Messages in this thread | | | From | Keith Owens <> | Subject | Re: [patch] serial console vs NMI watchdog | Date | Mon, 12 Mar 2001 16:52:07 +1100 |
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On Sun, 11 Mar 2001 20:43:16 -0800, george anzinger <george@mvista.com> wrote: >Consider this. Why not use the NMI to sync the cpus. Kdb would have a >function that is called each NMI.
kdb uses NMI IPI to get the other cpu's attention. One cpu is in control and may or may not be accepting NMI, it depends on the event that entered kdb. The other cpus end up in kdb code, spinning waiting for a cpu switch. Initially they are not receiving NMI because they were invoked via NMI which is masked until they exit. However if the user does a cpu switch then single steps the interrupted code, the cpu has to return from the NMI handler to the interrupted code at which time this cpu starts receiving NMI again.
The kdb context can change from ignoring NMI to accepting NMI. It is easier to bring all the cpus into kdb and let the kdb code decide if it ignores any NMI that is being received.
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