From: sboyd@codeaurora.org (Stephen Boyd) Date: Tue, 09 Jun 2015 12:08:28 -0700 Subject: [PATCH v5] ARM: smp: Only expose /sys/.../cpuX/online if hotpluggable In-Reply-To: <20150413134246.GS12732@n2100.arm.linux.org.uk> References: <1428705191-15670-1-git-send-email-sboyd@codeaurora.org> <20150413134246.GS12732@n2100.arm.linux.org.uk> Message-ID: <557739AC.8000903@codeaurora.org> To: linux-arm-kernel@lists.infradead.org List-Id: linux-arm-kernel.lists.infradead.org On 04/13/2015 06:42 AM, Russell King - ARM Linux wrote: > On Fri, Apr 10, 2015 at 03:33:11PM -0700, Stephen Boyd wrote: >> 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 >> Cc: Nicolas Pitre >> Cc: Dave Martin >> Acked-by: Simon Horman [shmobile portion] >> Tested-by: Simon Horman >> Cc: Magnus Damm >> Cc: >> Cc: Tyler Baker >> Cc: Geert Uytterhoeven >> Signed-off-by: Stephen Boyd > Let's see some more acks for this... > Nobody else has acked this so far. Shall I put it in the patch tracker now? Or is there someone more specific we need an ack from? -- Qualcomm Innovation Center, Inc. is a member of Code Aurora Forum, a Linux Foundation Collaborative Project