diff options
| -rw-r--r-- | Documentation/cpusets.txt | 6 | ||||
| -rw-r--r-- | kernel/cpuset.c | 33 |
2 files changed, 39 insertions, 0 deletions
diff --git a/Documentation/cpusets.txt b/Documentation/cpusets.txt index 159e2a0c3e80..76b44290c154 100644 --- a/Documentation/cpusets.txt +++ b/Documentation/cpusets.txt @@ -217,6 +217,12 @@ exclusive cpuset. Also, the use of a Linux virtual file system (vfs) to represent the cpuset hierarchy provides for a familiar permission and name space for cpusets, with a minimum of additional kernel code. +The cpus file in the root (top_cpuset) cpuset is read-only. +It automatically tracks the value of cpu_online_map, using a CPU +hotplug notifier. If and when memory nodes can be hotplugged, +we expect to make the mems file in the root cpuset read-only +as well, and have it track the value of node_online_map. + 1.4 What are exclusive cpusets ? -------------------------------- diff --git a/kernel/cpuset.c b/kernel/cpuset.c index 1a649f2bb9bb..f1dda98bdffe 100644 --- a/kernel/cpuset.c +++ b/kernel/cpuset.c @@ -816,6 +816,10 @@ static int update_cpumask(struct cpuset *cs, char *buf) struct cpuset trialcs; int retval, cpus_unchanged; + /* top_cpuset.cpus_allowed tracks cpu_online_map; it's read-only */ + if (cs == &top_cpuset) + return -EACCES; + trialcs = *cs; retval = cpulist_parse(buf, trialcs.cpus_allowed); if (retval < 0) @@ -2033,6 +2037,33 @@ out: return err; } +/* + * The top_cpuset tracks what CPUs and Memory Nodes are online, + * period. This is necessary in order to make cpusets transparent + * (of no affect) on systems that are actively using CPU hotplug + * but making no active use of cpusets. + * + * This handles CPU hotplug (cpuhp) events. If someday Memory + * Nodes can be hotplugged (dynamically changing node_online_map) + * then we should handle that too, perhaps in a similar way. + */ + +#ifdef CONFIG_HOTPLUG_CPU +static int cpuset_handle_cpuhp(struct notifier_block *nb, + unsigned long phase, void *cpu) +{ + mutex_lock(&manage_mutex); + mutex_lock(&callback_mutex); + + top_cpuset.cpus_allowed = cpu_online_map; + + mutex_unlock(&callback_mutex); + mutex_unlock(&manage_mutex); + + return 0; +} +#endif + /** * cpuset_init_smp - initialize cpus_allowed * @@ -2043,6 +2074,8 @@ void __init cpuset_init_smp(void) { top_cpuset.cpus_allowed = cpu_online_map; top_cpuset.mems_allowed = node_online_map; + + hotcpu_notifier(cpuset_handle_cpuhp, 0); } /** |