From 51badebdcf394cc5fd574a524b55b3f6085e5e9c Mon Sep 17 00:00:00 2001 From: Gautham R Shenoy Date: Thu, 26 Nov 2009 09:59:05 +0000 Subject: powerpc/pseries: Serialize cpu hotplug operations during deactivate Vs deallocate Currently the cpu-allocation/deallocation process comprises of two steps: - Set the indicators and to update the device tree with DLPAR node information. - Online/offline the allocated/deallocated CPU. This is achieved by writing to the sysfs tunables "probe" during allocation and "release" during deallocation. At the sametime, the userspace can independently online/offline the CPUs of the system using the sysfs tunable "online". It is quite possible that when a userspace tool offlines a CPU for the purpose of deallocation and is in the process of updating the device tree, some other userspace tool could bring the CPU back online by writing to the "online" sysfs tunable thereby causing the deallocate process to fail. The solution to this is to serialize writes to the "probe/release" sysfs tunable with the writes to the "online" sysfs tunable. This patch employs a mutex to provide this serialization, which is a no-op on all architectures except PPC_PSERIES Signed-off-by: Gautham R Shenoy Acked-by: Vaidyanathan Srinivasan Signed-off-by: Benjamin Herrenschmidt --- drivers/base/cpu.c | 2 ++ 1 file changed, 2 insertions(+) (limited to 'drivers/base/cpu.c') diff --git a/drivers/base/cpu.c b/drivers/base/cpu.c index 7c03af7b84a9..27fd775375b0 100644 --- a/drivers/base/cpu.c +++ b/drivers/base/cpu.c @@ -35,6 +35,7 @@ static ssize_t __ref store_online(struct sys_device *dev, struct sysdev_attribut struct cpu *cpu = container_of(dev, struct cpu, sysdev); ssize_t ret; + cpu_hotplug_driver_lock(); switch (buf[0]) { case '0': ret = cpu_down(cpu->sysdev.id); @@ -49,6 +50,7 @@ static ssize_t __ref store_online(struct sys_device *dev, struct sysdev_attribut default: ret = -EINVAL; } + cpu_hotplug_driver_unlock(); if (ret >= 0) ret = count; -- cgit