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([2a09:bac6:37a8:ec8::179:1b]) by smtp.gmail.com with ESMTPSA id ffacd0b85a97d-49c5f5972a7sm6417589f8f.21.2026.11.13.10.57.12 (version=TLS1_3 cipher=TLS_AES_256_GCM_SHA384 bits=256/256); Fri, 13 Nov 2026 10:57:13 -0800 (PST) From: Matt Fleming To: Andrew Morton , Marco Elver Cc: Alexander Potapenko , Andrey Konovalov , Dmitry Vyukov , Oscar Salvador , Vlastimil Babka , Caleb Kan , Caleb Kan , linux-mm@kvack.org, linux-kernel@vger.kernel.org, kasan-dev@googlegroups.com, kernel-team@cloudflare.com, Matt Fleming Subject: [PATCH v3 05/10] drm/locking: print deadlock backtraces with stack_depot_snprint() Date: Fri, 13 Nov 2026 18:56:57 +0000 Message-ID: <20261113185702.1332171-6-matt@readmodwrite.com> X-Mailer: git-send-email 2.43.0 In-Reply-To: <20261113185702.1332171-1-matt@readmodwrite.com> References: <20261113185702.1332171-1-matt@readmodwrite.com> X-Archived-By: MIME-Version: 1.0 Content-Transfer-Encoding: 8bit X-Rspamd-Queue-Id: 46A9318000E X-Rspamd-Server: rspam12 X-Stat-Signature: 9dwgasr3ommur97d7dpxqdux5j1xga7r X-Rspam-User: X-Spam-Status: No, score=-16.8 required=3.0 tests=BAYES_00,DKIM_SIGNED, DKIM_VALID,HEADER_FROM_DIFFERENT_DOMAINS,INCLUDES_CR_TRAILER, INCLUDES_PATCH,MAILING_LIST_MULTI,SPF_HELO_PASS,SPF_PASS, USER_AGENT_GIT autolearn=ham autolearn_force=no version=4.0.1 X-HE-Tag: 1794596235-179246 X-HE-Meta: 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 YWEpj0mq 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 Sender: owner-linux-mm@kvack.org Precedence: bulk X-Loop: owner-majordomo@kvack.org List-ID: List-Subscribe: X-Spam-Checker-Version: SpamAssassin 4.0.1 (2024-03-26) on aws-us-west-2-korg-listserv-alma10-1 From: Caleb Kan When a modeset lock acquisition returns -EDEADLK, DRM saves the call chain and prints it if the caller later attempts another lock or drops its locks without first calling drm_modeset_backoff(). This diagnostic currently fetches the saved stack through stack_depot_fetch(). Later patches compress the frames of persistent stack depot records and remove stack_depot_fetch(), which cannot return a pointer to them. Use stack_depot_snprint() to format the stack. Keep the PAGE_SIZE buffer and leave the warning text, existing indentation, and backtrace unchanged. Signed-off-by: Caleb Kan [mfleming: reworded for compressed frames] Signed-off-by: Matt Fleming --- drivers/gpu/drm/drm_modeset_lock.c | 5 +---- 1 file changed, 1 insertion(+), 4 deletions(-) diff --git a/drivers/gpu/drm/drm_modeset_lock.c b/drivers/gpu/drm/drm_modeset_lock.c index e14814c30d8c..f48b02379b71 100644 --- a/drivers/gpu/drm/drm_modeset_lock.c +++ b/drivers/gpu/drm/drm_modeset_lock.c @@ -94,16 +94,13 @@ static noinline depot_stack_handle_t __drm_stack_depot_save(void) static void __drm_stack_depot_print(depot_stack_handle_t stack_depot) { struct drm_printer p = drm_dbg_printer(NULL, DRM_UT_KMS, "drm_modeset_lock"); - unsigned long *entries; - unsigned int nr_entries; char *buf; buf = kmalloc(PAGE_SIZE, GFP_NOWAIT | __GFP_NOWARN); if (!buf) return; - nr_entries = stack_depot_fetch(stack_depot, &entries); - stack_trace_snprint(buf, PAGE_SIZE, entries, nr_entries, 2); + stack_depot_snprint(stack_depot, buf, PAGE_SIZE, 2); drm_printf(&p, "attempting to lock a contended lock without backoff:\n%s", buf); -- 2.43.0