From: Johan Hovold <johan@kernel.org>
To: Greg Kroah-Hartman <gregkh@linuxfoundation.org>
Cc: Jiri Slaby <jirislaby@kernel.org>,
linux-serial@vger.kernel.org, linux-kernel@vger.kernel.org,
Johan Hovold <johan@kernel.org>
Subject: [PATCH 06/26] serial: apbuart: drop low-latency workaround
Date: Wed, 21 Apr 2021 11:54:49 +0200 [thread overview]
Message-ID: <20210421095509.3024-7-johan@kernel.org> (raw)
In-Reply-To: <20210421095509.3024-1-johan@kernel.org>
Commit 78d34d75c84d ("tty: serial: apbuart: drop uart_port->lock before
calling tty_flip_buffer_push()") claimed to address a locking
issue but only provided a dubious lockdep splat from an unrelated
driver, which in the end turned out to be due a broken local change
carried by the author.
Unfortunately these patches were merged before the issue had been
analysed properly so the commit messages makes no sense whatsoever.
The real issue was first seen on RT which at the time effectively always
set the low_latency flag for all serial drivers by patching
tty_flip_buffer_push(). This in turn revealed that many drivers did not
handle the infamous low_latency behaviour which meant that data was
pushed immediately to the line discipline instead of being deferred to a
work queue.
Since commit a9c3f68f3cd8 ("tty: Fix low_latency BUG"),
tty_flip_buffer_push() always schedules a work item to push data to the
line discipline and there's no need to keep any low_latency hacks
around.
Link: https://lore.kernel.org/linux-serial/cover.1376923198.git.viresh.kumar@linaro.org/
Signed-off-by: Johan Hovold <johan@kernel.org>
---
drivers/tty/serial/apbuart.c | 2 --
1 file changed, 2 deletions(-)
diff --git a/drivers/tty/serial/apbuart.c b/drivers/tty/serial/apbuart.c
index e8d56e899ec7..d8c937bdf3f9 100644
--- a/drivers/tty/serial/apbuart.c
+++ b/drivers/tty/serial/apbuart.c
@@ -117,9 +117,7 @@ static void apbuart_rx_chars(struct uart_port *port)
status = UART_GET_STATUS(port);
}
- spin_unlock(&port->lock);
tty_flip_buffer_push(&port->state->port);
- spin_lock(&port->lock);
}
static void apbuart_tx_chars(struct uart_port *port)
--
2.26.3
next prev parent reply other threads:[~2021-04-21 9:56 UTC|newest]
Thread overview: 34+ messages / expand[flat|nested] mbox.gz Atom feed top
2021-04-21 9:54 [PATCH 00/26] tty: drop low-latency workarounds Johan Hovold
2021-04-21 9:54 ` [PATCH 01/26] tty: mxser: drop low-latency workaround Johan Hovold
2021-04-22 5:59 ` Jiri Slaby
2021-04-21 9:54 ` [PATCH 02/26] serial: altera_jtaguart: " Johan Hovold
2021-04-21 10:03 ` Tobias Klauser
2021-04-21 9:54 ` [PATCH 03/26] serial: altera_uart: " Johan Hovold
2021-04-21 10:03 ` Tobias Klauser
2021-04-21 9:54 ` [PATCH 04/26] serial: amba-pl010: " Johan Hovold
2021-04-21 9:54 ` [PATCH 05/26] serial: amba-pl011: " Johan Hovold
2021-04-22 0:18 ` Linus Walleij
2021-04-21 9:54 ` Johan Hovold [this message]
2021-04-21 9:54 ` [PATCH 07/26] serial: ar933x: " Johan Hovold
2021-04-21 9:54 ` [PATCH 08/26] serial: arc_uart: " Johan Hovold
2021-04-21 9:54 ` [PATCH 09/26] serial: atmel_serial: " Johan Hovold
2021-04-21 9:54 ` [PATCH 10/26] serial: bcm63xx: " Johan Hovold
2021-04-21 9:54 ` [PATCH 11/26] serial: icom: " Johan Hovold
2021-04-21 9:54 ` [PATCH 12/26] serial: lpc32xx_hs: " Johan Hovold
2021-04-21 9:54 ` [PATCH 13/26] serial: mcf: " Johan Hovold
2021-04-21 9:54 ` [PATCH 14/26] serial: meson: " Johan Hovold
2021-04-21 9:54 ` [PATCH 15/26] serial: mpc52xx_uart: " Johan Hovold
2021-04-21 9:54 ` [PATCH 16/26] serial: msm_serial: " Johan Hovold
2021-04-21 17:44 ` Bjorn Andersson
2021-04-21 9:55 ` [PATCH 17/26] serial: owl: " Johan Hovold
2021-04-21 9:55 ` [PATCH 18/26] serial: rda: " Johan Hovold
2021-04-21 9:55 ` [PATCH 19/26] serial: rp2: " Johan Hovold
2021-04-21 9:55 ` [PATCH 20/26] serial: sa1100: " Johan Hovold
2021-04-21 9:55 ` [PATCH 21/26] serial: txx9: " Johan Hovold
2021-04-21 9:55 ` [PATCH 22/26] serial: sifive: " Johan Hovold
2021-04-21 9:55 ` [PATCH 23/26] serial: sunsu: " Johan Hovold
2021-04-21 16:56 ` David Miller
2021-04-21 9:55 ` [PATCH 24/26] serial: timbuart: " Johan Hovold
2021-04-21 9:55 ` [PATCH 25/26] serial: vt8500: " Johan Hovold
2021-04-21 9:55 ` [PATCH 26/26] serial: xilinx_uartps: " Johan Hovold
2021-04-22 10:09 ` [PATCH 00/26] tty: drop low-latency workarounds Greg Kroah-Hartman
Reply instructions:
You may reply publicly to this message via plain-text email
using any one of the following methods:
* Save the following mbox file, import it into your mail client,
and reply-to-all from there: mbox
Avoid top-posting and favor interleaved quoting:
https://en.wikipedia.org/wiki/Posting_style#Interleaved_style
* Reply using the --to, --cc, and --in-reply-to
switches of git-send-email(1):
git send-email \
--in-reply-to=20210421095509.3024-7-johan@kernel.org \
--to=johan@kernel.org \
--cc=gregkh@linuxfoundation.org \
--cc=jirislaby@kernel.org \
--cc=linux-kernel@vger.kernel.org \
--cc=linux-serial@vger.kernel.org \
/path/to/YOUR_REPLY
https://kernel.org/pub/software/scm/git/docs/git-send-email.html
* If your mail client supports setting the In-Reply-To header
via mailto: links, try the mailto: link
Be sure your reply has a Subject: header at the top and a blank line
before the message body.
This is a public inbox, see mirroring instructions
for how to clone and mirror all data and code used for this inbox;
as well as URLs for NNTP newsgroup(s).