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Date: Fri, 1 Jan 2016 12:08:04 +0000
From: "Chen, Yu C" <yu.c.chen@...el.com>
To: "cgroups@...r.kernel.org" <cgroups@...r.kernel.org>
CC: "linux-kernel@...r.kernel.org" <linux-kernel@...r.kernel.org>
Subject: RE: [PATCH] cpuset: fix cpus_allowed mask for offline/online CPUs
Previous one seems to be dropped by maillist so I resend it,
sorry for any inconvenience and happy new year : - )
thanks,
Yu
> -----Original Message-----
> From: Chen, Yu C
> Sent: Friday, January 01, 2016 8:09 PM
> To: cgroups@...r.kernel.org
> Cc: linux-kernel@...r.kernel.org; Chen, Yu C; Vlastimil Babka; Rik van Riel;
> Joonsoo Kim; David Rientjes; Vishnu Pratap Singh; Pintu Kumar; Michal
> Nazarewicz; Mel Gorman; Gortmaker, Paul (Wind River); Peter Zijlstra; Tim
> Chen; Hugh Dickins; Li Zefan; Tejun Heo
> Subject: [PATCH] cpuset: fix cpus_allowed mask for offline/online CPUs
>
> 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@...e.cz>
> Cc: Rik van Riel <riel@...hat.com>
> Cc: Joonsoo Kim <iamjoonsoo.kim@....com>
> Cc: David Rientjes <rientjes@...gle.com>
> Cc: Vishnu Pratap Singh <vishnu.ps@...sung.com>
> Cc: Pintu Kumar <pintu.k@...sung.com>
> Cc: Michal Nazarewicz <mina86@...a86.com>
> Cc: Mel Gorman <mgorman@...e.de>
> Cc: Paul Gortmaker <paul.gortmaker@...driver.com>
> Cc: Peter Zijlstra <peterz@...radead.org>
> Cc: Tim Chen <tim.c.chen@...ux.intel.com>
> Cc: Hugh Dickins <hughd@...gle.com>
> Cc: Li Zefan <lizefan@...wei.com>
> Cc: Tejun Heo <tj@...nel.org>
> Cc: cgroups@...r.kernel.org
> Signed-off-by: Chen Yu <yu.c.chen@...el.com>
> ---
> 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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