Xen devel - Jul 2009 - [RFC] [PATCH] One watchdog trips the watchdog on all processors

I''ve been using the watchdog timer recently to debug deadlocks, and
found that it only triggers on one cpu.  Unfortunately, if your
deadlock is not symmetric, it''s not often obvious what the other
cpu(s) is(are) doing.  The attached patch is a hack I put in place to
trigger an NMI on all cpus if it''s triggered on one.  This will cause
things to hang instead of reboot, however, so I''m not sure how to
integrate it into the normal watchdog-for-reliability functionality
(as opposed to watchdog-for-debugging).

 -George


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>>> George Dunlap <dunlapg@umich.edu> 17.07.09 14:55 >>>
>...
>+static void do_nmi_trigger_cpu(int cpu)
>+{
>+    u32 id = cpu_physical_id(cpu);
>+
>+    printk("Triggering NMI on APIC ID %x\n", id);
>+    debugtrace_dump();
>+
>+    local_irq_disable();
>+    apic_wait_icr_idle();
>+    apic_icr_write(APIC_DM_NMI | APIC_DEST_PHYSICAL, id);
>+    local_irq_enable();
You definitely don''t want to enable interrupts inside an NMI. I
don''t think
you need to disable them either, as nothing else should have enabled
them.
>...
>+                for_each_cpu(cpu)
This is for_each_possible_cpu() now.

Jan


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