diff options
author | Juri Lelli <juri.lelli@redhat.com> | 2019-07-19 17:00:00 +0300 |
---|---|---|
committer | Ingo Molnar <mingo@kernel.org> | 2019-07-25 16:55:04 +0300 |
commit | 710da3c8ea7dfbd327920afd3831d8c82c42789d (patch) | |
tree | 146d69299e74b9c9fe0e23a0588484543ccec8f1 /kernel/sched/core.c | |
parent | 1a763fd7c6335e3122c1cc09576ef6c99ada4267 (diff) | |
download | linux-710da3c8ea7dfbd327920afd3831d8c82c42789d.tar.xz |
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/sched/core.c')
-rw-r--r-- | kernel/sched/core.c | 20 |
1 files changed, 17 insertions, 3 deletions
diff --git a/kernel/sched/core.c b/kernel/sched/core.c index 1af3d2dc6b29..1bceb22dac18 100644 --- a/kernel/sched/core.c +++ b/kernel/sched/core.c @@ -4698,6 +4698,9 @@ recheck: return retval; } + if (pi) + cpuset_read_lock(); + /* * Make sure no PI-waiters arrive (or leave) while we are * changing the priority of the task: @@ -4772,6 +4775,8 @@ change: if (unlikely(oldpolicy != -1 && oldpolicy != p->policy)) { policy = oldpolicy = -1; task_rq_unlock(rq, p, &rf); + if (pi) + cpuset_read_unlock(); goto recheck; } @@ -4832,8 +4837,10 @@ change: 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); @@ -4843,6 +4850,8 @@ change: unlock: task_rq_unlock(rq, p, &rf); + if (pi) + cpuset_read_unlock(); return retval; } @@ -4927,10 +4936,15 @@ 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 (likely(p)) + get_task_struct(p); rcu_read_unlock(); + if (likely(p)) { + retval = sched_setscheduler(p, policy, &lparam); + put_task_struct(p); + } + return retval; } |