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sched/cpuset: Bring back cpuset_mutex

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commit 111cd11bbc54850f24191c52ff217da88a5e639b upstream.

Turns out percpu_cpuset_rwsem - commit 1243dc518c ("cgroup/cpuset:
Convert cpuset_mutex to percpu_rwsem") - wasn't such a brilliant idea,
as it has been reported to cause slowdowns in workloads that need to
change cpuset configuration frequently and it is also not implementing
priority inheritance (which causes troubles with realtime workloads).

Convert percpu_cpuset_rwsem back to regular cpuset_mutex. Also grab it
only for SCHED_DEADLINE tasks (other policies don't care about stable
cpusets anyway).

Signed-off-by: Juri Lelli <juri.lelli@redhat.com>
Reviewed-by: Waiman Long <longman@redhat.com>
Signed-off-by: Tejun Heo <tj@kernel.org>
[ Conflict in kernel/cgroup/cpuset.c due to pulling new code/comments.
  Reject all new code. Remove BUG_ON() about rwsem that doesn't exist on
  mainline. ]
Signed-off-by: Qais Yousef (Google) <qyousef@layalina.io>
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>
This commit is contained in:
Juri Lelli
2023-08-20 16:24:13 +01:00
committed by Greg Kroah-Hartman
parent 7030fbf75f
commit 9bcfe15278
3 changed files with 99 additions and 92 deletions
Download Patch File Download Diff File Expand all files Collapse all files

8
include/linux/cpuset.h
View File

@@ -71,8 +71,8 @@ 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_lock(void);
extern void cpuset_unlock(void);
extern void cpuset_cpus_allowed(struct task_struct *p, struct cpumask *mask);
extern bool cpuset_cpus_allowed_fallback(struct task_struct *p);
extern nodemask_t cpuset_mems_allowed(struct task_struct *p);
@@ -196,8 +196,8 @@ 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_lock(void) { }
static inline void cpuset_unlock(void) { }
static inline void cpuset_cpus_allowed(struct task_struct *p,
struct cpumask *mask)

161
kernel/cgroup/cpuset.c
View File

File diff suppressed because it is too large Load Diff

22
kernel/sched/core.c
View File

@@ -7475,6 +7475,7 @@ static int __sched_setscheduler(struct task_struct *p,
int reset_on_fork;
int queue_flags = DEQUEUE_SAVE | DEQUEUE_MOVE | DEQUEUE_NOCLOCK;
struct rq *rq;
bool cpuset_locked = false;
/* The pi code expects interrupts enabled */
BUG_ON(pi && in_interrupt());
@@ -7524,8 +7525,14 @@ recheck:
return retval;
}
if (pi)
cpuset_read_lock();
/*
* SCHED_DEADLINE bandwidth accounting relies on stable cpusets
* information.
*/
if (dl_policy(policy) || dl_policy(p->policy)) {
cpuset_locked = true;
cpuset_lock();
}
/*
* Make sure no PI-waiters arrive (or leave) while we are
@@ -7601,8 +7608,8 @@ change:
if (unlikely(oldpolicy != -1 && oldpolicy != p->policy)) {
policy = oldpolicy = -1;
task_rq_unlock(rq, p, &rf);
if (pi)
cpuset_read_unlock();
if (cpuset_locked)
cpuset_unlock();
goto recheck;
}
@@ -7669,7 +7676,8 @@ change:
task_rq_unlock(rq, p, &rf);
if (pi) {
cpuset_read_unlock();
if (cpuset_locked)
cpuset_unlock();
rt_mutex_adjust_pi(p);
}
@@ -7681,8 +7689,8 @@ change:
unlock:
task_rq_unlock(rq, p, &rf);
if (pi)
cpuset_read_unlock();
if (cpuset_locked)
cpuset_unlock();
return retval;
}