From mboxrd@z Thu Jan 1 00:00:00 1970 Received: from smtp.kernel.org (aws-us-west-2-korg-mail-alma10-1.taild15c8.ts.net [100.103.45.18]) (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 2C82A563298 for ; Tue, 8 Sep 2026 13:30:05 +0000 (UTC) Authentication-Results: smtp.subspace.kernel.org; arc=none smtp.client-ip=100.103.45.18 ARC-Seal:i=1; a=rsa-sha256; d=subspace.kernel.org; s=arc-20240116; t=1788874213; cv=none; b=Ow8ZN0J1vfBFXO0ijd58n2PP8c1kH/cHDW3Mmj48VfDllbjbnS3QUrB6tyt+JXzy2r/GJzzYxmuaZiQk+SlyM86NJihO+PZpBdoLgd0AbTFflB9KTgvOr8ez6Y6VR7VK+cGSGcyVLmCMh82AQfBeF9bBNJVwzq7JGIlnRwfCMZY= ARC-Message-Signature:i=1; a=rsa-sha256; d=subspace.kernel.org; s=arc-20240116; t=1788874213; c=relaxed/simple; bh=C6bqZNyT4o8d35HJtUsvvTHx7ibxT1AKZ/PErfJGUzg=; h=From:To:Cc:Subject:Date:Message-ID:In-Reply-To:References: MIME-Version; b=cCPw+4Cn/bilax40GYxnOkZG3QHV5XCC4mfyFKzjHHgEnV0EFHheow/c4M+ii9+9o/9WSSpl9+fZP6xEQ4OPcEcHkpDUCZ0iZwNJOkhybIGW39XcTrD0VTUS+OHWgnAHwLGs6JaLqpyVCpRq5woVIWHkltQoF0nb1uZCo4PJqDg= ARC-Authentication-Results:i=1; smtp.subspace.kernel.org; arc=none smtp.client-ip=100.103.45.18 Received: by smtp.kernel.org (Postfix) with ESMTPSA id 3D1851F00AC4; Tue, 8 Sep 2026 13:30:01 +0000 (UTC) From: Sasha Levin To: stable@vger.kernel.org Cc: Frederic Weisbecker , Peter Zijlstra , Thomas Gleixner , Neeraj Upadhyay , Uladzislau Rezki , Joel Fernandes , Boqun Feng , Nicolas Saenz Julienne , Marcelo Tosatti , Xiongfeng Wang , Yu Liao , Phil Auld , Paul Gortmaker , Alex Belits , "Paul E. McKenney" , Nicolas Saenz Julienne , Sasha Levin Subject: [PATCH 5.10.y 1/5] context_tracking: Add a note about noinstr VS unsafe context tracking functions Date: Tue, 8 Sep 2026 09:29:52 -0400 Message-ID: <20260908132958.2312212-1-sashal@kernel.org> X-Mailer: git-send-email 2.53.0 In-Reply-To: <2026090326-curtsy-rocket-6c6d@gregkh> References: <2026090326-curtsy-rocket-6c6d@gregkh> Precedence: bulk X-Mailing-List: stable@vger.kernel.org List-Id: List-Subscribe: List-Unsubscribe: MIME-Version: 1.0 Content-Transfer-Encoding: 8bit From: Frederic Weisbecker [ Upstream commit f67671baadf6dbae8eca46cb95e85b762e462b2b ] Some context tracking functions enter or exit into/from RCU idle mode while using trace-able and lockdep-aware IRQs (un-)masking. As a result those functions can't get tagged as noinstr. This is unlikely to be fixed since these are obsolete APIs. Drop a note about this matter. [ paulmck: Apply Peter Zijlstra feedback. ] Reported-by: Peter Zijlstra Cc: Peter Zijlstra Cc: Thomas Gleixner Cc: Neeraj Upadhyay Cc: Uladzislau Rezki Cc: Joel Fernandes Cc: Boqun Feng Cc: Nicolas Saenz Julienne Cc: Marcelo Tosatti Cc: Xiongfeng Wang Cc: Yu Liao Cc: Phil Auld Cc: Paul Gortmaker Cc: Alex Belits Signed-off-by: Frederic Weisbecker Signed-off-by: Paul E. McKenney Reviewed-by: Nicolas Saenz Julienne Tested-by: Nicolas Saenz Julienne Stable-dep-of: 7e8ee82e69fd ("ARM: 9477/1: Disable broken eBPF JIT on the Risc PC") Signed-off-by: Sasha Levin --- kernel/context_tracking.c | 34 ++++++++++++++++++++++++++++++++++ 1 file changed, 34 insertions(+) diff --git a/kernel/context_tracking.c b/kernel/context_tracking.c index 36a98c48aedc7..3082332f64765 100644 --- a/kernel/context_tracking.c +++ b/kernel/context_tracking.c @@ -103,6 +103,15 @@ void noinstr __context_tracking_enter(enum ctx_state state) } EXPORT_SYMBOL_GPL(__context_tracking_enter); +/* + * OBSOLETE: + * This function should be noinstr but the below local_irq_restore() is + * unsafe because it involves illegal RCU uses through tracing and lockdep. + * This is unlikely to be fixed as this function is obsolete. The preferred + * way is to call __context_tracking_enter() through user_enter_irqoff() + * or context_tracking_guest_enter(). It should be the arch entry code + * responsibility to call into context tracking with IRQs disabled. + */ void context_tracking_enter(enum ctx_state state) { unsigned long flags; @@ -125,6 +134,14 @@ void context_tracking_enter(enum ctx_state state) NOKPROBE_SYMBOL(context_tracking_enter); EXPORT_SYMBOL_GPL(context_tracking_enter); +/* + * OBSOLETE: + * This function should be noinstr but it unsafely calls local_irq_restore(), + * involving illegal RCU uses through tracing and lockdep. + * This is unlikely to be fixed as this function is obsolete. The preferred + * way is to call user_enter_irqoff(). It should be the arch entry code + * responsibility to call into context tracking with IRQs disabled. + */ void context_tracking_user_enter(void) { user_enter(); @@ -168,6 +185,15 @@ void noinstr __context_tracking_exit(enum ctx_state state) } EXPORT_SYMBOL_GPL(__context_tracking_exit); +/* + * OBSOLETE: + * This function should be noinstr but the below local_irq_save() is + * unsafe because it involves illegal RCU uses through tracing and lockdep. + * This is unlikely to be fixed as this function is obsolete. The preferred + * way is to call __context_tracking_exit() through user_exit_irqoff() + * or context_tracking_guest_exit(). It should be the arch entry code + * responsibility to call into context tracking with IRQs disabled. + */ void context_tracking_exit(enum ctx_state state) { unsigned long flags; @@ -182,6 +208,14 @@ void context_tracking_exit(enum ctx_state state) NOKPROBE_SYMBOL(context_tracking_exit); EXPORT_SYMBOL_GPL(context_tracking_exit); +/* + * OBSOLETE: + * This function should be noinstr but it unsafely calls local_irq_save(), + * involving illegal RCU uses through tracing and lockdep. This is unlikely + * to be fixed as this function is obsolete. The preferred way is to call + * user_exit_irqoff(). It should be the arch entry code responsibility to + * call into context tracking with IRQs disabled. + */ void context_tracking_user_exit(void) { user_exit(); -- 2.53.0