From mboxrd@z Thu Jan 1 00:00:00 1970 From: naresh.kernel@gmail.com (naresh kamboju) Date: Wed, 17 Feb 2010 16:06:28 +0530 Subject: [ltt-dev] LTTng0.158 Linux-2629-RT kernel BUG: sleeping function called from invalid context at kernel/rtmutex.c:685 In-Reply-To: <20100216170540.GA28039@Krystal> References: <1266337450.24271.140.camel@gandalf.stny.rr.com> <20100216164744.GA25115@Krystal> <20100216170540.GA28039@Krystal> Message-ID: Hi, On Tue, Feb 16, 2010 at 10:35 PM, Mathieu Desnoyers wrote: > * Thomas Gleixner (tglx at 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(): >> > >> > ?* Synchronization rules: Callers must prevent restarting of the timer, >> > ?* otherwise this function is meaningless. It must not be called from >> > ?* interrupt contexts. The caller must not hold locks which would prevent >> > ?* completion of the timer's handler. The timer's handler must not call >> > ?* add_timer_on(). Upon exit the timer is not queued and the handler is >> > ?* not running on any CPU. >> >> Errm. The documentation says: >> >> ? ? ? "The timer's handler must not call add_timer_on()." >> >> It's not talking about a timer which was initialized with >> add_timer_on(). >> >> ?And 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, >> >> ? ? ? tglx >> > > -- > Mathieu Desnoyers > OpenPGP key fingerprint: 8CD5 52C3 8E3C 4140 715F ?BA06 3F25 A8FE 3BAE 9A68