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serial: amba-pl011: lock console writes against interrupts

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commit ef605fdb33 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 <rabin.vincent@stericsson.com>
Reviewed-by: Srinidhi Kasagar <srinidhi.kasagar@stericsson.com>
Reviewed-by: Bibek Basu <bibek.basu@stericsson.com>
Reviewed-by: Shreshtha Kumar Sahu <shreshthakumar.sahu@stericsson.com>
Signed-off-by: Linus Walleij <linus.walleij@linaro.org>
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>
This commit is contained in:
Rabin Vincent
2012-01-17 11:52:28 +01:00
committed by Greg Kroah-Hartman
parent 47f7a05bd0
commit f0661faa59
1 changed files with 14 additions and 0 deletions
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14
drivers/tty/serial/amba-pl011.c
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@@ -1733,9 +1733,19 @@ 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
*/
@@ -1755,6 +1765,10 @@ 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);
}