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authorJohan Hovold <johan@kernel.org>2021-04-21 11:54:50 +0200
committerGreg Kroah-Hartman <gregkh@linuxfoundation.org>2021-04-22 12:09:25 +0200
commit80d43febacf1502bb562e58d8ab76ecee2655a8b (patch)
tree29042bc8d379e5a625bd6ba35e2322d5343508ba
parentd0aa2820b9e85e79f5a76eb7874316aaa04bdff9 (diff)
downloadlinux-80d43febacf1502bb562e58d8ab76ecee2655a8b.tar.bz2
serial: ar933x: drop low-latency workaround
Commit b16c8e3eed12 ("tty: serial: ar933x: 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> Link: https://lore.kernel.org/r/20210421095509.3024-8-johan@kernel.org Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>
-rw-r--r--drivers/tty/serial/ar933x_uart.c2
1 files changed, 0 insertions, 2 deletions
diff --git a/drivers/tty/serial/ar933x_uart.c b/drivers/tty/serial/ar933x_uart.c
index c2be7cf91399..4379ca4842ae 100644
--- a/drivers/tty/serial/ar933x_uart.c
+++ b/drivers/tty/serial/ar933x_uart.c
@@ -385,9 +385,7 @@ static void ar933x_uart_rx_chars(struct ar933x_uart_port *up)
tty_insert_flip_char(port, ch, TTY_NORMAL);
} while (max_count-- > 0);
- spin_unlock(&up->port.lock);
tty_flip_buffer_push(port);
- spin_lock(&up->port.lock);
}
static void ar933x_uart_tx_chars(struct ar933x_uart_port *up)