From mboxrd@z Thu Jan 1 00:00:00 1970 From: mark.rutland@arm.com (Mark Rutland) Date: Mon, 14 Jan 2013 15:36:12 +0000 Subject: [PATCHv2 1/4] clockevents: Add generic timer broadcast receiver In-Reply-To: References: <1357742770-15028-1-git-send-email-mark.rutland@arm.com> <1357742770-15028-2-git-send-email-mark.rutland@arm.com> <20130114112951.GC7990@e106331-lin.cambridge.arm.com> <20130114121247.GD7990@e106331-lin.cambridge.arm.com> Message-ID: <20130114153612.GF7990@e106331-lin.cambridge.arm.com> To: linux-arm-kernel@lists.infradead.org List-Id: linux-arm-kernel.lists.infradead.org On Mon, Jan 14, 2013 at 02:17:26PM +0000, Thomas Gleixner wrote: > On Mon, 14 Jan 2013, Mark Rutland wrote: > > On Mon, Jan 14, 2013 at 11:50:55AM +0000, Thomas Gleixner wrote: > > > On Mon, 14 Jan 2013, Mark Rutland wrote: > > > > > > > On Mon, Jan 14, 2013 at 11:06:31AM +0000, Thomas Gleixner wrote: > > > > > On Wed, 9 Jan 2013, Mark Rutland wrote: > > > > > > +#ifdef CONFIG_GENERIC_CLOCKEVENTS_BROADCAST > > > > > > +extern int tick_receive_broadcast(void); > > > > > > +#else > > > > > > +static inline int tick_receive_broadcast(void) > > > > > > +{ > > > > > > + return 0; > > > > > > +} > > > > > > > > > > What's the inline function for? If an arch does not have broadcasting > > > > > support it should not have a receive broadcast function call either. > > > > > > > > That was how this was originally structured [1], but Santosh suggested this > > > > would break the build for !GENERIC_CLOCKEVENTS_BROADCAST [1]. It means that the > > > > arch-specific receive path (i.e. IPI handler) doesn't have to be #ifdef'd, > > > > which makes it less ugly. > > > > > > Hmm. If you want to keep the IPI around unconditionally the inline > > > makes some sense, though the question is whether keeping an unused IPI > > > around makes sense in the first place. I'd rather see a warning that > > > an unexpected IPI happened than a silent inline function being called. > > > > How about I add a warning (e.g. "Impossible timer broadcast received.") and > > return -EOPNOTSUPP when !GENERIC_CLOCKEVENTS_BROADCAST? > > You still need to do something with the return value in the arch IPI > code, right? Good point. Having the stub when !CONFIG_GENERIC_CLOCKEVENTS_BROADCAST is clearly problematic. I'll go with your original suggestion, removing the tick_receive_broadcast stub for !CONFIG_GENERIC_CLOCKEVENTS_BROADCAST and I'll #idef the IPI_TIMER handler. That way it'll fall down to the standard warning for an unexpected/unknown IPI for arch/arm at least. > > > > > Is anything going to use the return value? > > > > > > > > I'd added this after looking at the x86 lapic timers, where interrupts might > > > > remain pending over a kexec, and lapic interrupts come up before timers are > > > > registered. The return value is useful for shutting down the timer in that case > > > > (see x86's local_apic_timer_interrupt). > > > > > > Right, though then you need to check for evt->event_handler as well. > > > > I thought this previously also [1], but I couldn't find any path such that a > > tick_cpu_device would have an evtdev without an event_handler. We always set the > > handler before setting evtdev, and alway wipe evtdev before wiping the handler. > > > > Have I missed something? > > That's an x86 specific issue. Though we could try and make that > functionality completely generic. Just to check: is the evt->event_handler check necessary? > Thanks, > > tglx > Thanks, Mark.