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authorStephen Boyd <sboyd@codeaurora.org>2015-07-29 00:34:48 +0100
committerRussell King <rmk+kernel@arm.linux.org.uk>2015-07-31 18:58:30 +0100
commit787047eea24a2443c366679ae6b5a3873a33b64e (patch)
tree183659ffb653f2203ff81e7a1374973d8e18d251 /arch/arm/kernel/smp.c
parent57853e8906a04a86c32fb96d8421b923c6d64162 (diff)
ARM: 8392/3: smp: Only expose /sys/.../cpuX/online if hotpluggable
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: Simon Horman <horms@verge.net.au> Cc: Magnus Damm <magnus.damm@gmail.com> Cc: <linux-sh@vger.kernel.org> Tested-by: Tyler Baker <tyler.baker@linaro.org> Cc: Geert Uytterhoeven <geert@linux-m68k.org> Signed-off-by: Stephen Boyd <sboyd@codeaurora.org> Signed-off-by: Russell King <rmk+kernel@arm.linux.org.uk>
Diffstat (limited to 'arch/arm/kernel/smp.c')
-rw-r--r--arch/arm/kernel/smp.c15
1 files changed, 14 insertions, 1 deletions
diff --git a/arch/arm/kernel/smp.c b/arch/arm/kernel/smp.c
index 90dfbedfbfb8..3cd846f48eaf 100644
--- a/arch/arm/kernel/smp.c
+++ b/arch/arm/kernel/smp.c
@@ -175,13 +175,26 @@ static int platform_cpu_disable(unsigned int cpu)
if (smp_ops.cpu_disable)
return smp_ops.cpu_disable(cpu);
+ return 0;
+}
+
+int platform_can_hotplug_cpu(unsigned int cpu)
+{
+ /* cpu_die must be specified to support hotplug */
+ if (!smp_ops.cpu_die)
+ return 0;
+
+ if (smp_ops.cpu_can_disable)
+ return smp_ops.cpu_can_disable(cpu);
+
/*
* By default, allow disabling all CPUs except the first one,
* since this is special on a lot of platforms, e.g. because
* of clock tick interrupts.
*/
- return cpu == 0 ? -EPERM : 0;
+ return cpu != 0;
}
+
/*
* __cpu_disable runs on the processor to be shutdown.
*/