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authorPaul Jackson <pj@sgi.com>2006-08-27 04:23:51 -0400
committerLinus Torvalds <torvalds@g5.osdl.org>2006-08-27 14:01:32 -0400
commit4c4d50f7b39cc58f1064b93a61ad617451ae41df (patch)
treed55ec85fd917472e9859a17e34f8114a7e87892b /kernel/cpuset.c
parent6394cca54894f6a9bcf927ab78d28985944298ff (diff)
[PATCH] cpuset: top_cpuset tracks hotplug changes to cpu_online_map
Change the list of cpus allowed to tasks in the top (root) cpuset to dynamically track what cpus are online, using a CPU hotplug notifier. Make this top cpus file read-only. On systems that have cpusets configured in their kernel, but that aren't actively using cpusets (for some distros, this covers the majority of systems) all tasks end up in the top cpuset. If that system does support CPU hotplug, then these tasks cannot make use of CPUs that are added after system boot, because the CPUs are not allowed in the top cpuset. This is a surprising regression over earlier kernels that didn't have cpusets enabled. In order to keep the behaviour of cpusets consistent between systems actively making use of them and systems not using them, this patch changes the behaviour of the 'cpus' file in the top (root) cpuset, making it read only, and making it automatically track the value of cpu_online_map. Thus tasks in the top cpuset will have automatic use of hot plugged CPUs allowed by their cpuset. Thanks to Anton Blanchard and Nathan Lynch for reporting this problem, driving the fix, and earlier versions of this patch. Signed-off-by: Paul Jackson <pj@sgi.com> Cc: Nathan Lynch <ntl@pobox.com> Cc: Anton Blanchard <anton@samba.org> Signed-off-by: Andrew Morton <akpm@osdl.org> Signed-off-by: Linus Torvalds <torvalds@osdl.org>
Diffstat (limited to 'kernel/cpuset.c')
-rw-r--r--kernel/cpuset.c33
1 files changed, 33 insertions, 0 deletions
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)
816 struct cpuset trialcs; 816 struct cpuset trialcs;
817 int retval, cpus_unchanged; 817 int retval, cpus_unchanged;
818 818
819 /* top_cpuset.cpus_allowed tracks cpu_online_map; it's read-only */
820 if (cs == &top_cpuset)
821 return -EACCES;
822
819 trialcs = *cs; 823 trialcs = *cs;
820 retval = cpulist_parse(buf, trialcs.cpus_allowed); 824 retval = cpulist_parse(buf, trialcs.cpus_allowed);
821 if (retval < 0) 825 if (retval < 0)
@@ -2033,6 +2037,33 @@ out:
2033 return err; 2037 return err;
2034} 2038}
2035 2039
2040/*
2041 * The top_cpuset tracks what CPUs and Memory Nodes are online,
2042 * period. This is necessary in order to make cpusets transparent
2043 * (of no affect) on systems that are actively using CPU hotplug
2044 * but making no active use of cpusets.
2045 *
2046 * This handles CPU hotplug (cpuhp) events. If someday Memory
2047 * Nodes can be hotplugged (dynamically changing node_online_map)
2048 * then we should handle that too, perhaps in a similar way.
2049 */
2050
2051#ifdef CONFIG_HOTPLUG_CPU
2052static int cpuset_handle_cpuhp(struct notifier_block *nb,
2053 unsigned long phase, void *cpu)
2054{
2055 mutex_lock(&manage_mutex);
2056 mutex_lock(&callback_mutex);
2057
2058 top_cpuset.cpus_allowed = cpu_online_map;
2059
2060 mutex_unlock(&callback_mutex);
2061 mutex_unlock(&manage_mutex);
2062
2063 return 0;
2064}
2065#endif
2066
2036/** 2067/**
2037 * cpuset_init_smp - initialize cpus_allowed 2068 * cpuset_init_smp - initialize cpus_allowed
2038 * 2069 *
@@ -2043,6 +2074,8 @@ void __init cpuset_init_smp(void)
2043{ 2074{
2044 top_cpuset.cpus_allowed = cpu_online_map; 2075 top_cpuset.cpus_allowed = cpu_online_map;
2045 top_cpuset.mems_allowed = node_online_map; 2076 top_cpuset.mems_allowed = node_online_map;
2077
2078 hotcpu_notifier(cpuset_handle_cpuhp, 0);
2046} 2079}
2047 2080
2048/** 2081/**