This is a note to let you know that I've just added the patch titled
cgroup/cpuset: Change cpuset_rwsem and hotplug lock order
to the 4.19-stable tree which can be found at:
http://www.kernel.org/git/?p=linux/kernel/git/stable/stable-queue.git;a=summary
The filename of the patch is:
cgroup-cpuset-change-cpuset_rwsem-and-hotplug-lock-order.patch
and it can be found in the queue-4.19 subdirectory.
If you, or anyone else, feels it should not be added to the stable tree,
please let <stable@xxxxxxxxxxxxxxx> know about it.
>From d74b27d63a8bebe2fe634944e4ebdc7b10db7a39 Mon Sep 17 00:00:00 2001
From: Juri Lelli <juri.lelli@xxxxxxxxxx>
Date: Fri, 19 Jul 2019 15:59:58 +0200
Subject: cgroup/cpuset: Change cpuset_rwsem and hotplug lock order
From: Juri Lelli <juri.lelli@xxxxxxxxxx>
commit d74b27d63a8bebe2fe634944e4ebdc7b10db7a39 upstream.
cpuset_rwsem is going to be acquired from sched_setscheduler() with a
following patch. There are however paths (e.g., spawn_ksoftirqd) in
which sched_scheduler() is eventually called while holding hotplug lock;
this creates a dependecy between hotplug lock (to be always acquired
first) and cpuset_rwsem (to be always acquired after hotplug lock).
Fix paths which currently take the two locks in the wrong order (after
a following patch is applied).
Tested-by: Dietmar Eggemann <dietmar.eggemann@xxxxxxx>
Signed-off-by: Juri Lelli <juri.lelli@xxxxxxxxxx>
Signed-off-by: Peter Zijlstra (Intel) <peterz@xxxxxxxxxxxxx>
Cc: Linus Torvalds <torvalds@xxxxxxxxxxxxxxxxxxxx>
Cc: Peter Zijlstra <peterz@xxxxxxxxxxxxx>
Cc: Thomas Gleixner <tglx@xxxxxxxxxxxxx>
Cc: bristot@xxxxxxxxxx
Cc: claudio@xxxxxxxxxxxxxxx
Cc: lizefan@xxxxxxxxxx
Cc: longman@xxxxxxxxxx
Cc: luca.abeni@xxxxxxxxxxxxxxx
Cc: mathieu.poirier@xxxxxxxxxx
Cc: rostedt@xxxxxxxxxxx
Cc: tj@xxxxxxxxxx
Cc: tommaso.cucinotta@xxxxxxxxxxxxxxx
Link: https://lkml.kernel.org/r/20190719140000.31694-7-juri.lelli@xxxxxxxxxx
Signed-off-by: Ingo Molnar <mingo@xxxxxxxxxx>
Signed-off-by: Cai Xinchen <caixinchen1@xxxxxxxxxx>
Signed-off-by: Greg Kroah-Hartman <gregkh@xxxxxxxxxxxxxxxxxxx>
---
include/linux/cpuset.h | 8 ++++----
kernel/cgroup/cpuset.c | 18 ++++++++++++++----
2 files changed, 18 insertions(+), 8 deletions(-)
--- a/include/linux/cpuset.h
+++ b/include/linux/cpuset.h
@@ -40,14 +40,14 @@ static inline bool cpusets_enabled(void)
static inline void cpuset_inc(void)
{
- static_branch_inc(&cpusets_pre_enable_key);
- static_branch_inc(&cpusets_enabled_key);
+ static_branch_inc_cpuslocked(&cpusets_pre_enable_key);
+ static_branch_inc_cpuslocked(&cpusets_enabled_key);
}
static inline void cpuset_dec(void)
{
- static_branch_dec(&cpusets_enabled_key);
- static_branch_dec(&cpusets_pre_enable_key);
+ static_branch_dec_cpuslocked(&cpusets_enabled_key);
+ static_branch_dec_cpuslocked(&cpusets_pre_enable_key);
}
extern int cpuset_init(void);
--- a/kernel/cgroup/cpuset.c
+++ b/kernel/cgroup/cpuset.c
@@ -830,8 +830,8 @@ static void rebuild_sched_domains_locked
cpumask_var_t *doms;
int ndoms;
+ lockdep_assert_cpus_held();
lockdep_assert_held(&cpuset_mutex);
- get_online_cpus();
/*
* We have raced with CPU hotplug. Don't do anything to avoid
@@ -839,15 +839,13 @@ static void rebuild_sched_domains_locked
* Anyways, hotplug work item will rebuild sched domains.
