Re: [PATCH] little schedule() cleanup: use cached current value

From: Ingo Molnar
Date: Tue Nov 09 2004 - 06:46:10 EST

* Oleg Nesterov <oleg@xxxxxxxxxx> wrote:

> @@ -2636,7 +2636,7 @@ switch_tasks:
> } else
> spin_unlock_irq(&rq->lock);
> - reacquire_kernel_lock(current);
> + reacquire_kernel_lock(next);
> preempt_enable_no_resched();
> if (unlikely(test_thread_flag(TIF_NEED_RESCHED)))
> goto need_resched;

nack. We switch the kernel stack in switch_to() so 'next' here is the
old task we switched to before we went off the CPU. The value of 'next'
doesnt get carried over a context-switch. (we do carry 'prev' over via
assembly trickery because we need it, but not 'next'.) This change would
most likely result in rare, hard-to-track-down BKL-related crashes all
around the place.

the other bits are OK, please resend them.

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