From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: X-Spam-Checker-Version: SpamAssassin 3.4.0 (2014-02-07) on aws-us-west-2-korg-lkml-1.web.codeaurora.org X-Spam-Level: X-Spam-Status: No, score=-0.8 required=3.0 tests=DKIM_SIGNED,DKIM_VALID, DKIM_VALID_AU,HEADER_FROM_DIFFERENT_DOMAINS,MAILING_LIST_MULTI,SPF_HELO_NONE, SPF_PASS autolearn=no autolearn_force=no version=3.4.0 Received: from mail.kernel.org (mail.kernel.org [198.145.29.99]) by smtp.lore.kernel.org (Postfix) with ESMTP id 200C8C433E0 for ; Wed, 8 Jul 2020 07:40:24 +0000 (UTC) Received: from vger.kernel.org (vger.kernel.org [23.128.96.18]) by mail.kernel.org (Postfix) with ESMTP id E7FF920720 for ; Wed, 8 Jul 2020 07:40:23 +0000 (UTC) Authentication-Results: mail.kernel.org; dkim=pass (2048-bit key) header.d=linutronix.de header.i=@linutronix.de header.b="WhewwSnE"; dkim=permerror (0-bit key) header.d=linutronix.de header.i=@linutronix.de header.b="UXxEHP+l" Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1726479AbgGHHkW (ORCPT ); Wed, 8 Jul 2020 03:40:22 -0400 Received: from Galois.linutronix.de ([193.142.43.55]:46380 "EHLO galois.linutronix.de" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1726325AbgGHHkW (ORCPT ); Wed, 8 Jul 2020 03:40:22 -0400 From: Kurt Kanzenbach DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=linutronix.de; s=2020; t=1594194019; 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=deFGfHxYZYgFx9JerGX/g9w6hxTKxOGElkA7QsAXZ3w=; b=WhewwSnEfGMkGBbezfukKi28AdipCum2wKduadjzvIOk+jrBL5e8y8T/hYFJrBJ+6crdbZ hZhqae76KBRhQWKvIxiM8/+G45D4bahl9w/EYMDqDpkVQ2n+vxEDXK2UJXFa1omIr6NdPu GZKDdu4SipOERb1v/l0216WfWacWodvOFRRtEAU0kEExQuAa1Ix5fRIfNqbBLiqKWeiuT2 Jz+EPJuMsU135R+GllJirrGDxQe+WncXbgf9TA4e3/mK2mIV/GalUazXC4deue7wiiRtbB jDsYrPgLMilJ7eBOR2s747Hf8EUipgTePQQFaP6K8r556E+W+a+WnWpsW6zfCQ== DKIM-Signature: v=1; a=ed25519-sha256; c=relaxed/relaxed; d=linutronix.de; s=2020e; t=1594194019; 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=deFGfHxYZYgFx9JerGX/g9w6hxTKxOGElkA7QsAXZ3w=; b=UXxEHP+lGDBaQFgs7Dq8HysuTS86gLQtlL8hTV3eNdK6Lhb0uGEaSsAfsiAqRrmv0JfK+L 1c6panhvNY28iIAA== To: Sergey Senozhatsky Cc: Andy Shevchenko , Sergey Senozhatsky , Tony Lindgren , Petr Mladek , Raul Rangel , Sergey Senozhatsky , linux-kernel , Greg Kroah-Hartman , Andy Shevchenko , "S\, Shirish" , Peter Zijlstra , John Ogness , Steven Rostedt Subject: Re: UART/TTY console deadlock In-Reply-To: <20200706144314.GB1485@jagdpanzerIV.localdomain> References: <20200630102141.GA11587@alley> <20200630105512.GA530@jagdpanzerIV.localdomain> <20200630122239.GD6173@alley> <20200630130534.GB145027@jagdpanzerIV.localdomain> <20200630180255.GD37466@atomide.com> <20200702051213.GB3450@jagdpanzerIV.localdomain> <20200702160514.GK37466@atomide.com> <20200703103241.GB182102@jagdpanzerIV.localdomain> <877dvg6ft6.fsf@kurt> <20200706144314.GB1485@jagdpanzerIV.localdomain> Date: Wed, 08 Jul 2020 09:40:17 +0200 Message-ID: <87o8oqa1zy.fsf@kurt> MIME-Version: 1.0 Content-Type: multipart/signed; boundary="=-=-="; micalg=pgp-sha512; protocol="application/pgp-signature" Sender: linux-kernel-owner@vger.kernel.org Precedence: bulk List-ID: X-Mailing-List: linux-kernel@vger.kernel.org --=-=-= Content-Type: text/plain Content-Transfer-Encoding: quoted-printable On Mon Jul 06 2020, Sergey Senozhatsky wrote: > On (20/07/06 13:31), Kurt Kanzenbach wrote: >> >> @@ -2275,6 +2275,7 @@ int serial8250_do_startup(struct uart_port *por= t) >> >> >> >> if (port->irq && !