*/
if (!cpumask_equal(top_cpuset.effective_cpus, cpu_active_mask))
- goto out;
+ return;
/* Generate domain masks and attrs */
ndoms = generate_sched_domains(&doms, &attr);
/* Have scheduler rebuild the domains */
partition_sched_domains(ndoms, doms, attr);
-out:
- put_online_cpus();
}
#else /* !CONFIG_SMP */
static void rebuild_sched_domains_locked(void)
@@ -857,9 +855,11 @@ static void rebuild_sched_domains_locked
void rebuild_sched_domains(void)
{
+ get_online_cpus();
mutex_lock(&cpuset_mutex);
rebuild_sched_domains_locked();
mutex_unlock(&cpuset_mutex);
+ put_online_cpus();
}
/**
@@ -1617,6 +1617,7 @@ static int cpuset_write_u64(struct cgrou
cpuset_filetype_t type = cft->private;
int retval = 0;
+ get_online_cpus();
mutex_lock(&cpuset_mutex);
if (!is_cpuset_online(cs)) {
retval = -ENODEV;
@@ -1654,6 +1655,7 @@ static int cpuset_write_u64(struct cgrou
}
out_unlock:
mutex_unlock(&cpuset_mutex);
+ put_online_cpus();
return retval;
}
@@ -1664,6 +1666,7 @@ static int cpuset_write_s64(struct cgrou
cpuset_filetype_t type = cft->private;
int retval = -ENODEV;
+ get_online_cpus();
mutex_lock(&cpuset_mutex);
if (!is_cpuset_online(cs))
goto out_unlock;
@@ -1678,6 +1681,7 @@ static int cpuset_write_s64(struct cgrou
}
out_unlock:
mutex_unlock(&cpuset_mutex);
+ put_online_cpus();
return retval;
}
@@ -1716,6 +1720,7 @@ static ssize_t cpuset_write_resmask(stru
kernfs_break_active_protection(of->kn);
flush_work(&cpuset_hotplug_work);
+ get_online_cpus();
mutex_lock(&cpuset_mutex);
if (!is_cpuset_online(cs))
goto out_unlock;
@@ -1741,6 +1746,7 @@ static ssize_t cpuset_write_resmask(stru
free_trial_cpuset(trialcs);
out_unlock:
mutex_unlock(&cpuset_mutex);
+ put_online_cpus();
kernfs_unbreak_active_protection(of->kn);
css_put(&cs->css);
flush_workqueue(cpuset_migrate_mm_wq);
@@ -1985,6 +1991,7 @@ static int cpuset_css_online(struct cgro
if (!parent)
return 0;
+ get_online_cpus();
mutex_lock(&cpuset_mutex);
set_bit(CS_ONLINE, &cs->flags);
@@ -2035,6 +2042,7 @@ static int cpuset_css_online(struct cgro
spin_unlock_irq(&callback_lock);
out_unlock:
mutex_unlock(&cpuset_mutex);
+ put_online_cpus();
return 0;
}
@@ -2048,6 +2056,7 @@ static void cpuset_css_offline(struct cg
{
struct cpuset *cs = css_cs(css);
+ get_online_cpus();
mutex_lock(&cpuset_mutex);
if (is_sched_load_balance(cs))
@@ -2057,6 +2066,7 @@ static void cpuset_css_offline(struct cg
clear_bit(CS_ONLINE, &cs->flags);
mutex_unlock(&cpuset_mutex);
+ put_online_cpus();
}
static void cpuset_css_free(struct cgroup_subsys_state *css)
Patches currently in stable-queue which might be from juri.lelli@xxxxxxxxxx are
queue-4.19/cgroup-cpuset-change-cpuset_rwsem-and-hotplug-lock-order.patch
