From mboxrd@z Thu Jan 1 00:00:00 1970 Received: from mail-pg1-f169.google.com (mail-pg1-f169.google.com [209.85.215.169]) (using TLSv1.2 with cipher ECDHE-RSA-AES128-GCM-SHA256 (128/128 bits)) (No client certificate requested) by smtp.subspace.kernel.org (Postfix) with ESMTPS id A9C03393DE8 for ; Sat, 23 Aug 2025 07:43:12 +0000 (UTC) Authentication-Results: smtp.subspace.kernel.org; arc=none smtp.client-ip=209.85.215.169 ARC-Seal:i=1; a=rsa-sha256; d=subspace.kernel.org; s=arc-20240116; t=1755934994; cv=none; b=Otc6lsrSp36MNRwrBfGTveKzSpnnFhp8fERJT0ZuRuNNy1MGY0ZJy9Xx3tc9lX4MAXXVvPGgUr/oBcGfL0u3YI3CMoIVMpn9hcngbxhZ8k51FFdSQFoEKN51rLLXizURIeE5fHBl3v4Q0OVa71CI+C5QJSMUpSOaenYE/6Cm54w= ARC-Message-Signature:i=1; a=rsa-sha256; d=subspace.kernel.org; s=arc-20240116; t=1755934994; c=relaxed/simple; bh=6UIZ7ESj9tVzgEhrGqLwMkKj8QEBxY3cjbR4+80KyA8=; h=From:To:Cc:Subject:Date:Message-ID:In-Reply-To:References: MIME-Version; b=pr8GWaUDu1Y+2riNME4gasmmSeYZOD0xuvxCcOcMr7+P5bv80AhtHLhJDXUe1dAU3BF/D8W7Ona0en50ZHI9qZnksvu367qD1vHqkDpMC7w3jgF9ZV+ZPat+mkzdgRH6izwweD5eZDQhIgVsQ3FIylobRJJmD/oBBGVv897DFf8= ARC-Authentication-Results:i=1; smtp.subspace.kernel.org; dmarc=fail (p=none dis=none) header.from=linux.dev; spf=pass smtp.mailfrom=gmail.com; arc=none smtp.client-ip=209.85.215.169 Authentication-Results: smtp.subspace.kernel.org; dmarc=fail (p=none dis=none) header.from=linux.dev Authentication-Results: smtp.subspace.kernel.org; spf=pass smtp.mailfrom=gmail.com Received: by mail-pg1-f169.google.com with SMTP id 41be03b00d2f7-b482fd89b0eso2077885a12.2 for ; Sat, 23 Aug 2025 00:43:12 -0700 (PDT) X-Google-DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=1e100.net; s=20230601; t=1755934992; x=1756539792; h=content-transfer-encoding:mime-version:references:in-reply-to :message-id:date:subject:cc:to:from:x-gm-message-state:from:to:cc :subject:date:message-id:reply-to; bh=qZPX8X0B5I+s5hVLSY+6qsXOHCGUOeVZARWEgGlLC+I=; b=G7CFbxpI9dJOvArfc80BB/pOwNcKTUgbnYcSYWTtiDB6PhrVjQui7KvT4VFxE+7r9N iFqS0jIc1Q/FbKEg/wt0R7HAU5HUbmQtCrZKDsEJvDlJV463sylH8WglC+71R3XDPQ7E sWGn6lpoFNmS3pIRbxB2RlBlr/nYFbsi7XwBwoidesuCu8/bNXpYgHdlRXxTuDd5H0Fm lt0LrSCoN2hv+mgg97n3r6iqY3kUEqPIdTW3Vxi2fRjfHzp6ya+fgrTWydt9ZMQqhgQx GolOCRk7PwcjjqJJTHW5g0jqdj1LjMClF/wVvpF+0Py/L3evNJ0Q3uXVPg0akx2vuL4B 1oXg== X-Forwarded-Encrypted: i=1; AJvYcCXW2+bAG0QaYSyCTghvl1viYaJ2O8BD00RJV88384vyNgCiowZBuxWkklEpAAb054KGGBPnqwh75sJ0@lists.linux-m68k.org X-Gm-Message-State: AOJu0YxQSx5FNoAqEcVckfIJPE8bQYUJUx7HxPuuHeVNg3yXh3xtge0r ZGTFCy/CYKyrfaCZtain+P+NDL0VmazH60Yvrs0GQezUpAj76uGO+eg6 X-Gm-Gg: ASbGnctsCEKaGzywKPv/pXTGm7HMWJ/vvdvldl2XF/2Doni1KellgDxEqPgJ/ZxW0KP Y9ywFNnrprYLI9ii9JBigTzR1IBq5IVMCtimroWxIOMdxna6C7QXgDVAlcRZL5gi2ys//kDrUBU yI6jlz79mHGM25fRmH3hX0su50B3cAI2pwtkHFhdNqAhrmR2ETndJ3x9Qpisgp/qwWrE/JJlVQm shRDlnCpeBUchRDa0rAZFQXWqjmquNUQIiDw7XkGx1V6JWS4bG4QTRqxAIrlaKXdTg/NWpd0MXw 7fNBc95koMDZ/G82tOISPvaMA5P7OZXmoU63JrvrFA7aQlwlAhJJGNPbivVYQwARwWaqfdwBtGS IMZzHToESDvtdZcLwJA== X-Google-Smtp-Source: AGHT+IF0f2BQBSqWg3im1sdbkd//7GHSpBtH/wvKmeKJ5tjPncO4wHGFIpJvnnP3TVkq8/iiJDhfaA== X-Received: by 2002:a17:903:32c4:b0:246:5a41:e6ee with SMTP id d9443c01a7336-2465a41e7fbmr42588545ad.15.1755934991900; Sat, 23 Aug 2025 00:43:11 -0700 (PDT) Received: from localhost.localdomain ([2403:2c80:17::10:4030]) by smtp.gmail.com with ESMTPSA id d9443c01a7336-246687af234sm15592435ad.48.2025.08.23.00.43.01 (version=TLS1_3 cipher=TLS_CHACHA20_POLY1305_SHA256 bits=256/256); Sat, 