Messages in this thread Patch in this message | | | Date | Wed, 01 Feb 2012 13:00:15 -0800 | From | Greg KH <> | Subject | [51/89] serial: amba-pl011: lock console writes against interrupts |
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3.2-stable review patch. If anyone has any objections, please let me know.
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From: Rabin Vincent <rabin.vincent@stericsson.com>
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 <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>
--- 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); }
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