From nobody Fri Dec 19 15:19:26 2025 Received: from galois.linutronix.de (Galois.linutronix.de [193.142.43.55]) (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 6D58554648 for ; Tue, 27 Aug 2024 04:43:36 +0000 (UTC) Authentication-Results: smtp.subspace.kernel.org; arc=none smtp.client-ip=193.142.43.55 ARC-Seal: i=1; a=rsa-sha256; d=subspace.kernel.org; s=arc-20240116; t=1724733818; cv=none; b=sUSyrF2hmX2eHJ2zRAqM8YEsQahc9+lAr/HRPG1TYaJTnLqXxXIQHssgidHfKiu6gavozZFBXGhhYHFey7T7KbZrWO0/x2zrzRI/Ih70Snqkww+5X5gQVB9JrvZlQxWRNYg2z3HKwCcKDsKv0Bo2TZVeOSPbuu9c+Aic7tyC90I= ARC-Message-Signature: i=1; a=rsa-sha256; d=subspace.kernel.org; s=arc-20240116; t=1724733818; c=relaxed/simple; bh=WxJn38aQwzgVssvSr9SkazK1C6E06LBK31hfQqtQBiE=; h=From:To:Cc:Subject:Date:Message-Id:In-Reply-To:References: MIME-Version; b=uenkWgXngf5GxYlGEMZo0FErUIt5TKGeArUt2Pt7ALxr9iXvKzLjNA89ucsLaP9A+C5bsWKJb53JIXl2X06q8YoWLh2lm2HQ4YcaEUx9TE7dX6se38hN/6KEBbqx0LEpq01RWq2hz7lYsV1UMPm7H5STNtrZDM4OFeFy9r+twR4= ARC-Authentication-Results: i=1; smtp.subspace.kernel.org; dmarc=pass (p=none dis=none) header.from=linutronix.de; spf=pass smtp.mailfrom=linutronix.de; dkim=pass (2048-bit key) header.d=linutronix.de header.i=@linutronix.de header.b=1PSLr6ji; dkim=permerror (0-bit key) header.d=linutronix.de header.i=@linutronix.de header.b=BRULf9li; arc=none smtp.client-ip=193.142.43.55 Authentication-Results: smtp.subspace.kernel.org; dmarc=pass (p=none dis=none) header.from=linutronix.de Authentication-Results: smtp.subspace.kernel.org; spf=pass smtp.mailfrom=linutronix.de Authentication-Results: smtp.subspace.kernel.org; dkim=pass (2048-bit key) header.d=linutronix.de header.i=@linutronix.de header.b="1PSLr6ji"; dkim=permerror (0-bit key) header.d=linutronix.de header.i=@linutronix.de header.b="BRULf9li" From: John Ogness DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=linutronix.de; s=2020; t=1724733814; h=from:from:reply-to:subject:subject:date:date:message-id:message-id: to:to:cc:cc:mime-version:mime-version: content-transfer-encoding:content-transfer-encoding: in-reply-to:in-reply-to:references:references; bh=J912AwN71BiOtVlEylsZ3qn7Oo+IxLpwqnkVptIsJ08=; b=1PSLr6jiNFs3S/tun844IZrN3cBlnbijOvQpF2KFGnD7IJQWq2CrH1hqs38/UYUmMKZy9Q NKMEVF+iU5ge78jp8lO7xchsde621nG8NWerGA2gC6wgJ0YElroEyzKE5PZ7LB7XKXHZO5 d8Qvf2wwuSyvND2lFaiLrLQHPDAoSxzbjzyCFbHZMr5A+rVnVT4+To3r4XpIxq3udNN8H5 KCUAWDB0Bg1OXmuczmppJJhyRUn0eoR0XHRFSX+pkl1QrD+LYJSS+T3bYJDDeuDY57bFQz 1cGlySssPv/BkGIIjzjst71xZXlXb9jsGYL6z6Bev3kHj/PYgKtmfpjQE/TUCw== DKIM-Signature: v=1; a=ed25519-sha256; c=relaxed/relaxed; d=linutronix.de; s=2020e; t=1724733814; h=from:from:reply-to:subject:subject:date:date:message-id:message-id: to:to:cc:cc:mime-version:mime-version: content-transfer-encoding:content-transfer-encoding: in-reply-to:in-reply-to:references:references; bh=J912AwN71BiOtVlEylsZ3qn7Oo+IxLpwqnkVptIsJ08=; b=BRULf9lix9z0aTjTh2pxjzZFyKfjCXmu6DhpHXz6e406EoUZrvSqGgb0ii7T6TQ7B9rHzu 8P7bjg/aBAn6KSDg== To: Petr Mladek Cc: Sergey Senozhatsky , Steven Rostedt , Thomas Gleixner , linux-kernel@vger.kernel.org Subject: [PATCH printk v4 02/17] printk: Fail pr_flush() if before