23 Aug 2025 00:43:11 -0700 (PDT) From: Lance Yang To: akpm@linux-foundation.org, fthain@linux-m68k.org, geert@linux-m68k.org, mhiramat@kernel.org, senozhatsky@chromium.org Cc: lance.yang@linux.dev, amaindex@outlook.com, anna.schumaker@oracle.com, boqun.feng@gmail.com, ioworker0@gmail.com, joel.granados@kernel.org, jstultz@google.com, kent.overstreet@linux.dev, leonylgao@tencent.com, linux-kernel@vger.kernel.org, linux-m68k@lists.linux-m68k.org, longman@redhat.com, mingo@redhat.com, mingzhe.yang@ly.com, oak@helsinkinet.fi, peterz@infradead.org, rostedt@goodmis.org, tfiga@chromium.org, will@kernel.org, stable@vger.kernel.org Subject: [PATCH 1/1] hung_task: fix warnings by enforcing alignment on lock structures Date: Sat, 23 Aug 2025 15:40:48 +0800 Message-ID: <20250823074048.92498-1-lance.yang@linux.dev> X-Mailer: git-send-email 2.49.0 In-Reply-To: References: Precedence: bulk X-Mailing-List: linux-m68k@vger.kernel.org List-Id: List-Subscribe: List-Unsubscribe: MIME-Version: 1.0 Content-Transfer-Encoding: 8bit From: Lance Yang The blocker tracking mechanism assumes that lock pointers are at least 4-byte aligned to use their lower bits for type encoding. However, as reported by Geert Uytterhoeven, some architectures like m68k only guarantee 2-byte alignment of 32-bit values. This breaks the assumption and causes two related WARN_ON_ONCE checks to trigger. To fix this, enforce a minimum of 4-byte alignment on the core lock structures supported by the blocker tracking mechanism. This ensures the algorithm's alignment assumption now holds true on all architectures. This patch adds __aligned(4) to the definitions of "struct mutex", "struct semaphore", and "struct rw_semaphore", resolving the warnings. Thanks to Geert for bisecting! Reported-by: Geert Uytterhoeven Closes: https://lore.kernel.org/lkml/CAMuHMdW7Ab13DdGs2acMQcix5ObJK0O2dG_Fxzr8_g58Rc1_0g@mail.gmail.com Fixes: e711faaafbe5 ("hung_task: replace blocker_mutex with encoded blocker") Cc: Signed-off-by: Lance Yang --- include/linux/mutex_types.h | 2 +- include/linux/rwsem.h | 2 +- include/linux/semaphore.h | 2 +- 3 files changed, 3 insertions(+), 3 deletions(-) diff --git a/include/linux/mutex_types.h b/include/linux/mutex_types.h index fdf7f515fde8..de798bfbc4c7 100644 --- a/include/linux/mutex_types.h +++ b/include/linux/mutex_types.h @@ -51,7 +51,7 @@ struct mutex { #ifdef CONFIG_DEBUG_LOCK_ALLOC struct lockdep_map dep_map; #endif -}; +} __aligned(4); /* For hung_task blocker tracking, which encodes type in LSBs */ #else /* !CONFIG_PREEMPT_RT */ /* diff --git a/include/linux/rwsem.h b/include/linux/rwsem.h index f1aaf676a874..f6ecf4a4710d 100644 --- a/include/linux/rwsem.h +++ b/include/linux/rwsem.h @@ -64,7 +64,7 @@ struct rw_semaphore { #ifdef CONFIG_DEBUG_LOCK_ALLOC struct lockdep_map dep_map; #endif -}; +} __aligned(4); /* For hung_task blocker tracking, which encodes type in LSBs */ #define RWSEM_UNLOCKED_VALUE 0UL #define RWSEM_WRITER_LOCKED (1UL << 0) diff --git a/include/linux/semaphore.h b/include/linux/semaphore.h index 89706157e622..ac9b9c87bfb7 100644 --- a/include/linux/semaphore.h +++ b/include/linux/semaphore.h @@ -20,7 +20,7 @@ struct semaphore { #ifdef CONFIG_DETECT_HUNG_TASK_BLOCKER unsigned long last_holder; #endif -}; +} __aligned(4); /* For hung_task blocker tracking, which encodes type in LSBs */ #ifdef CONFIG_DETECT_HUNG_TASK_BLOCKER #define __LAST_HOLDER_SEMAPHORE_INITIALIZER \ -- 2.49.0