fix heartbeat

The heartbeat function will not execute properly on Gemini without this patch. (Check for cpu 0 removed from gemini_heartbeat.)

-VAL

diff -Nru a/arch/ppc/kernel/time.c b/arch/ppc/kernel/time.c
@@ -208,7 +208,8 @@
 	smp_local_timer_interrupt(regs);
 #endif /* CONFIG_SMP */
 
-	if (ppc_md.heartbeat && !ppc_md.heartbeat_count--)
+	if (ppc_md.heartbeat && !smp_processor_id() &&
+	    !ppc_md.heartbeat_count--)
 		ppc_md.heartbeat();
 
 	hardirq_exit(cpu);

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CHRP needs the heartbeat function called on all cpus, IIRC.

Clearly the heartbeat_count needs to be per-cpu or else pushed into the heartbeat function. How about we make it just

	if (ppc_md.heartbeat)
		ppc_md.heartbeat();

and let the heartbeat function do the if (!smp_processor_id()) and the if (!heartbeat_count--) if it wants?

Paul.

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Ah, I see, the heartbeat_count is now being decremented once per timer interrupt, instead of smp_nr_cpus times per timer interrupt. Last time I checked, it was still possible for the heartbeat count to go negative.

It's fine the way it is. Sorry for the unnecessary patch.

-VAL

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Tsk, shouldn't read patches on the weekend... Here's the current code:

        if (ppc_md.heartbeat && !ppc_md.heartbeat_count--)
                ppc_md.heartbeat();

This decrements the count on every processor. If cpu 0 turns off interrupts interrupts for a while, we get two effects: heartbeat_count is now decremented smp_nr_cpus - 1 times per timer interrupt, and if your heartbeat function doesn't explicitly prevent it, your heartbeat count could go negative.

An alternative that allows you to run the heartbeat function on whatever cpus you like but decrements the heartbeat once per timer interrupt is:

        if (ppc_md.heartbeat && !smp_processor_id()
	         ppc_md.heartbeat_count--)

        if (!ppc_md.heartbeat_count)
                ppc_md.heartbeat();

Howz that?

-VAL

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