This is a note to let you know that I've just added the patch titled
serial_core.c: add put_device() after device_find_child()
to my tty git tree which can be found at
git://git.kernel.org/pub/scm/linux/kernel/git/gregkh/tty.git
in the tty-next branch.
The patch will show up in the next release of the linux-next tree
(usually sometime within the next 24 hours during the week.)
The patch will also be merged in the next major kernel release
during the merge window.
If you have any questions about this process, please let me know.
>From 5a65dcc04cda41f4122aacc37a5a348454645399 Mon Sep 17 00:00:00 2001
From: Federico Vaga <federico.vaga@xxxxxxxxx>
Date: Mon, 15 Apr 2013 16:01:07 +0200
Subject: serial_core.c: add put_device() after device_find_child()
The serial core uses device_find_child() but does not drop the reference to
the retrieved child after using it. This patch add the missing put_device().
What I have done to test this issue.
I used a machine with an AMBA PL011 serial driver. I tested the patch on
next-20120408 because the last branch [next-20120415] does not boot on this
board.
For test purpose, I added some pr_info() messages to print the refcount
after device_find_child() (lines: 1937,2009), and after put_device()
(lines: 1947, 2021).
Boot the machine *without* put_device(). Then:
echo reboot > /sys/power/disk
echo disk > /sys/power/state
[ 87.058575] uart_suspend_port:1937 refcount 4
[ 87.058582] uart_suspend_port:1947 refcount 4
[ 87.098083] uart_resume_port:2009refcount 5
[ 87.098088] uart_resume_port:2021 refcount 5
echo disk > /sys/power/state
[ 103.055574] uart_suspend_port:1937 refcount 6
[ 103.055580] uart_suspend_port:1947 refcount 6
[ 103.095322] uart_resume_port:2009 refcount 7
[ 103.095327] uart_resume_port:2021 refcount 7
echo disk > /sys/power/state
[ 252.459580] uart_suspend_port:1937 refcount 8
[ 252.459586] uart_suspend_port:1947 refcount 8
[ 252.499611] uart_resume_port:2009 refcount 9
[ 252.499616] uart_resume_port:2021 refcount 9
The refcount continuously increased.
Boot the machine *with* this patch. Then:
echo reboot > /sys/power/disk
echo disk > /sys/power/state
[ 159.333559] uart_suspend_port:1937 refcount 4
[ 159.333566] uart_suspend_port:1947 refcount 3
[ 159.372751] uart_resume_port:2009 refcount 4
[ 159.372755] uart_resume_port:2021 refcount 3
echo disk > /sys/power/state
[ 185.713614] uart_suspend_port:1937 refcount 4
[ 185.713621] uart_suspend_port:1947 refcount 3
[ 185.752935] uart_resume_port:2009 refcount 4
[ 185.752940] uart_resume_port:2021 refcount 3
echo disk > /sys/power/state
[ 207.458584] uart_suspend_port:1937 refcount 4
[ 207.458591] uart_suspend_port:1947 refcount 3
[ 207.498598] uart_resume_port:2009 refcount 4
[ 207.498605] uart_resume_port:2021 refcount 3
The refcount correctly handled.
Signed-off-by: Federico Vaga <federico.vaga@xxxxxxxxx>
Cc: stable <stable@xxxxxxxxxxxxxxx>
Signed-off-by: Greg Kroah-Hartman <gregkh@xxxxxxxxxxxxxxxxxxx>
---
drivers/tty/serial/serial_core.c | 4 ++++
1 file changed, 4 insertions(+)
diff --git a/drivers/tty/serial/serial_core.c b/drivers/tty/serial/serial_core.c
index a400002..8fbb6d2 100644
--- a/drivers/tty/serial/serial_core.c
+++ b/drivers/tty/serial/serial_core.c
@@ -1941,6 +1941,8 @@ int uart_suspend_port(struct uart_driver *drv, struct uart_port *uport)
mutex_unlock(&port->mutex);
return 0;
}
+ put_device(tty_dev);
+
if (console_suspend_enabled || !uart_console(uport))
uport->suspended = 1;
@@ -2006,9 +2008,11 @@ int uart_resume_port(struct uart_driver *drv, struct uart_port *uport)
disable_irq_wake(uport->irq);
uport->irq_wake = 0;
}
+ put_device(tty_dev);
mutex_unlock(&port->mutex);
return 0;
}
+ put_device(tty_dev);
uport->suspended = 0;
/*
--
1.8.2.1.368.g99c2266
--
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