From nobody Wed Dec 17 08:58:10 2025 Received: from mx1.riseup.net (mx1.riseup.net [198.252.153.129]) (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 5F4C01AA1E0 for ; Thu, 27 Mar 2025 23:44:08 +0000 (UTC) Authentication-Results: smtp.subspace.kernel.org; arc=none smtp.client-ip=198.252.153.129 ARC-Seal: i=1; a=rsa-sha256; d=subspace.kernel.org; s=arc-20240116; t=1743119050; cv=none; b=F4n+5P8rG5kIGbYJq1kQjzm5EC4epmCA7BA3G8nBMhYamWVxq23F2JtrY1LPdQqHV3YT7hBad1DeWGChQJ5z9C8mDBt65HCsHtmEyLm2IwcJgGXh5vJ//Jy1fnVSvPvnAN9cbJ1PWlwhNUGKKZjwaHZ9CifBvB/+okWqBI74BZs= ARC-Message-Signature: i=1; a=rsa-sha256; d=subspace.kernel.org; s=arc-20240116; t=1743119050; c=relaxed/simple; bh=alf3U4GcHSVeqmFlbDvuq5reIBuvm9agxUeKx/4y55g=; h=From:To:Cc:Subject:Date:Message-ID:MIME-Version; b=i3NaYp8E7qf0lyCfQ+Uy+k/nw8iZL44KaSW1/Mf9RIZrXfZPo1U3eJ3jTIQngu9gRY6UiA6BpUDJ0hxOq5PfEv34fEgI9bcIF7t61F7l/mNbJ4WvHqJwKcHfFtmYY8NcSRYAfRC6QFngY1tg6iFoiHBJM4YlRXA1APibiIkYUx0= ARC-Authentication-Results: i=1; smtp.subspace.kernel.org; dmarc=pass (p=none dis=none) header.from=riseup.net; spf=pass smtp.mailfrom=riseup.net; dkim=pass (1024-bit key) header.d=riseup.net header.i=@riseup.net header.b=VlufetNz; arc=none smtp.client-ip=198.252.153.129 Authentication-Results: smtp.subspace.kernel.org; dmarc=pass (p=none dis=none) header.from=riseup.net Authentication-Results: smtp.subspace.kernel.org; spf=pass smtp.mailfrom=riseup.net Authentication-Results: smtp.subspace.kernel.org; dkim=pass (1024-bit key) header.d=riseup.net header.i=@riseup.net header.b="VlufetNz" Received: from fews02-sea.riseup.net (fews02-sea-pn.riseup.net [10.0.1.112]) (using TLSv1.3 with cipher TLS_AES_256_GCM_SHA384 (256/256 bits) key-exchange X25519 server-signature RSA-PSS (2048 bits) server-digest SHA256) (No client certificate requested) by mx1.riseup.net (Postfix) with ESMTPS id 4ZP0c740lGzDqVm; Thu, 27 Mar 2025 23:44:07 +0000 (UTC) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/simple; d=riseup.net; s=squak; t=1743119047; bh=alf3U4GcHSVeqmFlbDvuq5reIBuvm9agxUeKx/4y55g=; h=From:To:Cc:Subject:Date:From; b=VlufetNzwXU8NRcUODo7oGdFcHs8Cw+lmJ6fnJXrXemx7ckgsXDJm2/o35jEoxOOL 5VTc0efTvMQfBHjp0jc/xBpKSBgBpazFi7eIw4vCLQj+9LNmWgZ68xIfstaSYH+8J7 OoA3qeAJzbdEXyO2rPK8rPxSCfDs6KTFhEzn/jyc= X-Riseup-User-ID: AA98FD0A338178116BF02F5E8D8EB66630877B08DD781AD6E5F015046AD33AE9 Received: from [127.0.0.1] (localhost [127.0.0.1]) by fews02-sea.riseup.net (Postfix) with ESMTPSA id 4ZP0c54WQZzFwfR; Thu, 27 Mar 2025 23:44:05 +0000 (UTC) From: Fernando Fernandez Mancera To: x86@kernel.org, tglx@linutronix.de, linux-kernel@vger.kernel.org Cc: dwmw@amazon.co.uk, mhkelley@outlook.com, mingo@kernel.org, Fernando Fernandez Mancera Subject: [PATCH v3] x86/i8253: Invoke clockevent_i8253_disable() with interrupts disabled Date: Fri, 28 Mar 2025 00:43:57 +0100 Message-ID: <20250327234357.3383-1-ffmancera@riseup.net> Precedence: bulk X-Mailing-List: linux-kernel@vger.kernel.org List-Id: List-Subscribe: List-Unsubscribe: MIME-Version: 1.0 Content-Transfer-Encoding: quoted-printable Content-Type: text/plain; charset="utf-8" Lockdep complains correctly due to the context, but in reality there is no possible deadlock. At the point where pit_timer_init() is called there is no other possible usage of i8253_lock because the system is still in the very early boot stage. pit_timer_init() should disable interrupts before calling clockevent_i8253_disable() and do not inflict the raw_spin_lock_irqsave() on the callback function. This prevents lockdep from detecting a false positive and future proves the code. [ 45.408952] =3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D= =3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D= =3D=3D=3D=3D=3D=3D=3D=3D [ 45.408970] WARNING: HARDIRQ-safe -> HARDIRQ-unsafe lock order detected [ 45.408974] 6.14.0-rc7+ #6 Not tainted [ 45.408978] ----------------------------------------------------- [ 45.408980] systemd-sleep/3324 [HC0[0]:SC0[0]:HE0:SE1] is trying to acqu= ire: [ 45.408986] ffffffffb2c23398 (i8253_lock){+.