sched: Remove need_migrate_task() (bd8e7dde) · Commits · 戴 / test

Oleg noticed that need_migrate_task() doesn't need the ->on_cpu check now that ttwu() doesn't do remote enqueues for !->on_rq && ->on_cpu, so remove the helper and replace the single instance with a direct ->on_rq test. Suggested-by:

Oleg Nesterov <oleg@redhat.com> Reviewed-by:

Frank Rowand <frank.rowand@am.sony.com> Signed-off-by:

Peter Zijlstra <a.p.zijlstra@chello.nl> Cc: Mike Galbraith <efault@gmx.de> Cc: Nick Piggin <npiggin@kernel.dk> Cc: Linus Torvalds <torvalds@linux-foundation.org> Cc: Andrew Morton <akpm@linux-foundation.org> Link: http://lkml.kernel.org/r/20110405152729.556674812@chello.nl Signed-off-by:

Ingo Molnar <mingo@elte.hu>

kernel/sched.c

+1 −16

Original line number	Diff line number	Diff line
		@@ -2198,21 +2198,6 @@ struct migration_arg {

		static int migration_cpu_stop(void *data);

		/*
		* The task's runqueue lock must be held.
		* Returns true if you have to wait for migration thread.
		*/
		static bool need_migrate_task(struct task_struct *p)
		{
		/*
		* If the task is not on a runqueue (and not running), then
		* the next wake-up will properly place the task.
		*/
		bool running = p->on_rq \|\| p->on_cpu;
		smp_rmb(); /* finish_lock_switch() */
		return running;
		}

		/*
		* wait_task_inactive - wait for a thread to unschedule.
		*
		@@ -5985,7 +5970,7 @@ int set_cpus_allowed_ptr(struct task_struct p, const struct cpumask new_mask)
		goto out;

		dest_cpu = cpumask_any_and(cpu_active_mask, new_mask);
		if (need_migrate_task(p)) {
		if (p->on_rq) {
		struct migration_arg arg = { p, dest_cpu };
		/* Need help from migration thread: drop lock and wait. */
		task_rq_unlock(rq, p, &flags);

Admin message