ARM: 7759/1: decouple CPU offlining from reboot/shutdown
authorStephen Warren <swarren@nvidia.com>
Fri, 14 Jun 2013 15:14:14 +0000 (16:14 +0100)
committerRussell King <rmk+kernel@arm.linux.org.uk>
Mon, 17 Jun 2013 20:35:25 +0000 (21:35 +0100)
commit19ab428f4b7988ef3ac727c680efc193ef53ce14
tree7cdce88e40ca449db2fea719b88a423f884e1157
parent69f91ff8c93c778cb65b71d9b2d95ff62956354f
ARM: 7759/1: decouple CPU offlining from reboot/shutdown

Add comments to machine_shutdown()/halt()/power_off()/restart() that
describe their purpose and/or requirements re: CPUs being active/not.

In machine_shutdown(), replace the call to smp_send_stop() with a call to
disable_nonboot_cpus(). This completely disables all but one CPU, thus
satisfying the requirement that only a single CPU be active for kexec.
Adjust Kconfig dependencies for this change.

In machine_halt()/power_off()/restart(), call smp_send_stop() directly,
rather than via machine_shutdown(); these functions don't need to
completely de-activate all CPUs using hotplug, but rather just quiesce
them.

Remove smp_kill_cpus(), and its call from smp_send_stop().
smp_kill_cpus() was indirectly calling smp_ops.cpu_kill() without calling
smp_ops.cpu_die() on the target CPUs first. At least some implementations
of smp_ops had issues with this; it caused cpu_kill() to hang on Tegra,
for example. Since smp_send_stop() is only used for shutdown, halt, and
power-off, there is no need to attempt any kind of CPU hotplug here.

Adjust Kconfig to reflect that machine_shutdown() (and hence kexec)
relies upon disable_nonboot_cpus(). However, this alone doesn't guarantee
that hotplug will work, or even that hotplug is implemented for a
particular piece of HW that a multi-platform zImage runs on. Hence, add
error-checking to machine_kexec() to determine whether it did work.

Suggested-by: Russell King <rmk+kernel@arm.linux.org.uk>
Signed-off-by: Stephen Warren <swarren@nvidia.com>
Acked-by: Will Deacon <will.deacon@arm.com>
Tested-by:  Zhangfei Gao <zhangfei.gao@gmail.com>
Signed-off-by: Russell King <rmk+kernel@arm.linux.org.uk>
arch/arm/Kconfig
arch/arm/kernel/machine_kexec.c
arch/arm/kernel/process.c
arch/arm/kernel/smp.c