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 E57D419F473; Thu, 15 Aug 2024 14:24:31 +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=1723731872; cv=none; b=QglxiYbSD3x8nThJruQ5/tiUU6JWXqC3jTlyq3WPXhyv6NN/iVnt0b0AEk90mTL0H1Ei04+n8ecWj5Ut+YNcOfqEssyKR4Socfq97qqbJ62aiiiqb09nlowWgdbfeIlSaTbt1uPQl8J6vqHYZOXcm6iRM4ZTr4WNEuXjGy9KIzc= ARC-Message-Signature:i=1; a=rsa-sha256; d=subspace.kernel.org; s=arc-20240116; t=1723731872; c=relaxed/simple; bh=XRCplMXi57a1UbsEGAsWnoN9I4wmbJAgQfyqfVK3oBA=; h=From:To:Cc:Subject:Date:Message-ID:In-Reply-To:References: MIME-Version; b=kT3lmWJ3KPre5ME/UEFpydjctDqu/2MA+Kub5zlC8OfTN8lmqAkCvrBA231WWiit+G5NVqyTiq6PIhwkzCIYOAsbn2r+n0X8jS4Bj+ylWh7KsEZb2JV3fR83IrGnSYhT8+M2AjLCFC65zonqbZEkgsQS4FjAigrXKHZjPpmQzgs= ARC-Authentication-Results:i=1; smtp.subspace.kernel.org; dkim=pass (1024-bit key) header.d=linuxfoundation.org header.i=@linuxfoundation.org header.b=p1+k2Cpy; arc=none smtp.client-ip=10.30.226.201 Authentication-Results: smtp.subspace.kernel.org; dkim=pass (1024-bit key) header.d=linuxfoundation.org header.i=@linuxfoundation.org header.b="p1+k2Cpy" Received: by smtp.kernel.org (Postfix) with ESMTPSA id 6BAB4C32786; Thu, 15 Aug 2024 14:24:31 +0000 (UTC) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/simple; d=linuxfoundation.org; s=korg; t=1723731871; bh=XRCplMXi57a1UbsEGAsWnoN9I4wmbJAgQfyqfVK3oBA=; h=From:To:Cc:Subject:Date:In-Reply-To:References:From; b=p1+k2CpyTffQws1Va3AlzwHBMD0ZWiD55rhYk1Og66kgCMw4+/Dq4THag5Y6reChr l8ZXOIOlQG9guWkftCZEzfap3ULUn+wY+gOp652ouU/TlaHEyDW4oL5LFaHYEXbRBH H89vtVVBXqrmRH7i8eKn5G/Zt+18TToz2nT3m8eA= From: Greg Kroah-Hartman To: stable@vger.kernel.org Cc: Greg Kroah-Hartman , patches@lists.linux.dev, David Wang <00107082@163.com>, Thomas Gleixner , Yu Liao Subject: [PATCH 5.4 235/259] tick/broadcast: Move per CPU pointer access into the atomic section Date: Thu, 15 Aug 2024 15:26:08 +0200 Message-ID: <20240815131911.850207006@linuxfoundation.org> X-Mailer: git-send-email 2.46.0 In-Reply-To: <20240815131902.779125794@linuxfoundation.org> References: <20240815131902.779125794@linuxfoundation.org> User-Agent: quilt/0.67 X-stable: review X-Patchwork-Hint: ignore Precedence: bulk X-Mailing-List: stable@vger.kernel.org List-Id: List-Subscribe: List-Unsubscribe: MIME-Version: 1.0 Content-Transfer-Encoding: 8bit 5.4-stable review patch. If anyone has any objections, please let me know. ------------------ From: Thomas Gleixner commit 6881e75237a84093d0986f56223db3724619f26e upstream. The recent fix for making the take over of the broadcast timer more reliable retrieves a per CPU pointer in preemptible context. This went unnoticed as compilers hoist the access into the non-preemptible region where the pointer is actually used. But of course it's valid that the compiler keeps it at the place where the code puts it which rightfully triggers: BUG: using smp_processor_id() in preemptible [00000000] code: caller is hotplug_cpu__broadcast_tick_pull+0x1c/0xc0 Move it to the actual usage site which is in a non-preemptible region. Fixes: f7d43dd206e7 ("tick/broadcast: Make takeover of broadcast hrtimer reliable") Reported-by: David Wang <00107082@163.com> Signed-off-by: Thomas Gleixner Tested-by: Yu Liao Cc: stable@vger.kernel.org Link: https://lore.kernel.org/all/87ttg56ers.ffs@tglx Signed-off-by: Greg Kroah-Hartman --- kernel/time/tick-broadcast.c | 3 ++- 1 file changed, 2 insertions(+), 1 deletion(-) --- a/kernel/time/tick-broadcast.c +++ b/kernel/time/tick-broadcast.c @@ -944,7 +944,6 @@ void tick_broadcast_switch_to_oneshot(vo #ifdef CONFIG_HOTPLUG_CPU void hotplug_cpu__broadcast_tick_pull(int deadcpu) { - struct tick_device *td = this_cpu_ptr(&tick_cpu_device); struct clock_event_device *bc; unsigned long flags; @@ -970,6 +969,8 @@ void hotplug_cpu__broadcast_tick_pull(in * device to avoid the starvation. */ if (tick_check_broadcast_expired()) { + struct tick_device *td = this_cpu_ptr(&tick_cpu_device); + cpumask_clear_cpu(smp_processor_id(), tick_broadcast_force_mask); tick_program_event(td->evtdev->next_event, 1); }