drivers/gpu/drm/drm_modeset_lock.c index c97323365675..918065982db4 100644 --- a/drivers/gpu/drm/drm_modeset_lock.c +++ b/drivers/gpu/drm/drm_modeset_lock.c @@ -107,6 +107,11 @@ static void __drm_stack_depot_print(depot_stack_handle_t stack_depot) kfree(buf); } + +static void __drm_stack_depot_init(void) +{ + stack_depot_init(); +} #else /* CONFIG_DRM_DEBUG_MODESET_LOCK */ static depot_stack_handle_t __drm_stack_depot_save(void) { @@ -115,6 +120,9 @@ static depot_stack_handle_t __drm_stack_depot_save(void) static void __drm_stack_depot_print(depot_stack_handle_t stack_depot) { } +static void __drm_stack_depot_init(void) +{ +} #endif /* CONFIG_DRM_DEBUG_MODESET_LOCK */ /** @@ -359,6 +367,7 @@ void drm_modeset_lock_init(struct drm_modeset_lock *lock) { ww_mutex_init(&lock->mutex, &crtc_ww_class); INIT_LIST_HEAD(&lock->head); + __drm_stack_depot_init(); } EXPORT_SYMBOL(drm_modeset_lock_init); -- 2.33.0