Hi Peter,
Peter Hurley <peter@xxxxxxxxxxxxxxxxxx> writes:
> Hi Johannes,
>
> On 08/03/2015 09:58 AM, Johannes Thumshirn wrote:
>> Fix panic caused by a race between men_z135_intr() and men_z135_set_termios().
>>
>> men_z135_intr() and men_z135_set_termios() both hold the struct uart_port::lock
>> spinlock, but men_z135_intr() does a spin_lock_irqsave() and
>> men_z135_set_termios() does a normal spin_lock(), which can lead to a deadlock
>> when an interrupt is called while the lock is being helt by
>> men_z135_set_termios().
>
>
> The irq handler can and should use normal spin_lock()/unlock().
I always thought an irq handler _must_ use the irqsave versions. Good to
know that.
>
> The set_termios() method should used spin_lock_irq(); there's no need to save the
> interrupt state because that method will never be called from interrupt context.
>
> So the 'flags' local can be dropped from the patch.
Given that the irqsave variant isn't needed that sounds reasonable.
>
> Also, the port lock is already initialized in uart_add_one_port() and should
> not be initialized by the probe() function.
OK, do you prefer (or better Greg and Jiri) prefer that change folded
into this patch or an extra patch?
>
> Regards,
> Peter Hurley
>
>> This was discovered using a insmod, hardware looppback send/receive, rmmod
>> stress test.
>>
>> Signed-off-by: Johannes Thumshirn <jthumshirn@xxxxxxx>
>> Cc: Andreas Werner <andreas.werner@xxxxxx>
>> ---
>> drivers/tty/serial/men_z135_uart.c | 5 +++--
>> 1 file changed, 3 insertions(+), 2 deletions(-)
>>
>> diff --git a/drivers/tty/serial/men_z135_uart.c b/drivers/tty/serial/men_z135_uart.c
>> index 35c5550..d020435 100644
>> --- a/drivers/tty/serial/men_z135_uart.c
>> +++ b/drivers/tty/serial/men_z135_uart.c
>> @@ -656,6 +656,7 @@ static void men_z135_set_termios(struct uart_port *port,
>> struct ktermios *old)
>> {
>> struct men_z135_port *uart = to_men_z135(port);
>> + unsigned long flags;
>> unsigned int baud;
>> u32 conf_reg;
>> u32 bd_reg;
>> @@ -717,7 +718,7 @@ static void men_z135_set_termios(struct uart_port *port,
>>
>> baud = uart_get_baud_rate(port, termios, old, 0, uart_freq / 16);
>>
>> - spin_lock(&port->lock);
>> + spin_lock_irqsave(&port->lock, flags);
>> if (tty_termios_baud_rate(termios))
>> tty_termios_encode_baud_rate(termios, baud, baud);
>>
>> @@ -725,7 +726,7 @@ static void men_z135_set_termios(struct uart_port *port,
>> iowrite32(bd_reg, port->membase + MEN_Z135_BAUD_REG);
>>
>> uart_update_timeout(port, termios->c_cflag, baud);
>> - spin_unlock(&port->lock);
>> + spin_unlock_irqrestore(&port->lock, flags);
>> }
>>
>> static const char *men_z135_type(struct uart_port *port)
>>
>
--
Johannes Thumshirn Storage
jthumshirn@xxxxxxx +49 911 74053 689
SUSE LINUX GmbH, Maxfeldstr. 5, 90409 Nürnberg
GF: F. Imendörffer, J. Smithard, J. Guild, D. Upmanyu, G. Norton
HRB 21284 (AG Nürnberg)
Key fingerprint = EC38 9CAB C2C4 F25D 8600 D0D0 0393 969D 2D76 0850
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