diff options
Diffstat (limited to 'kernel/cpuset.c')
| -rw-r--r-- | kernel/cpuset.c | 106 |
1 files changed, 93 insertions, 13 deletions
diff --git a/kernel/cpuset.c b/kernel/cpuset.c index 1b32c2c04c1..8c3c400cce9 100644 --- a/kernel/cpuset.c +++ b/kernel/cpuset.c @@ -240,7 +240,7 @@ static struct super_block *cpuset_sb; * A cpuset can only be deleted if both its 'count' of using tasks * is zero, and its list of 'children' cpusets is empty. Since all * tasks in the system use _some_ cpuset, and since there is always at - * least one task in the system (init, pid == 1), therefore, top_cpuset + * least one task in the system (init), therefore, top_cpuset * always has either children cpusets and/or using tasks. So we don't * need a special hack to ensure that top_cpuset cannot be deleted. * @@ -912,6 +912,10 @@ static int update_nodemask(struct cpuset *cs, char *buf) int fudge; int retval; + /* top_cpuset.mems_allowed tracks node_online_map; it's read-only */ + if (cs == &top_cpuset) + return -EACCES; + trialcs = *cs; retval = nodelist_parse(buf, trialcs.mems_allowed); if (retval < 0) @@ -1221,7 +1225,12 @@ static int attach_task(struct cpuset *cs, char *pidbuf, char **ppathbuf) task_lock(tsk); oldcs = tsk->cpuset; - if (!oldcs) { + /* + * After getting 'oldcs' cpuset ptr, be sure still not exiting. + * If 'oldcs' might be the top_cpuset due to the_top_cpuset_hack + * then fail this attach_task(), to avoid breaking top_cpuset.count. + */ + if (tsk->flags & PF_EXITING) { task_unlock(tsk); mutex_unlock(&callback_mutex); put_task_struct(tsk); @@ -2036,33 +2045,104 @@ out: return err; } +#if defined(CONFIG_HOTPLUG_CPU) || defined(CONFIG_MEMORY_HOTPLUG) /* - * 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. + * If common_cpu_mem_hotplug_unplug(), below, unplugs any CPUs + * or memory nodes, we need to walk over the cpuset hierarchy, + * removing that CPU or node from all cpusets. If this removes the + * last CPU or node from a cpuset, then the guarantee_online_cpus() + * or guarantee_online_mems() code will use that emptied cpusets + * parent online CPUs or nodes. Cpusets that were already empty of + * CPUs or nodes are left empty. + * + * This routine is intentionally inefficient in a couple of regards. + * It will check all cpusets in a subtree even if the top cpuset of + * the subtree has no offline CPUs or nodes. It checks both CPUs and + * nodes, even though the caller could have been coded to know that + * only one of CPUs or nodes needed to be checked on a given call. + * This was done to minimize text size rather than cpu cycles. + * + * Call with both manage_mutex and callback_mutex held. + * + * Recursive, on depth of cpuset subtree. */ -#ifdef CONFIG_HOTPLUG_CPU -static int cpuset_handle_cpuhp(struct notifier_block *nb, - unsigned long phase, void *cpu) +static void guarantee_online_cpus_mems_in_subtree(const struct cpuset *cur) +{ + struct cpuset *c; + + /* Each of our child cpusets mems must be online */ + list_for_each_entry(c, &cur->children, sibling) { + guarantee_online_cpus_mems_in_subtree(c); + if (!cpus_empty(c->cpus_allowed)) + guarantee_online_cpus(c, &c->cpus_allowed); + if (!nodes_empty(c->mems_allowed)) + guarantee_online_mems(c, &c->mems_allowed); + } +} + +/* + * The cpus_allowed and mems_allowed nodemasks in the top_cpuset track + * cpu_online_map and node_online_map. Force the top cpuset to track + * whats online after any CPU or memory node hotplug or unplug event. + * + * To ensure that we don't remove a CPU or node from the top cpuset + * that is currently in use by a child cpuset (which would violate + * the rule that cpusets must be subsets of their parent), we first + * call the recursive routine guarantee_online_cpus_mems_in_subtree(). + * + * Since there are two callers of this routine, one for CPU hotplug + * events and one for memory node hotplug events, we could have coded + * two separate routines here. We code it as a single common routine + * in order to minimize text size. + */ + +static void common_cpu_mem_hotplug_unplug(void) { mutex_lock(&manage_mutex); mutex_lock(&callback_mutex); + guarantee_online_cpus_mems_in_subtree(&top_cpuset); top_cpuset.cpus_allowed = cpu_online_map; + top_cpuset.mems_allowed = node_online_map; mutex_unlock(&callback_mutex); mutex_unlock(&manage_mutex); +} +#endif + +#ifdef CONFIG_HOTPLUG_CPU +/* + * 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 routine ensures that top_cpuset.cpus_allowed tracks + * cpu_online_map on each CPU hotplug (cpuhp) event. + */ +static int cpuset_handle_cpuhp(struct notifier_block *nb, + unsigned long phase, void *cpu) +{ + common_cpu_mem_hotplug_unplug(); return 0; } #endif +#ifdef CONFIG_MEMORY_HOTPLUG +/* + * Keep top_cpuset.mems_allowed tracking node_online_map. + * Call this routine anytime after you change node_online_map. + * See also the previous routine cpuset_handle_cpuhp(). + */ + +void cpuset_track_online_nodes() +{ + common_cpu_mem_hotplug_unplug(); +} +#endif + /** * cpuset_init_smp - initialize cpus_allowed * |