From mboxrd@z Thu Jan 1 00:00:00 1970 From: Peter Hurley Subject: Re: [PATCH] Fix data loss in cdc-acm Date: Wed, 05 Aug 2015 13:36:35 -0400 Message-ID: <55C249A3.6030809@hurleysoftware.com> References: <55AC1883.4050605@svenbrauch.de> <20150720172546.GF20628@localhost> <55AD38E5.1090807@svenbrauch.de> <1437486195.3823.13.camel@suse.com> <55AEBD06.6020402@svenbrauch.de> <55AED708.903@hurleysoftware.com> <55AEE805.9050204@svenbrauch.de> <55B01554.90201@hurleysoftware.com> <55B01EDE.3050503@svenbrauch.de> Mime-Version: 1.0 Content-Type: text/plain; charset=utf-8 Content-Transfer-Encoding: 7bit Return-path: In-Reply-To: <55B01EDE.3050503-ITmcY+a7/CDoK6nBLMlh1Q@public.gmane.org> Sender: linux-usb-owner-u79uwXL29TY76Z2rM5mHXA@public.gmane.org To: Sven Brauch Cc: Oliver Neukum , Johan Hovold , Linux Kernel Mailing List , One Thousand Gnomes , Toby Gray , linux-usb-u79uwXL29TY76Z2rM5mHXA@public.gmane.org, linux-serial-u79uwXL29TY76Z2rM5mHXA@public.gmane.org List-Id: linux-serial@vger.kernel.org On 07/22/2015 06:53 PM, Sven Brauch wrote: > Hi, > > On 23/07/15 00:12, Peter Hurley wrote: >> The premature unthrottle actually leads to the data loss but the throttling >> with a mere 2K left is _way too late_. > Ok, yes, I think so too. > >> 10ms is a _really_ long time for a cpu not to attend to a kworker. I haven't forgotten about this problem and I still plan to look into why the long delay, particularly focusing on the scheduling latency from tty_flip_buffer_push() => flush_to_ldisc(). Regards, Peter Hurley >> Which raises 2 questions: >> 1. What are the termios settings of the tty receiving input? Is it 'raw' >> mode or typical terminal mode (icanon, echo, etc.) or something else? > In my test code, I open the tty like > fd = open("/dev/ttyACM0", O_RDWR | O_NOCTTY | O_NONBLOCK); > I don't make any other changes to the default settings. To be honest, > I'm not sure in which mode it is operating then (I was assuming raw, but > I might be wrong?). > >> 2. Are there RT threads that are hogging cpu time? > I can't see any, I think the only thing which occasionally goes to RT is > pulseaudio (but during at least some of the tests I wasn't even playing > audio, so that sounds very unplausible to me). I also cannot see a > correlation between failure rate and CPU load. > > Best regards, > Sven > -- To unsubscribe from this list: send the line "unsubscribe linux-usb" in the body of a message to majordomo-u79uwXL29TY76Z2rM5mHXA@public.gmane.org More majordomo info at http://vger.kernel.org/majordomo-info.html