+.}-{2:2}, at: pcspkr_event+= 0x3f/0xe0 [pcspkr] [ 45.409004] and this task is already holding: [ 45.409006] ffff9c334d7c2230 (&dev->event_lock){-.-.}-{3:3}, at: input_d= ev_resume+0x21/0x50 [ 45.409023] which would create a new lock dependency: [ 45.409025] (&dev->event_lock){-.-.}-{3:3} -> (i8253_lock){+.+.}-{2:2} [ 45.409043] but this new dependency connects a HARDIRQ-irq-safe lock: [ 45.409045] (&dev->event_lock){-.-.}-{3:3} [ 45.409052] ... which became HARDIRQ-irq-safe at: [ 45.409055] lock_acquire+0xd0/0x2f0 [ 45.409062] _raw_spin_lock_irqsave+0x48/0x70 [ 45.409067] input_event+0x3c/0x80 [ 45.409071] atkbd_receive_byte+0x9b/0x6e0 [ 45.409077] ps2_interrupt+0xb2/0x1d0 [ 45.409082] serio_interrupt+0x4a/0x90 [ 45.409087] i8042_handle_data+0xf8/0x280 [ 45.409091] i8042_interrupt+0x11/0x40 [ 45.409095] __handle_irq_event_percpu+0x87/0x260 [ 45.409100] handle_irq_event+0x38/0x90 [ 45.409105] handle_edge_irq+0x8b/0x230 [ 45.409109] __common_interrupt+0x5c/0x120 [ 45.409114] common_interrupt+0x80/0xa0 [ 45.409120] asm_common_interrupt+0x26/0x40 [ 45.409125] pv_native_safe_halt+0xf/0x20 [ 45.409130] default_idle+0x9/0x20 [ 45.409135] default_idle_call+0x7a/0x1d0 [ 45.409140] do_idle+0x215/0x260 [ 45.409144] cpu_startup_entry+0x29/0x30 [ 45.409149] start_secondary+0x132/0x170 [ 45.409153] common_startup_64+0x13e/0x141 [ 45.409158] to a HARDIRQ-irq-unsafe lock: [ 45.409161] (i8253_lock){+.+.}-{2:2} [ 45.409167] ... which became HARDIRQ-irq-unsafe at: [ 45.409170] ... [ 45.409172] lock_acquire+0xd0/0x2f0 [ 45.409177] _raw_spin_lock+0x30/0x40 [ 45.409181] clockevent_i8253_disable+0x1c/0x60 [ 45.409186] pit_timer_init+0x25/0x50 [ 45.409191] hpet_time_init+0x46/0x50 [ 45.409196] x86_late_time_init+0x1b/0x40 [ 45.409201] start_kernel+0x962/0xa00 [ 45.409206] x86_64_start_reservations+0x24/0x30 [ 45.409211] x86_64_start_kernel+0xed/0xf0 [ 45.409215] common_startup_64+0x13e/0x141 [ 45.409220] other info that might help us debug this: [ 45.409222] Possible interrupt unsafe locking scenario: [ 45.409224] CPU0 CPU1 [ 45.409226] ---- ---- [ 45.409228] lock(i8253_lock); [ 45.409234] local_irq_disable(); [ 45.409237] lock(&dev->event_lock); [ 45.409243] lock(i8253_lock); [ 45.409249] [ 45.409251] lock(&dev->event_lock); [ 45.409257] *** DEADLOCK *** Signed-off-by: Fernando Fernandez Mancera --- v1: initial patch v2: use local_irq_save()/restore() around clockevent_i8253_disable() v3: improve wording of commit message, dropped "Fixes" tag and used scoped_guard(irq) instead. --- arch/x86/kernel/i8253.c | 3 ++- 1 file changed, 2 insertions(+), 1 deletion(-) diff --git a/arch/x86/kernel/i8253.c b/arch/x86/kernel/i8253.c index 80e262bb627f..cb9852ad6098 100644 --- a/arch/x86/kernel/i8253.c +++ b/arch/x86/kernel/i8253.c @@ -46,7 +46,8 @@ bool __init pit_timer_init(void) * VMMs otherwise steal CPU time just to pointlessly waggle * the (masked) IRQ. */ - clockevent_i8253_disable(); + scoped_guard(irq) + clockevent_i8253_disable(); return false; } clockevent_i8253_init(true); --=20 2.49.0