From mboxrd@z Thu Jan 1 00:00:00 1970 Received: from smtp.kernel.org (aws-us-west-2-korg-mail-1.web.codeaurora.org [10.30.226.201]) (using TLSv1.2 with cipher ECDHE-RSA-AES256-GCM-SHA384 (256/256 bits)) (No client certificate requested) by smtp.subspace.kernel.org (Postfix) with ESMTPS id 2249A2B9B9; Tue, 9 Sep 2025 23:33:50 +0000 (UTC) Authentication-Results: smtp.subspace.kernel.org; arc=none smtp.client-ip=10.30.226.201 ARC-Seal:i=1; a=rsa-sha256; d=subspace.kernel.org; s=arc-20240116; t=1757460830; cv=none; b=YuURIfE7geK/nFUrlEPq8wT+29MjHLSzAOYYcV3VA1f++z6FyAKKh2sviS5vcyCMqF99M3Qwtbzmn6vdq5rwuNXfb3pCgeIUd5zLnrY+K5YNnldcGhyNjqQvSbeKltjCeXSY78bVyt4aGJNfsM709EgGgsklJuNvbgN39Zh/fRA= ARC-Message-Signature:i=1; a=rsa-sha256; d=subspace.kernel.org; s=arc-20240116; t=1757460830; c=relaxed/simple; bh=AxtQAct7EO/T+fTTMJ0larcBPKpKVcBsnKR0WxsF2ts=; h=Date:To:From:Subject:Message-Id; b=HAwRst/BxNfOxGZ/kLAYbGHT3GP/D5o6Hm8Hr+VqMdSi4XP8UuzqdOgy6LZLETo9ntr7V2aK35wciX9HSs6s55MChcZXHbPnM7GU4DujfzjSmqzqDPZzhx9A8IiJWf9EXHb2BTfkNeUWZ0zmQOA0015zRpPnzbs0kF2cXOOG2y0= ARC-Authentication-Results:i=1; smtp.subspace.kernel.org; dkim=pass (1024-bit key) header.d=linux-foundation.org header.i=@linux-foundation.org header.b=jK8/N6Me; arc=none smtp.client-ip=10.30.226.201 Authentication-Results: smtp.subspace.kernel.org; dkim=pass (1024-bit key) header.d=linux-foundation.org header.i=@linux-foundation.org header.b="jK8/N6Me" Received: by smtp.kernel.org (Postfix) with ESMTPSA id D2FC9C4CEF4; Tue, 9 Sep 2025 23:33:49 +0000 (UTC) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/simple; d=linux-foundation.org; s=korg; t=1757460829; bh=AxtQAct7EO/T+fTTMJ0larcBPKpKVcBsnKR0WxsF2ts=; h=Date:To:From:Subject:From; b=jK8/N6Me5ebsYx563hYWAs1eV2ZljpBzsf1+ZwQxKFalRn3o2AJW1AIBliEw6mb7A aqFwre1nW4g9QPS6qsnhjXTYg5VKNKncB3DwhBlWQIvVPKZdnBIZqRNxwQctVlcdv5 /3p1a0/DS1EpExnw4RowfWL1BI6t3F/++W4+CEkY= Date: Tue, 09 Sep 2025 16:33:49 -0700 To: mm-commits@vger.kernel.org,will@kernel.org,tfiga@chromium.org,stable@vger.kernel.org,senozhatsky@chromium.org,rostedt@goodmis.org,peterz@infradead.org,oak@helsinkinet.fi,mingzhe.yang@ly.com,mingo@redhat.com,mhiramat@kernel.org,longman@redhat.com,leonylgao@tencent.com,kent.overstreet@linux.dev,jstultz@google.com,joel.granados@kernel.org,glaubitz@physik.fu-berlin.de,geert@linux-m68k.org,fthain@linux-m68k.org,boqun.feng@gmail.com,anna.schumaker@oracle.com,lance.yang@linux.dev,akpm@linux-foundation.org From: Andrew Morton Subject: + hung_task-fix-warnings-caused-by-unaligned-lock-pointers.patch added to mm-hotfixes-unstable branch Message-Id: <20250909233349.D2FC9C4CEF4@smtp.kernel.org> Precedence: bulk X-Mailing-List: stable@vger.kernel.org List-Id: List-Subscribe: List-Unsubscribe: The patch titled Subject: hung_task: fix warnings caused by unaligned lock pointers has been added to the -mm mm-hotfixes-unstable branch. Its filename is hung_task-fix-warnings-caused-by-unaligned-lock-pointers.patch This patch will shortly appear at https://git.kernel.org/pub/scm/linux/kernel/git/akpm/25-new.git/tree/patches/hung_task-fix-warnings-caused-by-unaligned-lock-pointers.patch This patch will later appear in the