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

[Russell King - ARM Linux]

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.