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authorTATSUKAWA KOSUKE (立川 江介) <tatsu-ab1@nec.com>2022-01-26 23:35:02 +0000
committerGreg Kroah-Hartman <gregkh@linuxfoundation.org>2022-02-16 12:44:51 +0100
commitd8c9812aa2a70eac1dcb468b13057dd37a204005 (patch)
tree7ec81cef4c466ef5973a4af778aa2f7747be2629 /drivers/tty
parent0020d740dd05e4db1076bef128eca46a5da0a2bb (diff)
downloadlinux-rt-d8c9812aa2a70eac1dcb468b13057dd37a204005.tar.gz
n_tty: wake up poll(POLLRDNORM) on receiving data
commit c816b2e65b0e86b95011418cad334f0524fc33b8 upstream. The poll man page says POLLRDNORM is equivalent to POLLIN when used as an event. $ man poll <snip> POLLRDNORM Equivalent to POLLIN. However, in n_tty driver, POLLRDNORM does not return until timeout even if there is terminal input, whereas POLLIN returns. The following test program works until kernel-3.17, but the test stops in poll() after commit 57087d515441 ("tty: Fix spurious poll() wakeups"). [Steps to run test program] $ cc -o test-pollrdnorm test-pollrdnorm.c $ ./test-pollrdnorm foo <-- Type in something from the terminal followed by [RET]. The string should be echoed back. ------------------------< test-pollrdnorm.c >------------------------ #include <stdio.h> #include <errno.h> #include <poll.h> #include <unistd.h> void main(void) { int n; unsigned char buf[8]; struct pollfd fds[1] = {{ 0, POLLRDNORM, 0 }}; n = poll(fds, 1, -1); if (n < 0) perror("poll"); n = read(0, buf, 8); if (n < 0) perror("read"); if (n > 0) write(1, buf, n); } ------------------------------------------------------------------------ The attached patch fixes this problem. Many calls to wake_up_interruptible_poll() in the kernel source code already specify "POLLIN | POLLRDNORM". Fixes: 57087d515441 ("tty: Fix spurious poll() wakeups") Cc: stable@vger.kernel.org Signed-off-by: Kosuke Tatsukawa <tatsu-ab1@nec.com> Link: https://lore.kernel.org/r/TYCPR01MB81901C0F932203D30E452B3EA5209@TYCPR01MB8190.jpnprd01.prod.outlook.com Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>
Diffstat (limited to 'drivers/tty')
-rw-r--r--drivers/tty/n_tty.c4
1 files changed, 2 insertions, 2 deletions
diff --git a/drivers/tty/n_tty.c b/drivers/tty/n_tty.c
index 8214b0326b3a..690cb5a63f9a 100644
--- a/drivers/tty/n_tty.c
+++ b/drivers/tty/n_tty.c
@@ -1377,7 +1377,7 @@ handle_newline:
put_tty_queue(c, ldata);
smp_store_release(&ldata->canon_head, ldata->read_head);
kill_fasync(&tty->fasync, SIGIO, POLL_IN);
- wake_up_interruptible_poll(&tty->read_wait, POLLIN);
+ wake_up_interruptible_poll(&tty->read_wait, POLLIN | POLLRDNORM);
return 0;
}
}
@@ -1658,7 +1658,7 @@ static void __receive_buf(struct tty_struct *tty, const unsigned char *cp,
if (read_cnt(ldata)) {
kill_fasync(&tty->fasync, SIGIO, POLL_IN);
- wake_up_interruptible_poll(&tty->read_wait, POLLIN);
+ wake_up_interruptible_poll(&tty->read_wait, POLLIN | POLLRDNORM);
}
}