Hi, On Tue, Feb 16, 2010 at 10:35 PM, Mathieu Desnoyers <compudj@xxxxxxxxxxxxxxxxxx> wrote: > * Thomas Gleixner (tglx@xxxxxxxxxxxxx) 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 -- To unsubscribe from this list: send the line "unsubscribe linux-rt-users" in the body of a message to majordomo@xxxxxxxxxxxxxxx More majordomo info at http://vger.kernel.org/majordomo-info.html
