On Tue, Sep 04, 2012 at 03:33:50PM -0700, Paul E. McKenney wrote: > On Fri, Aug 31, 2012 at 11:00:52AM -0700, Josh Triplett wrote: > > On Thu, Aug 30, 2012 at 11:56:17AM -0700, Paul E. McKenney wrote: > > > From: "Paul E. McKenney" <paul.mcken...@linaro.org> > > > > > > There is a need to use RCU from interrupt context, but either before > > > rcu_irq_enter() is called or after rcu_irq_exit() is called. If the > > > interrupt occurs from idle, then lockdep-RCU will complain about such > > > uses, as they appear to be illegal uses of RCU from the idle loop. > > > In other environments, RCU_NONIDLE() could be used to properly protect > > > the use of RCU, but RCU_NONIDLE() currently cannot be invoked except > > > from process context. > > > > > > This commit therefore modifies RCU_NONIDLE() to permit its use more > > > globally. > > > > > > Reported-by: Steven Rostedt <rost...@goodmis.org> > > > Signed-off-by: Paul E. McKenney <paul.mcken...@linaro.org> > > > Signed-off-by: Paul E. McKenney <paul...@linux.vnet.ibm.com> > > > > Something seems wrong about this. The addition of EXPORT_SYMBOL_GPL > > suggests that such interrupt handlers might live in modules. In what > > situation might a module interrupt handler get called from the idle > > loop, before rcu_irq_enter or after rcu_irq_exit, and need to know that > > when using RCU? > > Drivers can be in modules, in which case their interrupt handlers will > also be in the corresponding module. I do agree that in most cases, > the irq_enter() and irq_exit() hooks would be invoked by non-module code, > but I do believe that I had to add those exports due to build failures.
I definitely understand that drivers can have interrupt handlers in modules; however, I have a hard time seeing a case where a module has a legitimate reason to invoke rcu_irq_enter or rcu_irq_exit, or to run before the former or after the latter. - Josh Triplett -- To unsubscribe from this list: send the line "unsubscribe linux-kernel" in the body of a message to majord...@vger.kernel.org More majordomo info at http://vger.kernel.org/majordomo-info.html Please read the FAQ at http://www.tux.org/lkml/
