From mboxrd@z Thu Jan 1 00:00:00 1970 From: Simon Horman Date: Thu, 19 Feb 2015 22:14:56 +0000 Subject: Re: [PATCH v3] ARM: smp: Only expose /sys/.../cpuX/online if hotpluggable Message-Id: <20150219221456.GC617@verge.net.au> List-Id: References: <1423874574-3494-1-git-send-email-sboyd@codeaurora.org> <20150218222731.GC24177@verge.net.au> <54E51FFD.7080506@codeaurora.org> In-Reply-To: <54E51FFD.7080506@codeaurora.org> MIME-Version: 1.0 Content-Type: text/plain; charset="us-ascii" Content-Transfer-Encoding: 7bit To: linux-arm-kernel@lists.infradead.org On Wed, Feb 18, 2015 at 03:27:57PM -0800, Stephen Boyd wrote: > 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. I'm also happy to let RMK to decide what he thinks is best.