SYSTEM_SCHEDULING Date: Tue, 27 Aug 2024 06:49:18 +0206 Message-Id: <20240827044333.88596-3-john.ogness@linutronix.de> In-Reply-To: <20240827044333.88596-1-john.ogness@linutronix.de> References: <20240827044333.88596-1-john.ogness@linutronix.de> 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" A follow-up change adds pr_flush() to console unregistration. However, with boot consoles unregistration can happen very early if there are also regular consoles registering as well. In this case the pr_flush() is not important because all consoles are flushed when checking the initial console sequence number. Allow pr_flush() to fail if @system_state has not yet reached SYSTEM_SCHEDULING. This avoids might_sleep() and msleep() explosions that would otherwise occur: [ 0.436739][ T0] printk: legacy console [ttyS0] enabled [ 0.439820][ T0] printk: legacy bootconsole [earlyser0] disabled [ 0.446822][ T0] BUG: scheduling while atomic: swapper/0/0/0x00000002 [ 0.450491][ T0] 1 lock held by swapper/0/0: [ 0.457897][ T0] #0: ffffffff82ae5f88 (console_mutex){+.+.}-{4:4}, a= t: console_list_lock+0x20/0x70 [ 0.463141][ T0] Modules linked in: [ 0.465307][ T0] CPU: 0 PID: 0 Comm: swapper/0 Not tainted 6.10.0-rc1= + #372 [ 0.469394][ T0] Hardware name: QEMU Standard PC (i440FX + PIIX, 1996= ), BIOS 1.14.0-2 04/01/2014 [ 0.474402][ T0] Call Trace: [ 0.476246][ T0] [ 0.481473][ T0] dump_stack_lvl+0x93/0xb0 [ 0.483949][ T0] dump_stack+0x10/0x20 [ 0.486256][ T0] __schedule_bug+0x68/0x90 [ 0.488753][ T0] __schedule+0xb9b/0xd80 [ 0.491179][ T0] ? lock_release+0xb5/0x270 [ 0.493732][ T0] schedule+0x43/0x170 [ 0.495998][ T0] schedule_timeout+0xc5/0x1e0 [ 0.498634][ T0] ? __pfx_process_timeout+0x10/0x10 [ 0.501522][ T0] ? msleep+0x13/0x50 [ 0.503728][ T0] msleep+0x3c/0x50 [ 0.505847][ T0] __pr_flush.constprop.0.isra.0+0x56/0x500 [ 0.509050][ T0] ? _printk+0x58/0x80 [ 0.511332][ T0] ? lock_is_held_type+0x9c/0x110 [ 0.514106][ T0] unregister_console_locked+0xe1/0x450 [ 0.517144][ T0] register_console+0x509/0x620 [ 0.519827][ T0] ? __pfx_univ8250_console_init+0x10/0x10 [ 0.523042][ T0] univ8250_console_init+0x24/0x40 [ 0.525845][ T0] console_init+0x43/0x210 [ 0.528280][ T0] start_kernel+0x493/0x980 [ 0.530773][ T0] x86_64_start_reservations+0x18/0x30 [ 0.533755][ T0] x86_64_start_kernel+0xae/0xc0 [ 0.536473][ T0] common_startup_64+0x12c/0x138 [ 0.539210][ T0] And then the kernel goes into an infinite loop complaining about: 1. releasing a pinned lock 2. unpinning an unpinned lock 3. bad: scheduling from the idle thread! 4. goto 1 Signed-off-by: John Ogness Reviewed-by: Petr Mladek --- kernel/printk/printk.c | 4 ++++ 1 file changed, 4 insertions(+) diff --git a/kernel/printk/printk.c b/kernel/printk/printk.c index 6accd1704e73..acf668001096 100644 --- a/kernel/printk/printk.c +++ b/kernel/printk/printk.c @@ -3991,6 +3991,10 @@ static bool __pr_flush(struct console *con, int time= out_ms, bool reset_on_progre u64 diff; u64 seq; =20 + /* Sorry, pr_flush() will not work this early. */ + if (system_state < SYSTEM_SCHEDULING) + return false; + might_sleep(); =20 seq =3D prb_next_reserve_seq(prb); --=20 2.39.2