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author | Schspa Shi <schspa@gmail.com> | 2022-08-28 20:03:02 +0300 |
---|---|---|
committer | Greg Kroah-Hartman <gregkh@linuxfoundation.org> | 2023-05-11 17:03:32 +0300 |
commit | 6472a6d0c79826256bfa3a6b45710dd499a984bf (patch) | |
tree | 53d961442a7512f325e13af0554440f755e11dc2 /drivers/clk | |
parent | 1969b143d09658e2e096e2252fcd594c8f8647b6 (diff) | |
download | linux-6472a6d0c79826256bfa3a6b45710dd499a984bf.tar.xz |
sched/rt: Fix bad task migration for rt tasks
[ Upstream commit feffe5bb274dd3442080ef0e4053746091878799 ]
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>
Signed-off-by: Sasha Levin <sashal@kernel.org>
Diffstat (limited to 'drivers/clk')
0 files changed, 0 insertions, 0 deletions