From: Juri Lelli <juri.lelli@redhat.com>
To: peterz@infradead.org, mingo@redhat.com, rostedt@goodmis.org,
tj@kernel.org
Cc: linux-kernel@vger.kernel.org, luca.abeni@santannapisa.it,
claudio@evidence.eu.com, tommaso.cucinotta@santannapisa.it,
bristot@redhat.com, mathieu.poirier@linaro.org,
lizefan@huawei.com, longman@redhat.com, dietmar.eggemann@arm.com,
cgroups@vger.kernel.org, Juri Lelli <juri.lelli@redhat.com>
Subject: [PATCH v9 8/8] sched/core: Prevent race condition between cpuset and __sched_setscheduler()
Date: Fri, 19 Jul 2019 16:00:00 +0200 [thread overview]
Message-ID: <20190719140000.31694-9-juri.lelli@redhat.com> (raw)
In-Reply-To: <20190719140000.31694-1-juri.lelli@redhat.com>
No synchronisation mechanism exists between the cpuset subsystem and
calls to function __sched_setscheduler(). As such, it is possible that
new root domains are created on the cpuset side while a deadline
acceptance test is carried out in __sched_setscheduler(), leading to a
potential oversell of CPU bandwidth.
Grab cpuset_rwsem read lock from core scheduler, so to prevent
situations such as the one described above from happening.
The only exception is normalize_rt_tasks() which needs to work under
tasklist_lock and can't therefore grab cpuset_rwsem. We are fine with
this, as this function is only called by sysrq and, if that gets
triggered, DEADLINE guarantees are already gone out of the window
anyway.
Signed-off-by: Juri Lelli <juri.lelli@redhat.com>
---
v8 -> v9:
- Add comment in changelog regarding normalize_rt_tasks() (Peter)
---
include/linux/cpuset.h | 5 +++++
kernel/cgroup/cpuset.c | 11 +++++++++++
kernel/sched/core.c | 33 ++++++++++++++++++++++++++-------
3 files changed, 42 insertions(+), 7 deletions(-)
diff --git a/include/linux/cpuset.h b/include/linux/cpuset.h
index 7f1478c26a33..04c20de66afc 100644
--- a/include/linux/cpuset.h
+++ b/include/linux/cpuset.h
@@ -55,6 +55,8 @@ extern void cpuset_init_smp(void);
extern void cpuset_force_rebuild(void);
extern void cpuset_update_active_cpus(void);
extern void cpuset_wait_for_hotplug(void);
+extern void cpuset_read_lock(void);
+extern void cpuset_read_unlock(void);
extern void cpuset_cpus_allowed(struct task_struct *p, struct cpumask *mask);
extern void cpuset_cpus_allowed_fallback(struct task_struct *p);
extern nodemask_t cpuset_mems_allowed(struct task_struct *p);
@@ -176,6 +178,9 @@ static inline void cpuset_update_active_cpus(void)
static inline void cpuset_wait_for_hotplug(void) { }
+static inline void cpuset_read_lock(void) { }
+static inline void cpuset_read_unlock(void) { }
+
static inline void cpuset_cpus_allowed(struct task_struct *p,
struct cpumask *mask)
{
diff --git a/kernel/cgroup/cpuset.c b/kernel/cgroup/cpuset.c
index 93414ea63252..d16e160a3b35 100644
--- a/kernel/cgroup/cpuset.c
+++ b/kernel/cgroup/cpuset.c
@@ -334,6 +334,17 @@ static struct cpuset top_cpuset = {
*/
DEFINE_STATIC_PERCPU_RWSEM(cpuset_rwsem);
+
+void cpuset_read_lock(void)
+{
+ percpu_down_read(&cpuset_rwsem);
+}
+
+void cpuset_read_unlock(void)
+{
+ percpu_up_read(&cpuset_rwsem);
+}
+
static DEFINE_SPINLOCK(callback_lock);
static struct workqueue_struct *cpuset_migrate_mm_wq;
diff --git a/kernel/sched/core.c b/kernel/sched/core.c
index acd6a9fe85bc..18e151c6b48d 100644
--- a/kernel/sched/core.c
+++ b/kernel/sched/core.c
@@ -4208,6 +4208,9 @@ static int __sched_setscheduler(struct task_struct *p,
return retval;
}
+ if (pi)
+ cpuset_read_lock();
+
/*
* Make sure no PI-waiters arrive (or leave) while we are
* changing the priority of the task:
@@ -4280,6 +4283,8 @@ static int __sched_setscheduler(struct task_struct *p,
if (unlikely(oldpolicy != -1 && oldpolicy != p->policy)) {
policy = oldpolicy = -1;
task_rq_unlock(rq, p, &rf);
+ if (pi)
+ cpuset_read_unlock();
goto recheck;
}
@@ -4338,8 +4343,10 @@ static int __sched_setscheduler(struct task_struct *p,
preempt_disable();