mm-hotfixes-unstable branch at git://git.kernel.org/pub/scm/linux/kernel/git/akpm/mm Before you just go and hit "reply", please: a) Consider who else should be cc'ed b) Prefer to cc a suitable mailing list as well c) Ideally: find the original patch on the mailing list and do a reply-to-all to that, adding suitable additional cc's *** Remember to use Documentation/process/submit-checklist.rst when testing your code *** The -mm tree is included into linux-next via the mm-everything branch at git://git.kernel.org/pub/scm/linux/kernel/git/akpm/mm and is updated there every 2-3 working days ------------------------------------------------------ From: Lance Yang Subject: hung_task: fix warnings caused by unaligned lock pointers Date: Tue, 9 Sep 2025 22:52:43 +0800 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 Eero Tamminen, 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, the runtime checks are adjusted to silently ignore any lock that is not 4-byte aligned, effectively disabling the feature in such cases and avoiding the related warnings. Thanks to Geert Uytterhoeven for bisecting! Link: https://lkml.kernel.org/r/20250909145243.17119-1-lance.yang@linux.dev Fixes: e711faaafbe5 ("hung_task: replace blocker_mutex with encoded blocker") Signed-off-by: Lance Yang Reported-by: Eero Tamminen Closes: https://lore.kernel.org/lkml/CAMuHMdW7Ab13DdGs2acMQcix5ObJK0O2dG_Fxzr8_g58Rc1_0g@mail.gmail.com Reviewed-by: Masami Hiramatsu (Google) Cc: John Paul Adrian Glaubitz Cc: Anna Schumaker Cc: Boqun Feng Cc: Finn Thain Cc: Geert Uytterhoeven Cc: Ingo Molnar Cc: Joel Granados Cc: John Stultz Cc: Kent Overstreet Cc: Lance Yang Cc: Mingzhe Yang Cc: Peter Zijlstra Cc: Sergey Senozhatsky Cc: Steven Rostedt Cc: Tomasz Figa Cc: Waiman Long Cc: Will Deacon Cc: Yongliang Gao Cc: Signed-off-by: Andrew Morton --- include/linux/hung_task.h | 8 +++++--- 1 file changed, 5 insertions(+), 3 deletions(-) --- a/include/linux/hung_task.h~hung_task-fix-warnings-caused-by-unaligned-lock-pointers +++ a/include/linux/hung_task.h @@ -20,6 +20,10 @@ * always zero. So we can use these bits to encode the specific blocking * type. * + * Note that on architectures where this is not guaranteed, or for any + * unaligned lock, this tracking mechanism is silently skipped for that + * lock. + * * Type encoding: * 00 - Blocked on mutex (BLOCKER_TYPE_MUTEX) * 01 - Blocked on semaphore (BLOCKER_TYPE_SEM) @@ -45,7 +49,7 @@ static inline void hung_task_set_blocker * If the lock pointer matches the BLOCKER_TYPE_MASK, return * without writing anything. */ - if (WARN_ON_ONCE(lock_ptr & BLOCKER_TYPE_MASK)) + if (lock_ptr & BLOCKER_TYPE_MASK) return; WRITE_ONCE(current->blocker, lock_ptr | type); @@ -53,8 +57,6 @@ static inline void hung_task_set_blocker static inline void hung_task_clear_blocker(void) { - WARN_ON_ONCE(!READ_ONCE(current->blocker)); - WRITE_ONCE(current->blocker, 0UL); } _ Patches currently in -mm which might be from lance.yang@linux.dev are maintainers-add-lance-yang-as-a-thp-reviewer.patch hung_task-fix-warnings-caused-by-unaligned-lock-pointers.patch mm-skip-mlocked-thps-that-are-underused-early-in-deferred_split_scan.patch