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

[Per Fransson]

On the other hand, do we really need to enable the interrupts before
performing an ipi?
The important thing must be for them to be enabled on the
receiving/callee cores. It's not
as if we want the crashing core to be interruptable, is it?

I tried it and it seems to work fine.

/Per

On Mon, Nov 22, 2010 at 3:40 PM, Russell King - ARM Linux
<linux at arm.linux.org.uk> wrote:
> On Mon, Nov 22, 2010 at 03:31:24PM +0100, Per Fransson wrote:
>> 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.
>
> Well, you can't go around randomly enabling interrupts to call functions
> that require interrupts to be enabled, so I guess it's not possible to
> save the state of the other cores.
>
> I guess you're going to have to come up with another solution.
>