From mboxrd@z Thu Jan 1 00:00:00 1970 From: compudj@krystal.dyndns.org (Mathieu Desnoyers) Date: Tue, 16 Feb 2010 12:05:40 -0500 Subject: [ltt-dev] LTTng0.158 Linux-2629-RT kernel BUG: sleeping function called from invalid context at kernel/rtmutex.c:685 In-Reply-To: References: <1266337450.24271.140.camel@gandalf.stny.rr.com> <20100216164744.GA25115@Krystal> Message-ID: <20100216170540.GA28039@Krystal> * 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. > > > > 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. Thanks, Mathieu > > Thanks, > > tglx > -- Mathieu Desnoyers OpenPGP key fingerprint: 8CD5 52C3 8E3C 4140 715F BA06 3F25 A8FE 3BAE 9A68