From mboxrd@z Thu Jan 1 00:00:00 1970 From: naresh kamboju Subject: Re: LTTng0.158 Linux-2629-RT kernel BUG: sleeping function called from invalid context at kernel/rtmutex.c:685 Date: Wed, 17 Feb 2010 16:06:28 +0530 Message-ID: References: <1266337450.24271.140.camel@gandalf.stny.rr.com> <20100216164744.GA25115@Krystal> <20100216170540.GA28039@Krystal> Mime-Version: 1.0 Content-Type: text/plain; charset="iso-8859-1" Content-Transfer-Encoding: quoted-printable Cc: linux-rt-users@vger.kernel.org, linux-kernel@vger.kernel.org, Steven Rostedt , ltt-dev@lists.casi.polymtl.ca, Thomas Gleixner , Ingo Molnar To: Mathieu Desnoyers Return-path: In-Reply-To: <20100216170540.GA28039@Krystal> List-Unsubscribe: , List-Archive: List-Post: List-Help: List-Subscribe: , Errors-To: ltt-dev-bounces@lists.casi.polymtl.ca List-Id: linux-rt-users.vger.kernel.org Hi, On Tue, Feb 16, 2010 at 10:35 PM, Mathieu Desnoyers wrote: > * Thomas Gleixner (tglx@linutronix.de) wrote: >> On Tue, 16 Feb 2010, Mathieu Desnoyers wrote: >> > > The function is called from an IPI. That's a LTTNG problem, not a RT= one. yes. it's seems be a LTTng0.158 problem. I have tested with below combinations. 2.6.29 ->no issues 2.6.29+LTTng0.100 ->no issues 2.6.29+LTTng0.158 ->no issues 2.6.29-RT ->no issues 2.6.29-RT+LTTng0.100 ->no issues 2.6.29-RT+LTTng0.158 ->BUG reported. >> > >> > I use del_timer in IPI to delete lttng per-cpu timers on all CPUs. I >> > have to do this because timers created with add_timer_on are documented >> > to be incompatible with del_timer_sync(): >> > >> > =A0* Synchronization rules: Callers must prevent restarting of the tim= er, >> > =A0* otherwise this function is meaningless. It must not be called from >> > =A0* interrupt contexts. The caller must not hold locks which would pr= event >> > =A0* completion of the timer's handler. The timer's handler must not c= all >> > =A0* add_timer_on(). Upon exit the timer is not queued and the handler= is >> > =A0* not running on any CPU. >> >> Errm. The documentation says: >> >> =A0 =A0 =A0 "The timer's handler must not call add_timer_on()." >> >> It's not talking about a timer which was initialized with >> add_timer_on(). >> >> =A0And your per cpu timer handlers have no requirement to call >> add_timer_on() simply because add/mod_timer() is requeueing the timer >> on the same cpu on which the handler runs. >> >> So the IPI is just a solution for a non existing problem. > > Oh, right. Thanks for the explanation. I'll look into moving LTTng to a > saner del_timer_sync() scheme to delete the timers. Could you give more info regarding, what kind of changes we can work on. let me also work around on it. Best regards, Naresh Kamboju > > Thanks, > > Mathieu > >> >> Thanks, >> >> =A0 =A0 =A0 tglx >> > > -- > Mathieu Desnoyers > OpenPGP key fingerprint: 8CD5 52C3 8E3C 4140 715F =A0BA06 3F25 A8FE 3BAE = 9A68