From mboxrd@z Thu Jan 1 00:00:00 1970 From: tglx@linutronix.de (Thomas Gleixner) Date: Tue, 16 Feb 2010 18:01:49 +0100 (CET) Subject: [ltt-dev] LTTng0.158 Linux-2629-RT kernel BUG: sleeping function called from invalid context at kernel/rtmutex.c:685 In-Reply-To: <20100216164744.GA25115@Krystal> References: <1266337450.24271.140.camel@gandalf.stny.rr.com> <20100216164744.GA25115@Krystal> Message-ID: 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. Thanks, tglx