On Fri, Aug 27, 2010 at 2:01 AM, Thomas Gleixner <tglx@xxxxxxxxxxxxx> wrote: > On Fri, 20 Aug 2010, Jeremy Brown wrote: > >> We're using kernel 2.6.33.5 with corresponding 2.6.33.5-rt25 patches. >> __setup_irq in request_kernel/irq/manage.c contains a block guarded by >> a raw spinlock, with a preceding comment noting "The following block >> of code has to be executed atomically". Why is this so? > > Because this lock protects against an incoming interrupt. > >> I ask because during RTC setup, this atomic region is causing calls to >> twl4030_sih_* functions to fail on my BeagleBoard platform (see stack >> trace below from a previous thread.). As Gowrishankar noted in the >> previous thread, those routines use (non-raw) spinlocking. As Thomas >> noted, they also call queue_work, which in turn relies on non-raw >> spinlocking, so just patching up the twl4030_sih_* functions to use >> raw calls doesn't solve the problem. I'm presently experimenting >> with: >> >> a) pulling the calls to__irq_set_trigger and desc->chip->startup to a >> spot after the call to raw_spin_unlock_irqrestore, or >> >> b) making the atomic region use non-raw locking. > > Neither of those approaches will work. > >> However, I'm not really sure what the consequences of other approach >> are likely to be. I'd be grateful for any thoughts and/or guidance >> that will keep me from wasting time and/or breaking things in subtle >> and confusing ways. > > The right thing to do is to convert the driver to the chip_bus_lock() > functionality. Thanks for this, and for the driver references below. I recently stumbled chip_bus_lock, but hadn't yet tried using it. For the short term, we've abandoned the RTC entirely, but if we return to it, I'll take a stab at a chip_bus_lock conversion. Thanks again, Jeremy > See drivers/mfd/88pm860x-core.c > drivers/mfd/ab8500-core.c > drivers/mfd/max8925-core.c > drivers/mfd/stmpe.c > drivers/mfd/wm831x-irq.c > drivers/mfd/wm8350-irq.c > drivers/mfd/wm8994-irq.c > > for examples. That'd be a nice cleanup for that driver anyway. See > also commit 70aedd24d20e75198f5a0b11750faabbb56924e for documentation > about the core infrastructure. > > Thanks, > > tglx > -- 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
