Re: Linux 2.2.19pre2

From: Andrea Arcangeli (andrea@suse.de)
Date: Fri Dec 22 2000 - 08:19:29 EST


On Fri, Dec 22, 2000 at 06:33:00PM +1100, Andrew Morton wrote:
> add_waitqueue_exclusive() and TASK_EXCLUSIVE, add a

There's no add_waitqueue_exclusive in my patch.

> Except for this bit, which looks slightly fatal:
>
> /*
> * We can drop the read-lock early if this
> * is the only/last process.
> */
> if (next == head) {
> read_unlock(&waitqueue_lock);
> wake_up_process(p);
> goto out;
> }
>
> Once the waitqueue_lock has been dropped, the task at `p'
> is free to remove itself from the waitqueue and exit. This
> CPU can then try to wake up a non-existent task, no?

Yes, that was an unlikely-to-happen SMP race I inerith from 2.2.18 and all
previous 2.2.x vanilla kernels. Thanks.

Andrea
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