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=-3.7 required=3.0 tests=BAYES_00, HEADER_FROM_DIFFERENT_DOMAINS,MAILING_LIST_MULTI,SPF_HELO_NONE,SPF_PASS, URIBL_BLOCKED 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 E252CC433DB for ; Wed, 24 Feb 2021 11:36:36 +0000 (UTC) Received: from vger.kernel.org (vger.kernel.org [23.128.96.18]) by mail.kernel.org (Postfix) with ESMTP id 96DFF60C3E for ; Wed, 24 Feb 2021 11:36:36 +0000 (UTC) Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S234425AbhBXLgb (ORCPT ); Wed, 24 Feb 2021 06:36:31 -0500 Received: from mail-oi1-f177.google.com ([209.85.167.177]:34401 "EHLO mail-oi1-f177.google.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S232545AbhBXLga (ORCPT ); Wed, 24 Feb 2021 06:36:30 -0500 Received: by mail-oi1-f177.google.com with SMTP id w69so2098290oif.1; Wed, 24 Feb 2021 03:36:14 -0800 (PST) X-Google-DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=1e100.net; s=20161025; h=x-gm-message-state:mime-version:references:in-reply-to:from:date :message-id:subject:to:cc; bh=V7g4KDGkN4bTV6Y86WxSYXBrPiMRP6Icmxr97tcDgIM=; b=EgwRhjOgHFg0j72uBBfZLyOPW4R5XP0jRtrVGgnp0EJ/HlQ8CtKX4It7JnEolzAluH HiQ6td+kZGT3zCw6bXHf0cCbUjYjSgn7+7MkMNCyrLTwgkQpYGHalQv+PeYDEcCdvbkr EXkQ4UWpDRy+wvbaGiGKYwOfjJOby2mAKjl8ODFrJ56WV3DB3IAWTglykEGCrndpOo6i ugylpOA0tas4ADjGAI2Mi25IIP0zBYccdkGwWjNmiucGEc4Mw51vAxgOUnjt5L5UiqAr SDuhAQgEwCT5IOqu0TLp3qAdk7nRV1rvw/1BfG5XPsSdaRo973Dw0HegvuqQlsykKc3q PSzA== X-Gm-Message-State: AOAM531y2sniSo+SfFfPGHum01iO7l85ZDlr6PLBwecdmAl0Y0xgqKTm YXPvFg2NheWNktJY1M3vuViEiJqadF6n9UZfaOHRo7gPrlY= X-Google-Smtp-Source: ABdhPJyyC3OgPRc8t7eL+A4bFMUBKjhhxC28ihqPvnbBLD0NPyTb8VvBUkXvZsvXDHxGs0xnf2E2wchLYsmgbSu4vZ0= X-Received: by 2002:aca:d8c6:: with SMTP id p189mr2430015oig.54.1614166549412; Wed, 24 Feb 2021 03:35:49 -0800 (PST) MIME-Version: 1.0 References: <20210220230248.320870-1-ztong0001@gmail.com> In-Reply-To: From: Geert Uytterhoeven Date: Wed, 24 Feb 2021 12:35:37 +0100 Message-ID: Subject: Re: [PATCH] video: fbdev: pm2fb: avoid stall on fb_sync To: Tong Zhang Cc: Randy Dunlap , "Gustavo A. R. Silva" , Sam Ravnborg , Bartlomiej Zolnierkiewicz , DRI Development , Linux Fbdev development list , open list Content-Type: text/plain; charset="UTF-8" Precedence: bulk List-ID: X-Mailing-List: linux-fbdev@vger.kernel.org Hi Tong, On Sun, Feb 21, 2021 at 1:05 AM Tong Zhang wrote: > On Sat, Feb 20, 2021 at 6:33 PM Randy Dunlap wrote: > > On 2/20/21 3:02 PM, Tong Zhang wrote: > > > pm2fb_sync is called when doing /dev/fb read or write. > > > The original pm2fb_sync wait indefinitely on hardware flags which can > > > possibly stall kernel and make everything unresponsive. > > > Instead of waiting indefinitely, we can timeout to give user a chance to > > > get back control. > > > > Is this a real problem or theoretical? > > Does someone still use this driver? > > I currently have this problem on my machine. > I have submitted a revised patch -- which includes the console log. Your machine is "QEMU Standard"? Can this happen on real hardware, too, or is this a deficiency in QEMU, which should be fixed there? Gr{oetje,eeting}s, Geert -- Geert Uytterhoeven -- There's lots of Linux beyond ia32 -- geert@linux-m68k.org In personal conversations with technical people, I call myself a hacker. But when I'm talking to journalists I just say "programmer" or something like that. -- Linus Torvalds