(up->port.flags & UPF_NO_THRE_TEST)) { >> >> unsigned char iir1; >> >> + >> >> /* >> >> * Test for UARTs that do not reassert THRE when the >> >> * transmitter is idle and the interrupt has already >> >> @@ -2284,8 +2285,6 @@ int serial8250_do_startup(struct uart_port *por= t) >> >> * allow register changes to become visible. >> >> */ >> >> spin_lock_irqsave(&port->lock, flags); >> >> - if (up->port.irqflags & IRQF_SHARED) >> >> - disable_irq_nosync(port->irq); >> >> >> >> wait_for_xmitr(up, UART_LSR_THRE); >> >> serial_port_out_sync(port, UART_IER, UART_IER_THRI); >> >> @@ -2297,8 +2296,6 @@ int serial8250_do_startup(struct uart_port *por= t) >> >> iir =3D serial_port_in(port, UART_IIR); >> >> serial_port_out(port, UART_IER, 0); >> >> >> >> - if (port->irqflags & IRQF_SHARED) >> >> - enable_irq(port->irq); >> >> spin_unlock_irqrestore(&port->lock, flags); >> >> >> >> /* >> > >> > ...which effectively is a revert of >> > >> > 768aec0b5bcc ("serial: 8250: fix shared interrupts issues with SMP and >> > RT kernels") >>=20 >> Please, don't revert that commit. I've faced the same issue as described >> in the commit log. There is hardware available with shared UART >> interrupt lines. > > Will this patch break that hardware? > https://lore.kernel.org/lkml/20200702051213.GB3450@jagdpanzerIV.localdoma= in/ I'm not sure how this patch will help with the situation. Because at the point of that THRE test the irq handler isn't registered. It's registered a few lines below (up->ops->setup_irq()) meaning the irq line has to be disabled if shared. Otherwise the kernel might detect a spurious irq and disables it. That's at least my understanding of the problem (see commit message from 54e53b2e8081 ("tty: serial: 8250: pass IRQ shared flag to UART ports")). Thanks, Kurt --=-=-= Content-Type: application/pgp-signature; name="signature.asc" -----BEGIN PGP SIGNATURE----- iQIzBAEBCgAdFiEEooWgvezyxHPhdEojeSpbgcuY8KYFAl8FeGEACgkQeSpbgcuY 8KZFuw//cx3Oy+/kFOtj/m/GQiBhw+JVAJ4ixZ92RmC564AEcTZoGGwpqXE7an70 FIUvBNKAzmk6w5LR628Mx29Qee4e35n6YMgPcAjbaCwwDiMq5In5tpnkowPEvNwi IY5J3dnaLR+MkQxg3NjYu5LBDArW0MugDqOnj1RefUIToqQCQgMb4wEskUlaDvFC e7gv9NeOTXMg4etj5MFnWiTRTcdCCBV1HjzZ9NRFeLCm/mKm2Q/KR1MIkZxmM22/ dGzhrD15Ly7hDyXYoPJY9g4P2+pJsY3kqrZb5FsVrYhjR5ZlGB8DOIVHwJ/f98YV bolld/ntOqWlzEeOwrmjYbSgVcW56lBMA+5HV4pOUbq6EcXyEAzWcVa4FaYsZdvJ iRxMuC3JjRRve3mBOrITv2egPCktZeSeZExpAXzyuYbQpNwurvVQjjVL+RPJrkpx 2RnAikQtz5E2EcyxbZmNcS687sweUFRsGhlT/zE7dJ+cOd+pfM0kvrJSnNbdxNC5 /w//o5y75M5pV2CbNhvfpgB6I/aik/SxATHG6NMF3IojM/SO/gb7lmdFWpYLwP6f k45gcwC9FZoTNHmyYzlitbs45kMfgqPQAnKAqYnRJAfl/CgOCnJZhO5DvjiX671K 32NlT5V0x/5bPcnkkgn1tYK1x68ivgeXDSjj244lns5a7KknF5A= =lDDH -----END PGP SIGNATURE----- --=-=-=--