From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S932236AbVHRPOF (ORCPT ); Thu, 18 Aug 2005 11:14:05 -0400 Received: (majordomo@vger.kernel.org) by vger.kernel.org id S932241AbVHRPOF (ORCPT ); Thu, 18 Aug 2005 11:14:05 -0400 Received: from ylpvm29-ext.prodigy.net ([207.115.57.60]:5564 "EHLO ylpvm29.prodigy.net") by vger.kernel.org with ESMTP id S932236AbVHRPOE (ORCPT ); Thu, 18 Aug 2005 11:14:04 -0400 X-ORBL: [64.108.208.122] In-Reply-To: <21FFE0795C0F654FAD783094A9AE1DFC0830FE03@cof110avexu4.global.avaya.com> References: <21FFE0795C0F654FAD783094A9AE1DFC0830FE03@cof110avexu4.global.avaya.com> Mime-Version: 1.0 (Apple Message framework v622) Content-Type: text/plain; charset=US-ASCII; format=flowed Message-Id: <39eeb491a777cbc24b6406595b21fb15@mindspring.com> Content-Transfer-Encoding: 7bit Cc: , "Mike Galbraith" From: Hal Wigoda Subject: Re: Debugging kernel semaphore contention and priority inversion Date: Thu, 18 Aug 2005 10:13:50 -0500 To: "Davda, Bhavesh P \(Bhavesh\)" X-Mailer: Apple Mail (2.622) Sender: linux-kernel-owner@vger.kernel.org X-Mailing-List: linux-kernel@vger.kernel.org will netconsole install on mandriva? On Aug 18, 2005, at 9:50 AM, Davda, Bhavesh P ((Bhavesh)) wrote: >> -----Original Message----- >> From: Mike Galbraith [mailto:efault@gmx.de] >> Sent: Wednesday, August 17, 2005 11:10 PM >> At 09:43 PM 8/17/2005 -0600, you wrote: >>>> >>>> Have you tried sysrq t? See the Documentation/sysrq.txt file. >>> >>> This is a headless system. >> >> You could try netconsole. > > Haven't heard of it before. Will look into it. But I doubt it will help > pinpoint the semaphore holder, if all I can do is sysrq stuff. > >> >>>> >>>> How stuck is the system? >>>> >>>> Keith >>> >>> Very. Only pingable, but can't login via >> telnet/ssh/anything. Reason is >>> the same reason the low priority mystery task is unable to run and >>> release the held semaphore. >> >> (hmm. I'm obviously missing some original context here) >> >> Sounds like there must be another player who is RT prio + spinning. >> >> -Mike > > Very good! Yes, I left out that piece of detail in my original posting. > There is a real low priority (4) SCHED_FIFO (hence still higher than > any > SCHED_OTHER) task spinning. But it is not the semaphore holder. I am > trying to identify which kernel thread (because that's most likely) > running at SCHED_OTHER real low priority (too nice) is holding the > semaphore, locking out a priority 50 SCHED_FIFO task in its sys_write() > as a result. > > Thanks > > - Bhavesh > > Bhavesh P. Davda | Distinguished Member of Technical Staff | Avaya | > 1300 West 120th Avenue | B3-B03 | Westminster, CO 80234 | U.S.A. | > Voice/Fax: 303.538.4438 | bhavesh@avaya.com > - > To unsubscribe from this list: send the line "unsubscribe > linux-kernel" in > the body of a message to majordomo@vger.kernel.org > More majordomo info at http://vger.kernel.org/majordomo-info.html > Please read the FAQ at http://www.tux.org/lkml/ >