Commit be4c9dd7aee5 ("cpuset: enable onlined cpu/node in effective masks")
leverages cpuset's cpus_allowed and its parent's effective_cpus to calculate
the new_cpus by:
cpumask_and(&new_cpus, cs->cpus_allowed, parent_cs(cs)->effective_cpus);
However cpus_allowed will also be updated after the CPU is offline, in
hotplug_update_tasks_legacy, so when the CPU is online again, it will use
the old cpus_allowed mask to calculate the new_cpus, thus new_cpus will get
incorrect value after each round of offline/online.
This problem is found on ubuntu 15.10 with cpuset mounted:
1. echo 0 > /sys/devices/system/cpu/cpu2/online
2. echo 1 > /sys/devices/system/cpu/cpu2/online
3. cat /sys/fs/cgroup/cpuset/cpuset.cpus
0-3
4. cat /sys/fs/cgroup/cpuset/user.slice/cpuset.cpus
0-1,3
5. taskset -c 2 ls
taskset: failed to set pid 0's affinity: Invalid argument
This patch works around this problem by introducing a new
mask cpumask_var_t cpus_sysfs inside struct cpuset,
which will only be updated by writing value to sysfs.cpuset.cpus,
and CPU offline/online will use this mask to set the new cpumask
for a cpuset.
Cc: Vlastimil Babka <vbabka@xxxxxxx>
Cc: Rik van Riel <riel@xxxxxxxxxx>
Cc: Joonsoo Kim <iamjoonsoo.kim@xxxxxxx>
Cc: David Rientjes <rientjes@xxxxxxxxxx>
Cc: Vishnu Pratap Singh <vishnu.ps@xxxxxxxxxxx>
Cc: Pintu Kumar <pintu.k@xxxxxxxxxxx>
Cc: Michal Nazarewicz <mina86@xxxxxxxxxx>
Cc: Mel Gorman <mgorman@xxxxxxx>
Cc: Paul Gortmaker <paul.gortmaker@xxxxxxxxxxxxx>
Cc: Peter Zijlstra <peterz@xxxxxxxxxxxxx>
Cc: Tim Chen <tim.c.chen@xxxxxxxxxxxxxxx>
Cc: Hugh Dickins <hughd@xxxxxxxxxx>
Cc: Li Zefan <lizefan@xxxxxxxxxx>
Cc: Tejun Heo <tj@xxxxxxxxxx>
Cc: cgroups@xxxxxxxxxxxxxxx
Signed-off-by: Chen Yu <yu.c.chen@xxxxxxxxx>
---
kernel/cpuset.c | 24 +++++++++++++++++++++++-
1 file changed, 23 insertions(+), 1 deletion(-)
diff --git a/kernel/cpuset.c b/kernel/cpuset.c
index 02a8ea5..49c9cd5 100644
--- a/kernel/cpuset.c
+++ b/kernel/cpuset.c
@@ -106,6 +106,12 @@ struct cpuset {
nodemask_t effective_mems;
/*
+ * This cpumask can only be modified by sysfs - cpuset.cpus,
+ * and will not change during cpu online/offline.
+ */
+ cpumask_var_t cpus_sysfs;
+
+ /*
* This is old Memory Nodes tasks took on.
*
* - top_cpuset.old_mems_allowed is initialized to mems_allowed.
@@ -963,6 +969,7 @@ static int update_cpumask(struct cpuset *cs, struct cpuset *trialcs,
spin_lock_irq(&callback_lock);
cpumask_copy(cs->cpus_allowed, trialcs->cpus_allowed);
+ cpumask_copy(cs->cpus_sysfs, trialcs->cpus_allowed);
spin_unlock_irq(&callback_lock);
/* use trialcs->cpus_allowed as a temp variable */
@@ -1922,17 +1929,22 @@ cpuset_css_alloc(struct cgroup_subsys_state *parent_css)
goto free_cs;
if (!alloc_cpumask_var(&cs->effective_cpus, GFP_KERNEL))
goto free_cpus;
+ if (!alloc_cpumask_var(&cs->cpus_sysfs, GFP_KERNEL))
+ goto free_effective;
set_bit(CS_SCHED_LOAD_BALANCE, &cs->flags);
cpumask_clear(cs->cpus_allowed);
nodes_clear(cs->mems_allowed);
cpumask_clear(cs->effective_cpus);
nodes_clear(cs->effective_mems);
+ cpumask_clear(cs->cpus_sysfs);
fmeter_init(&cs->fmeter);
cs->relax_domain_level = -1;
return &cs->css;
+free_effective:
+ free_cpumask_var(cs->effective_cpus);
free_cpus:
free_cpumask_var(cs->cpus_allowed);
free_cs:
@@ -1997,6 +2009,7 @@ static int cpuset_css_online(struct cgroup_subsys_state *css)
cs->effective_mems = parent->mems_allowed;
cpumask_copy(cs->cpus_allowed, parent->cpus_allowed);
cpumask_copy(cs->effective_cpus, parent->cpus_allowed);
+ cpumask_copy(cs->cpus_sysfs, parent->cpus_allowed);
spin_unlock_irq(&callback_lock);
out_unlock:
mutex_unlock(&cpuset_mutex);
@@ -2030,6 +2043,7 @@ static void cpuset_css_free(struct cgroup_subsys_state *css)
free_cpumask_var(cs->effective_cpus);
free_cpumask_var(cs->cpus_allowed);
+ free_cpumask_var(cs->cpus_sysfs);
kfree(cs);
}
@@ -2078,11 +2092,14 @@ int __init cpuset_init(void)
BUG();
if (!alloc_cpumask_var(&top_cpuset.effective_cpus, GFP_KERNEL))
BUG();
+ if (!alloc_cpumask_var(&top_cpuset.cpus_sysfs, GFP_KERNEL))
+ BUG();
cpumask_setall(top_cpuset.cpus_allowed);
nodes_setall(top_cpuset.mems_allowed);
cpumask_setall(top_cpuset.effective_cpus);
nodes_setall(top_cpuset.effective_mems);
+ cpumask_setall(top_cpuset.cpus_sysfs);
fmeter_init(&top_cpuset.fmeter);
set_bit(CS_SCHED_LOAD_BALANCE, &top_cpuset.flags);
@@ -2213,7 +2230,10 @@ retry:
goto retry;
}
- cpumask_and(&new_cpus, cs->cpus_allowed, parent_cs(cs)->effective_cpus);
+ if (cgroup_subsys_on_dfl(cpuset_cgrp_subsys))
+ cpumask_and(&new_cpus, cs->cpus_allowed, parent_cs(cs)->effective_cpus);
+ else
+ cpumask_and(&new_cpus, cs->cpus_sysfs, parent_cs(cs)->effective_cpus);
nodes_and(new_mems, cs->mems_allowed, parent_cs(cs)->effective_mems);
cpus_updated = !cpumask_equal(&new_cpus, cs->effective_cpus);
@@ -2354,6 +2374,8 @@ void __init cpuset_init_smp(void)
cpumask_copy(top_cpuset.effective_cpus, cpu_active_mask);
top_cpuset.effective_mems = node_states[N_MEMORY];
+ cpumask_copy(top_cpuset.cpus_sysfs, cpu_active_mask);
+
register_hotmemory_notifier(&cpuset_track_online_nodes_nb);
}
--
1.8.4.2
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