[PATCH] Add call to non-crashing cores through IPI

[Per Fransson]

On Mon, Nov 22, 2010 at 12:27 PM, Russell King - ARM Linux
<linux at arm.linux.org.uk> wrote:
> On Mon, Nov 22, 2010 at 10:47:40AM +0000, Russell King - ARM Linux wrote:
>> However, we do need smp_send_stop() to wait for a limited time for the
>> other CPUs to respond to the request.
>
> ARM: smp: make smp_send_stop() wait for secondary CPUs to stop
>
> Wait up to one second for secondary CPUs to respond to a request to
> stop.  This avoids the sender CPU continuing and possibly destroying
> state before the recipients have had a chance to respond to the stop.
> However, if the recipients have crashed, we won't hang the sender
> CPU indefinitely.
>

The point of the crash kernel functionality is to make it possible to grab a
snapshot of the system at the time of the crash. smp_send_stop() will
take the other cores offline, which makes the snapshot differ from the
crash state more than it has to. To be more concrete, any core dump
analysis tool which reads the cpu_online_mask to determine the number
of cpus in use will get an incorrect picture.

Regards,
Per