On Fri, 2009-11-06 at 09:10 +0100, Richard Cochran wrote:
> On Wed, Nov 04, 2009 at 11:16:21PM +0100, Philippe Gerum wrote:
> > Core 0 waits for core 1 to acknowledge the critical IPI, but that
> > lazybones prefers to sleep. Likely because it did not receive the IPI in
> > question, actually (it should raise a bit in __ipipe_cpu_sync_map, see
> > __ipipe_do_critical_sync). You may want to find the reason why the IPI
> > sent in ipipe_critical_enter() does not propagate to the other core.
>
> In file arch/powerpc/kernel/smp.c line 160, it appears that the IPIPE
> ifdef code is not reached when msg==3, which is the important value,
> AFAIKT.
>
> I have neither CONFIG_DEBUGGER nor CONFIG_KEXEC defined.
>
>
> int smp_request_message_ipi(int virq, int msg)
> {
> int err;
>
> if (msg < 0 || msg > PPC_MSG_DEBUGGER_BREAK) {
> return -EINVAL;
> }
> #if !defined(CONFIG_DEBUGGER) && !defined(CONFIG_KEXEC)
> if (msg == PPC_MSG_DEBUGGER_BREAK) {
> return 1;
> }
> #endif
> #ifdef CONFIG_IPIPE
> if (msg == PPC_MSG_DEBUGGER_BREAK)
> /* Piggyback the debugger IPI for the I-pipe. */
> __ipipe_register_ipi(virq);
> #endif
>
> err = request_irq(virq, smp_ipi_action[msg], IRQF_DISABLED|IRQF_PERCPU,
> smp_ipi_name[msg], 0);
> WARN(err < 0, "unable to request_irq %d for %s (rc %d)\n",
> virq, smp_ipi_name[msg], err);
>
> return err;
> }
Ouch. I just can't believe this went unnoticed for that long... Well, no
wonder why then, the critical IPI never gets registered, so never
detected by the pipeline core in __ipipe_grab_irq. Thanks for the heads
up.
This may make things work a little better:
diff --git a/arch/powerpc/kernel/smp.c b/arch/powerpc/kernel/smp.c
index 8968b24..a4fe229 100644
--- a/arch/powerpc/kernel/smp.c
+++ b/arch/powerpc/kernel/smp.c
@@ -164,16 +164,16 @@ int smp_request_message_ipi(int virq, int msg)
if (msg < 0 || msg > PPC_MSG_DEBUGGER_BREAK) {
return -EINVAL;
}
-#if !defined(CONFIG_DEBUGGER) && !defined(CONFIG_KEXEC)
- if (msg == PPC_MSG_DEBUGGER_BREAK) {
- return 1;
- }
-#endif
#ifdef CONFIG_IPIPE
if (msg == PPC_MSG_DEBUGGER_BREAK)
/* Piggyback the debugger IPI for the I-pipe. */
__ipipe_register_ipi(virq);
#endif
+#if !defined(CONFIG_DEBUGGER) && !defined(CONFIG_KEXEC)
+ if (msg == PPC_MSG_DEBUGGER_BREAK) {
+ return 1;
+ }
+#endif
err = request_irq(virq, smp_ipi_action[msg], IRQF_DISABLED|IRQF_PERCPU,
smp_ipi_name[msg], 0);
--
Philippe.
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