From mboxrd@z Thu Jan 1 00:00:00 1970 From: Stephen Boyd Date: Wed, 18 Feb 2015 23:27:57 +0000 Subject: Re: [PATCH v3] ARM: smp: Only expose /sys/.../cpuX/online if hotpluggable Message-Id: <54E51FFD.7080506@codeaurora.org> List-Id: References: <1423874574-3494-1-git-send-email-sboyd@codeaurora.org> <20150218222731.GC24177@verge.net.au> In-Reply-To: <20150218222731.GC24177@verge.net.au> MIME-Version: 1.0 Content-Type: text/plain; charset="us-ascii" Content-Transfer-Encoding: 7bit To: linux-arm-kernel@lists.infradead.org On 02/18/15 14:27, Simon Horman wrote: > On Fri, Feb 13, 2015 at 04:42:54PM -0800, 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 current users use the op to >> indicate if a CPU can be hotplugged or not in a static fashion. >> With PSCI we may need to introduce 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 1, 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 >> Cc: Simon Horman >> Cc: Magnus Damm >> Cc: >> Signed-off-by: Stephen Boyd >> --- >> >> Changes since v2: >> * Left cpu_disable op in place >> * Split out shmobile function deletion >> >> arch/arm/common/mcpm_platsmp.c | 12 ++++-------- >> arch/arm/include/asm/smp.h | 10 ++++++++++ >> arch/arm/kernel/setup.c | 2 +- >> arch/arm/kernel/smp.c | 15 ++++++++++++++- >> arch/arm/mach-shmobile/common.h | 2 +- >> arch/arm/mach-shmobile/platsmp.c | 4 ++-- >> arch/arm/mach-shmobile/smp-r8a7790.c | 2 +- >> arch/arm/mach-shmobile/smp-r8a7791.c | 2 +- >> arch/arm/mach-shmobile/smp-sh73a0.c | 2 +- >> 9 files changed, 35 insertions(+), 16 deletions(-) > I think it would make sense to separate the ARM-core changes > from the mach-shmobile integration changes. Are you saying two (three?) patches to add the op, and then move over each struct smp_operations? It's all going through rmk's tree so I'll leave that up to him. -- Qualcomm Innovation Center, Inc. is a member of Code Aurora Forum, a Linux Foundation Collaborative Project