Re: PROBLEM: Race condition in tty buffer's function flush_to_ldisc().

[Ilya Zykov]

Alan Cox wrote:

> On Mon, 07 Nov 2011 15:14:34 +0400
> Ilya Zykov <ilya@xxxxxxx> wrote:
> 
>> Function flush_to_ldisc() call disc->ops->receive_buf(),
>> without tty->buf.lock and with TTY_FLUSHING bit set.
> 
> flush_to_ldisc is single threaded for a given tty. If you fail to
> ensure that is the case everything breaks.


Why we need: "if (!test_and_set_bit(TTY_FLUSHING, &tty->flags)) {"
if flush_to_ldisc is single threaded?
we can: set_bit(TTY_FLUSHING, &tty->flags)
without if() at all.

> 
> What cases does this occur ?
> 
> Also for the other patches do you have benchmarks yet ?
> 
> Alan
> 


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