Messages in this thread | | | Date | Mon, 07 Nov 2011 17:44:38 +0400 | From | Ilya Zykov <> | Subject | Re: PROBLEM: Race condition in tty buffer's function flush_to_ldisc(). |
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Alan Cox wrote:
> >> 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. > > It is single threaded with respect to itself (you can't have two > flush_to_ldisc on the same tty at once) but you can have a parallel > call to tty_buffer_flush. The tty_buffer_flush path needs to pick the > right approach reliably. >
Of course I know about tty_buffer_flush(), it only read TTY_FLUSHING, it can't change TTY_FLUSHING, if flush_to_ldisc() single threaded, we can change TTY_FLUSHING only in one place in one time(in flush_to_ldisc()), therefor we can use only "set_bit(TTY_FLUSHING, &tty->flags)" without test.
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