task_rq_unlock(rq, p, &rf);
- if (pi)
+ if (pi) {
+ cpuset_read_unlock();
rt_mutex_adjust_pi(p);
+ }
/* Run balance callbacks after we've adjusted the PI chain: */
balance_callback(rq);
@@ -4349,6 +4356,8 @@ static int __sched_setscheduler(struct task_struct *p,
unlock:
task_rq_unlock(rq, p, &rf);
+ if (pi)
+ cpuset_read_unlock();
return retval;
}
@@ -4433,10 +4442,15 @@ do_sched_setscheduler(pid_t pid, int policy, struct sched_param __user *param)
rcu_read_lock();
retval = -ESRCH;
p = find_process_by_pid(pid);
- if (p != NULL)
- retval = sched_setscheduler(p, policy, &lparam);
+ if (!p) {
+ rcu_read_unlock();
+ goto exit;
+ }
+ get_task_struct(p);
rcu_read_unlock();
-
+ retval = sched_setscheduler(p, policy, &lparam);
+ put_task_struct(p);
+exit:
return retval;
}
@@ -4564,10 +4578,15 @@ SYSCALL_DEFINE3(sched_setattr, pid_t, pid, struct sched_attr __user *, uattr,
rcu_read_lock();
retval = -ESRCH;
p = find_process_by_pid(pid);
- if (p != NULL)
- retval = sched_setattr(p, &attr);
+ if (!p) {
+ rcu_read_unlock();
+ goto exit;
+ }
+ get_task_struct(p);
rcu_read_unlock();
-
+ retval = sched_setattr(p, &attr);
+ put_task_struct(p);
+exit:
return retval;
}
--
2.17.2
next prev parent reply other threads:[~2019-07-19 14:00 UTC|newest]
Thread overview: 42+ messages / expand[flat|nested] mbox.gz Atom feed top
2019-07-19 13:59 [PATCH v9 0/8] sched/deadline: fix cpusets bandwidth accounting Juri Lelli
2019-07-19 13:59 ` [PATCH v9 1/8] sched/topology: Adding function partition_sched_domains_locked() Juri Lelli
2019-07-25 16:19 ` [tip:sched/core] sched/topology: Add partition_sched_domains_locked() tip-bot for Mathieu Poirier
2019-07-19 13:59 ` [PATCH v9 2/8] sched/core: Streamlining calls to task_rq_unlock() Juri Lelli
2019-07-22 8:21 ` Dietmar Eggemann
2019-07-22 8:32 ` Juri Lelli
2019-07-22 9:08 ` Dietmar Eggemann
2019-07-23 10:32 ` Peter Zijlstra
2019-07-23 10:31 ` Peter Zijlstra
2019-07-23 13:11 ` Tejun Heo
2019-07-23 14:58 ` Juri Lelli
2019-07-25 16:20 ` [tip:sched/core] sched/core: Streamle " tip-bot for Mathieu Poirier
2019-07-19 13:59 ` [PATCH v9 3/8] cpuset: Rebuild root domain deadline accounting information Juri Lelli
2019-07-25 13:53 ` Ingo Molnar
2019-07-25 13:56 ` Ingo Molnar
2019-07-25 14:07 ` Juri Lelli
2019-07-25 16:00 ` Mathieu Poirier
2019-07-25 16:21 ` [tip:sched/core] cpusets: " tip-bot for Mathieu Poirier
2019-11-04 18:57 ` [PATCH v9 3/8] cpuset: " Michal Koutný
2019-11-05 12:03 ` Michal Koutný
2022-12-16 23:35 ` Qais Yousef
2022-12-17 2:26 ` Waiman Long
2022-12-17 22:10 ` Qais Yousef
2022-12-19 8:07 ` Vincent Guittot
2022-12-20 11:43 ` Qais Yousef
2023-01-15 16:41 ` Qais Yousef
2019-07-19 13:59 ` [PATCH v9 4/8] sched/deadline: Fix bandwidth accounting at all levels after offline migration Juri Lelli
2019-07-22 11:07 ` Dietmar Eggemann
2019-07-22 12:28 ` Juri Lelli
2019-07-22 13:21 ` Dietmar Eggemann
2019-07-22 13:35 ` Juri Lelli
2019-07-22 14:29 ` Dietmar Eggemann
2019-07-25 16:21 ` [tip:sched/core] " tip-bot for Juri Lelli
2019-07-19 13:59 ` [PATCH v9 5/8] cgroup/cpuset: convert cpuset_mutex to percpu_rwsem Juri Lelli
2019-07-25 16:22 ` [tip:sched/core] cgroup/cpuset: Convert " tip-bot for Juri Lelli
2019-07-19 13:59 ` [PATCH v9 6/8] cgroup/cpuset: Change cpuset_rwsem and hotplug lock order Juri Lelli
2019-07-25 16:23 ` [tip:sched/core] " tip-bot for Juri Lelli
2019-07-19 13:59 ` [PATCH v9 7/8] rcu/tree: Setschedule gp ktread to SCHED_FIFO outside of atomic region Juri Lelli
2019-07-25 16:24 ` [tip:sched/core] rcu/tree: Call setschedule() " tip-bot for Juri Lelli
2019-07-19 14:00 ` Juri Lelli [this message]
2019-07-25 16:24 ` [tip:sched/core] sched/core: Prevent race condition between cpuset and __sched_setscheduler() tip-bot for Juri Lelli
2019-07-24 8:45 ` [PATCH v9 0/8] sched/deadline: fix cpusets bandwidth accounting Dietmar Eggemann
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