• Stephen Boyd's avatar
    ARM: 8392/3: smp: Only expose /sys/.../cpuX/online if hotpluggable · 787047ee
    Stephen Boyd authored
    Writes to /sys/.../cpuX/online fail if we determine the platform
    doesn't support hotplug for that CPU. Furthermore, if the cpu_die
    op isn't specified the system hangs when we try to offline a CPU
    and it comes right back online unexpectedly. Let's figure this
    stuff out before we make the sysfs nodes so that the online file
    doesn't even exist if it isn't (at least sometimes) possible to
    hotplug the CPU.
    
    Add a new 'cpu_can_disable' op and repoint all 'cpu_disable'
    implementations at it because all implementers use the op to
    indicate if a CPU can be hotplugged or not in a static fashion.
    With PSCI we may need to add a 'cpu_disable' op so that the
    secure OS can be migrated off the CPU we're trying to hotplug.
    In this case, the 'cpu_can_disable' op will indicate that all
    CPUs are hotpluggable by returning true, but the 'cpu_disable' op
    will make a PSCI migration call and occasionally fail, denying
    the hotplug of a CPU. This shouldn't be any worse than x86 where
    we may indicate that all CPUs are hotpluggable but occasionally
    we can't offline a CPU due to check_irq_vectors_for_cpu_disable()
    failing to find a CPU to move vectors to.
    
    Cc: Mark Rutland <mark.rutland@arm.com>
    Cc: Nicolas Pitre <nico@linaro.org>
    Cc: Dave Martin <Dave.Martin@arm.com>
    Acked-by: Simon Horman <horms@verge.net.au> [shmobile portion]
    Tested-by: default avatarSimon Horman <horms@verge.net.au>
    Cc: Magnus Damm <magnus.damm@gmail.com>
    Cc: <linux-sh@vger.kernel.org>
    Tested-by: default avatarTyler Baker <tyler.baker@linaro.org>
    Cc: Geert Uytterhoeven <geert@linux-m68k.org>
    Signed-off-by: default avatarStephen Boyd <sboyd@codeaurora.org>
    Signed-off-by: default avatarRussell King <rmk+kernel@arm.linux.org.uk>
    787047ee
smp-r8a7791.c 1.81 KB