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| author | TATSUKAWA KOSUKE (立川 江介) <tatsu-ab1@nec.com> | 2022-01-27 02:35:02 +0300 |
|---|---|---|
| committer | Greg Kroah-Hartman <gregkh@linuxfoundation.org> | 2022-02-16 14:44:51 +0300 |
| commit | d8c9812aa2a70eac1dcb468b13057dd37a204005 (patch) | |
| tree | 7ec81cef4c466ef5973a4af778aa2f7747be2629 | |
| parent | 0020d740dd05e4db1076bef128eca46a5da0a2bb (diff) | |
| download | linux-d8c9812aa2a70eac1dcb468b13057dd37a204005.tar.xz | |
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>
| -rw-r--r-- | drivers/tty/n_tty.c | 4 |
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); } } |