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Commit ef605fdb authored by Rabin Vincent's avatar Rabin Vincent Committed by Greg Kroah-Hartman
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serial: amba-pl011: lock console writes against interrupts 



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.

Cc: stable <stable@vger.kernel.org>
Signed-off-by: default avatarRabin Vincent <rabin.vincent@stericsson.com>
Reviewed-by: default avatarSrinidhi Kasagar <srinidhi.kasagar@stericsson.com>
Reviewed-by: default avatarBibek Basu <bibek.basu@stericsson.com>
Reviewed-by: default avatarShreshtha Kumar Sahu <shreshthakumar.sahu@stericsson.com>
Signed-off-by: default avatarLinus Walleij <linus.walleij@linaro.org>
Signed-off-by: default avatarGreg Kroah-Hartman <gregkh@suse.de>
parent d8d8ffa4

drivers/tty/serial/amba-pl011.c

+14 −0
Original line number Diff line number Diff line
@@ -1751,9 +1751,19 @@ pl011_console_write(struct console *co, const char *s, unsigned int count) 
{

	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

	 */
@@ -1773,6 +1783,10 @@ pl011_console_write(struct console *co, const char *s, unsigned int count) 
	} 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);

}