sched: normalize_rt_tasks(): Don't use _irqsave for tasklist_lock, use task_rq_lock()
sched: normalize_rt_tasks(): Don't use _irqsave for tasklist_lock, use task_rq_lock()

1. read_lock(tasklist_lock) does not need to disable irqs.

2. ->mm != NULL is a common mistake, use PF_KTHREAD.

3. The second ->mm check can be simply removed.

4. task_rq_lock() looks better than raw_spin_lock(&p->pi_lock) +
   __task_rq_lock().

Signed-off-by: Oleg Nesterov <20b70f0af00562e63758b9ee42012ecc96c58590@redhat.com>
Signed-off-by: Peter Zijlstra (Intel) <3fddac958924aef220f202ca567388ddab3f14a8@infradead.org>
Cc: Kirill Tkhai <f0a29e10abf52e3965939db20f961ffd5c7f3d14@yandex.ru>
Cc: Mike Galbraith <d1e2fad1f6337a0a3a08db0a5375a8a96150db4c@gmail.com>
Cc: Linus Torvalds <69652caca27c8b940640ad396ab71f93cacec34f@linux-foundation.org>
Link: bcf73d2ec49b4c6d7e8b5e9f4479ffca2b34918a@redhat.com
Signed-off-by: Ingo Molnar <9dbbbf0688fedc85ad4da37637f1a64b8c718ee2@kernel.org>

KristFoundation/Programs,KristFoundation/Programs,KristFoundation/Programs,KristFoundation/Programs,KristFoundation/Programs,KristFoundation/Programs