From mboxrd@z Thu Jan 1 00:00:00 1970 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 01FC61487D0; Fri, 2 Feb 2024 17:02:32 +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=1706893354; cv=none; b=jUVbQmEggjkjPGVRRiPjM7wSmaOCNUy7wesV9RxYxWxcyJ96z3QMTclLya/eJJ1gg4vZLZaJFW9hpC88SZFCnKXSb1Jf5uRB8brSY1jCtoj8CCyxM/7ZXWPgjPRVnKz09J2V3zY1aaYXDxZh34uNgsAQcgEnr3yFFwGYWgY0oHo= ARC-Message-Signature:i=1; a=rsa-sha256; d=subspace.kernel.org; s=arc-20240116; t=1706893354; c=relaxed/simple; bh=KoX8uvs6sRAFq3Wu/LCxCrn4njxS++aM7O+B0NSHNog=; h=From:To:Cc:Subject:In-Reply-To:References:Date:Message-ID: MIME-Version:Content-Type; b=PtjAzI7wxKq/Cq1dpX8t0snWqnZR+RKRXosba2IV69XlIn+RvfQ+RZtGpNDiYVlLzT3KKodvtD3E25DWh+xQJZa1WV3o91C++00CeZfHL/fNXWGptIkMMOtf1yiyDXgufcjno4xpJ0QqqHdPU8OSPQ8iqmuVdfpjRVir3o24a+c= 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=cMJIXxyu; dkim=permerror (0-bit key) header.d=linutronix.de header.i=@linutronix.de header.b=dHqg+SZw; 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="cMJIXxyu"; dkim=permerror (0-bit key) header.d=linutronix.de header.i=@linutronix.de header.b="dHqg+SZw" From: John Ogness DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=linutronix.de; s=2020; t=1706893351; h=from:from:reply-to:subject:subject:date:date:message-id:message-id: to:to:cc:cc:mime-version:mime-version:content-type:content-type: in-reply-to:in-reply-to:references:references; bh=1UyVSWbQkjqdlMyzs2zo2iOAjvlC5wSsBEpWz41rzt8=; b=cMJIXxyu3FpXaPwttxUh05Hh+nhzyRTB4D0oE+vmhuAvAMuykBxvo35/XrIf9s6KL4mMrk f5JicRFyVO3XhZL5bBDyzuogKloWdsq0IdGjf/IG5lyCXYl3WvGwq5+zzrJwdk/1dapvHK RkRv4q8JQKXwx6o+NWyap6baBaMiuccpor1la4mlJ6RaQUlW0z9EOk7A06JCOfrEhzUB1v Reca1LorwafHL6429hzmM3tq428ytBATxPjP3pz7mni/msnuGEBstyzTbvlJOzDRlq2xsX mbPRf/dOCWeUcbQW59cY2IDeEDNubFUWYx3qj/4qogskj77NmroAaBi1c09mvg== DKIM-Signature: v=1; a=ed25519-sha256; c=relaxed/relaxed; d=linutronix.de; s=2020e; t=1706893351; h=from:from:reply-to:subject:subject:date:date:message-id:message-id: to:to:cc:cc:mime-version:mime-version:content-type:content-type: in-reply-to:in-reply-to:references:references; bh=1UyVSWbQkjqdlMyzs2zo2iOAjvlC5wSsBEpWz41rzt8=; b=dHqg+SZwoxX+61PGRb+zoPhE99YYjNw6ZFYkAvMVeH12Ie5tb8vONXsRhnl2ODZwTes7lG NBKClq6VpuD9LEDg== To: paulmck@kernel.org Cc: Tejun Heo , Lai Jiangshan , Petr Mladek , Steven Rostedt , Sergey Senozhatsky , Stephen Rothwell , linux-kernel@vger.kernel.org, rcu@vger.kernel.org Subject: Re: [BUG] workqueues and printk not playing nice since next-20240130 In-Reply-To: <7b5a386e-2dcf-49f1-a8e9-c46d2a9f8800@paulmck-laptop> References: <410d6a87-bf34-457e-b714-1e6149d48532@paulmck-laptop> <87le83ara7.fsf@jogness.linutronix.de> <7b5a386e-2dcf-49f1-a8e9-c46d2a9f8800@paulmck-laptop> Date: Fri, 02 Feb 2024 18:08:25 +0106 Message-ID: <87zfwibxzy.fsf@jogness.linutronix.de> Precedence: bulk X-Mailing-List: linux-kernel@vger.kernel.org List-Id: List-Subscribe: List-Unsubscribe: MIME-Version: 1.0 Content-Type: text/plain On 2024-02-02, "Paul E. McKenney" wrote: >> The printk ringbuffer contents would certainly be interesting. >> >> If you build the GDB scripts (CONFIG_GDB_SCRIPTS) then you will have: >> >> (gdb) lx-dmesg > > This says no such command even though I do have CONFIG_GDB_SCRIPTS=y > in my .config. You actually need to build them as well. The target is "scripts_gdb" And you probably need to add: add-auto-load-safe-path /path/to/your/kernel/build/directory to your .gdbinit (This is documented in Documentation/dev-tools/gdb-kernel-debugging.rst) >> As an alternative, you could copy the contents of >> Documentation/admin-guide/kdump/gdbmacros.txt into your .gdbinit and >> then will have: >> >> (gdb) dmesg > > This one hangs. :-/ I will look into this. > On the other hand, next-20240202 doesn't show the problem. No idea > what might have changed. :-/ Did you check the backtrace on all the "threads"? I would expect one of them has tty in it and is probably deadlocked. There are known problems that if a WARN or lockdep triggers while holding the port lock, that CPU will deadlock itself. That has the effect that no output is generated, but all the other CPUs will run fine. And even printk() calls will happily store into the ringbuffer because they use trylock for printing and the deadlocked CPU will be holding the lock. John