Hi Eli,
The problem is normal_poll in drivers/char/n_tty.c:
> if (tty->driver->chars_in_buffer(tty) < WAKEUP_CHARS)
> mask |= POLLOUT | POLLWRNORM;
It assumes that a following write will succeed if less than 256 bytes
are in the write buffer right now. This assumption is wrong for
con_write_room: if the console is stopped, it returns 0 bytes buffer
size (con_write_room()). Dito for pty_write_room.
The attached patch fixes your test case, but I don't understand tty
devices good enough to guarantee anything.
--
Manfred
--- 2.5/drivers/char/n_tty.c 2003-07-05 09:13:01.000000000 +0200 +++ build-2.5/drivers/char/n_tty.c 2003-07-27 20:44:58.000000000 +0200 @@ -1251,7 +1251,8 @@ else tty->minimum_to_wake = 1; } - if (tty->driver->chars_in_buffer(tty) < WAKEUP_CHARS) + if (tty->driver->chars_in_buffer(tty) < WAKEUP_CHARS && + tty->driver->write_room(tty) > 0) mask |= POLLOUT | POLLWRNORM; return mask; }
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This archive was generated by hypermail 2b29 : Thu Jul 31 2003 - 22:00:34 EST