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| author |   TATSUKAWA KOSUKE (立川 江介) <tatsu-ab1@nec.com> | 2022-01-26 23:35:02 +0000 |
|---|---|---|
| committer |   Greg Kroah-Hartman <gregkh@linuxfoundation.org> | 2022-01-31 14:31:28 +0100 |
| commit | c816b2e65b0e86b95011418cad334f0524fc33b8 (patch) | |
| tree | d167dc27d2659fad2c2c92df172859f92ceb8096 /drivers/tty/n_tty.c | |
| parent | Linux 5.17-rc2 (diff) | |
| download | linux-dev-c816b2e65b0e86b95011418cad334f0524fc33b8.tar.xz linux-dev-c816b2e65b0e86b95011418cad334f0524fc33b8.zip | |
n_tty: wake up poll(POLLRDNORM) on receiving data
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/n_tty.c')
| -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 8933ef1f83c0..5e988e514653 100644 --- a/drivers/tty/n_tty.c +++ b/drivers/tty/n_tty.c @@ -1329,7 +1329,7 @@ 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, EPOLLIN); + wake_up_interruptible_poll(&tty->read_wait, EPOLLIN | EPOLLRDNORM); return; } } @@ -1561,7 +1561,7 @@ 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, EPOLLIN); + wake_up_interruptible_poll(&tty->read_wait, EPOLLIN | EPOLLRDNORM); } } |