This is a note to let you know that I've just added the patch titled
serial: amba-pl011: lock console writes against interrupts
to the 3.2-stable tree which can be found at:
http://www.kernel.org/git/?p=linux/kernel/git/stable/stable-queue.git;a=summary
The filename of the patch is:
serial-amba-pl011-lock-console-writes-against-interrupts.patch
and it can be found in the queue-3.2 subdirectory.
If you, or anyone else, feels it should not be added to the stable tree,
please let <[email protected]> know about it.
>From ef605fdb33883d687cff5ba75095a91b313b4966 Mon Sep 17 00:00:00 2001
From: Rabin Vincent <[email protected]>
Date: Tue, 17 Jan 2012 11:52:28 +0100
Subject: serial: amba-pl011: lock console writes against interrupts
From: Rabin Vincent <[email protected]>
commit ef605fdb33883d687cff5ba75095a91b313b4966 upstream.
Protect against pl011_console_write() and the interrupt for
the console UART running concurrently on different CPUs.
Otherwise the console_write could spin for a long time
waiting for the UART to become not busy, while the other
CPU continuously services UART interrupts and keeps the
UART busy.
The checks for sysrq and oops_in_progress are taken
from 8250.c.
Signed-off-by: Rabin Vincent <[email protected]>
Reviewed-by: Srinidhi Kasagar <[email protected]>
Reviewed-by: Bibek Basu <[email protected]>
Reviewed-by: Shreshtha Kumar Sahu <[email protected]>
Signed-off-by: Linus Walleij <[email protected]>
Signed-off-by: Greg Kroah-Hartman <[email protected]>
---
drivers/tty/serial/amba-pl011.c | 14 ++++++++++++++
1 file changed, 14 insertions(+)
--- a/drivers/tty/serial/amba-pl011.c
+++ b/drivers/tty/serial/amba-pl011.c
@@ -1740,9 +1740,19 @@ pl011_console_write(struct console *co,
{
struct uart_amba_port *uap = amba_ports[co->index];
unsigned int status, old_cr, new_cr;
+ unsigned long flags;
+ int locked = 1;
clk_enable(uap->clk);
+ local_irq_save(flags);
+ if (uap->port.sysrq)
+ locked = 0;
+ else if (oops_in_progress)
+ locked = spin_trylock(&uap->port.lock);
+ else
+ spin_lock(&uap->port.lock);
+
/*
* First save the CR then disable the interrupts
*/
@@ -1762,6 +1772,10 @@ pl011_console_write(struct console *co,
} while (status & UART01x_FR_BUSY);
writew(old_cr, uap->port.membase + UART011_CR);
+ if (locked)
+ spin_unlock(&uap->port.lock);
+ local_irq_restore(flags);
+
clk_disable(uap->clk);
}
Patches currently in stable-queue which might be from
[email protected] are
queue-3.2/serial-amba-pl011-lock-console-writes-against-interrupts.patch
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