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Open Source and information security mailing list archives
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Date: Wed, 21 Mar 2012 17:50:34 -0400 From: chetan loke <loke.chetan@...il.com> To: "Keller, Jacob E" <jacob.e.keller@...el.com> Cc: Richard Cochran <richardcochran@...il.com>, "netdev@...r.kernel.org" <netdev@...r.kernel.org>, "e1000-devel@...ts.sourceforge.net" <e1000-devel@...ts.sourceforge.net>, "Kirsher, Jeffrey T" <jeffrey.t.kirsher@...el.com>, "Ronciak, John" <john.ronciak@...el.com>, "john.stultz@...aro.org" <john.stultz@...aro.org>, "tglx@...utronix.de" <tglx@...utronix.de> Subject: Re: [PATCH net V4 2/2] igb: offer a PTP Hardware Clock instead of the timecompare method On Wed, Mar 21, 2012 at 1:09 PM, Keller, Jacob E <jacob.e.keller@...el.com> wrote: >> -----Original Message----- >> From: Richard Cochran [mailto:richardcochran@...il.com] >> Sent: Wednesday, March 21, 2012 10:00 AM >> To: chetan loke >> Cc: netdev@...r.kernel.org; e1000-devel@...ts.sourceforge.net; Keller, Jacob >> E; Kirsher, Jeffrey T; Ronciak, John; john.stultz@...aro.org; >> tglx@...utronix.de >> Subject: Re: [PATCH net V4 2/2] igb: offer a PTP Hardware Clock instead of the >> timecompare method >> >> Can you please explain how using a seqlock could help here? >> >> Thanks, >> Richard > > My understanding of the seqlock, is that it prevents starvation of the hwtstamp calls in the rx and tx routines if/when a user hammers the gettime ioctl due to bad software design where 100+ apps are wanting direct access to the PHC. > Richard - Intent is to make the readers(get_time) wait (or return last read value if the seq_counter tripped because you know that this value was recent) and let the tx/rx path continue. I haven't looked in more details but as Jake mentioned you will also need to change the way you read the values(by not using timecounter_read in get_time). thanks Chetan -- To unsubscribe from this list: send the line "unsubscribe netdev" in the body of a message to majordomo@...r.kernel.org More majordomo info at http://vger.kernel.org/majordomo-info.html
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