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authorSchspa Shi <schspa@gmail.com>2022-08-28 19:03:02 +0200
committerPeter Zijlstra <peterz@infradead.org>2023-04-21 13:24:21 +0200
commitfeffe5bb274dd3442080ef0e4053746091878799 (patch)
tree0e69d00d399b44cc97094d2828d993fe6282fe22 /kernel/sched/deadline.c
parentsched: Fix performance regression introduced by mm_cid (diff)
downloadlinux-feffe5bb274dd3442080ef0e4053746091878799.tar.xz
linux-feffe5bb274dd3442080ef0e4053746091878799.zip
sched/rt: Fix bad task migration for rt tasks
Commit 95158a89dd50 ("sched,rt: Use the full cpumask for balancing") allows find_lock_lowest_rq() to pick a task with migration disabled. The purpose of the commit is to push the current running task on the CPU that has the migrate_disable() task away. However, there is a race which allows a migrate_disable() task to be migrated. Consider: CPU0 CPU1 push_rt_task check is_migration_disabled(next_task) task not running and migration_disabled == 0 find_lock_lowest_rq(next_task, rq); _double_lock_balance(this_rq, busiest); raw_spin_rq_unlock(this_rq); double_rq_lock(this_rq, busiest); <<wait for busiest rq>> <wakeup> task become running migrate_disable(); <context out> deactivate_task(rq, next_task, 0); set_task_cpu(next_task, lowest_rq->cpu); WARN_ON_ONCE(is_migration_disabled(p)); Fixes: 95158a89dd50 ("sched,rt: Use the full cpumask for balancing") Signed-off-by: Schspa Shi <schspa@gmail.com> Signed-off-by: Peter Zijlstra (Intel) <peterz@infradead.org> Reviewed-by: Steven Rostedt (Google) <rostedt@goodmis.org> Reviewed-by: Dietmar Eggemann <dietmar.eggemann@arm.com> Reviewed-by: Valentin Schneider <vschneid@redhat.com> Tested-by: Dwaine Gonyier <dgonyier@redhat.com>
Diffstat (limited to 'kernel/sched/deadline.c')
-rw-r--r--kernel/sched/deadline.c1
1 files changed, 1 insertions, 0 deletions
diff --git a/kernel/sched/deadline.c b/kernel/sched/deadline.c
index 4cc7e1ca066d..5a9a4b81c972 100644
--- a/kernel/sched/deadline.c
+++ b/kernel/sched/deadline.c
@@ -2246,6 +2246,7 @@ static struct rq *find_lock_later_rq(struct task_struct *task, struct rq *rq)
!cpumask_test_cpu(later_rq->cpu, &task->cpus_mask) ||
task_on_cpu(rq, task) ||
!dl_task(task) ||
+ is_migration_disabled(task) ||
!task_on_rq_queued(task))) {
double_unlock_balance(rq, later_rq);
later_rq = NULL;