• Stephen Warren's avatar
    ARM: 7759/1: decouple CPU offlining from reboot/shutdown · 19ab428f
    Stephen Warren authored
    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: default avatarRussell King <rmk+kernel@arm.linux.org.uk>
    Signed-off-by: default avatarStephen Warren <swarren@nvidia.com>
    Acked-by: default avatarWill Deacon <will.deacon@arm.com>
    Tested-by: default avatarZhangfei Gao <zhangfei.gao@gmail.com>
    Signed-off-by: default avatarRussell King <rmk+kernel@arm.linux.org.uk>
    19ab428f
smp.c 16.7 KB