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author | Juri Lelli <juri.lelli@redhat.com> | 2019-07-19 16:00:00 +0200 |
---|---|---|
committer | Ingo Molnar <mingo@kernel.org> | 2019-07-25 15:55:04 +0200 |
commit | 710da3c8ea7dfbd327920afd3831d8c82c42789d (patch) | |
tree | 146d69299e74b9c9fe0e23a0588484543ccec8f1 /kernel/cgroup | |
parent | rcu/tree: Call setschedule() gp ktread to SCHED_FIFO outside of atomic region (diff) | |
download | linux-710da3c8ea7dfbd327920afd3831d8c82c42789d.tar.xz linux-710da3c8ea7dfbd327920afd3831d8c82c42789d.zip |
sched/core: Prevent race condition between cpuset and __sched_setscheduler()
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.
Tested-by: Dietmar Eggemann <dietmar.eggemann@arm.com>
Signed-off-by: Juri Lelli <juri.lelli@redhat.com>
Signed-off-by: Peter Zijlstra (Intel) <peterz@infradead.org>
Cc: Linus Torvalds <torvalds@linux-foundation.org>
Cc: Peter Zijlstra <peterz@infradead.org>
Cc: Thomas Gleixner <tglx@linutronix.de>
Cc: bristot@redhat.com
Cc: claudio@evidence.eu.com
Cc: lizefan@huawei.com
Cc: longman@redhat.com
Cc: luca.abeni@santannapisa.it
Cc: mathieu.poirier@linaro.org
Cc: rostedt@goodmis.org
Cc: tj@kernel.org
Cc: tommaso.cucinotta@santannapisa.it
Link: https://lkml.kernel.org/r/20190719140000.31694-9-juri.lelli@redhat.com
Signed-off-by: Ingo Molnar <mingo@kernel.org>
Diffstat (limited to 'kernel/cgroup')
-rw-r--r-- | kernel/cgroup/cpuset.c | 11 |
1 files changed, 11 insertions, 0 deletions
diff --git a/kernel/cgroup/cpuset.c b/kernel/cgroup/cpuset.c index 5c5014caa23c..c52bc91f882b 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; |