Re: [PATCH] sound: fix hang in mpu401_uart.c

[Takashi Iwai <tiwai@suse.de>]

At Sun, 16 Apr 2006 04:12:36 +0100,
Jon Masters wrote:
> 
> From: Jon Masters <jcm@jonmasters.org>
> 
> This fixes a hang in mpu401_uart.c that can occur when the mpu401
> interface is non-existent or otherwise doesn't respond to commands but
> we issue IO anyway. snd_mpu401_uart_cmd now returns an error code that is
> passed up the stack so that an open() will fail immediately in such cases.
> 
> Eventually discovered after wine/cxoffice would constantly cause hard
> lockups on my desktop immediately after loading (emulating Windows too
> well). Turned out that I'd recently moved my sound cards around and
> using /dev/sequencer now talks to a sound card with a broken MPU.
> 
> Signed-off-by: Jon Masters <jcm@jonmasters.org>
(snip)
> @@ -235,8 +238,12 @@
>  	if (mpu->open_input && (err = mpu->open_input(mpu)) < 0)
>  		return err;
>  	if (! test_bit(MPU401_MODE_BIT_OUTPUT, &mpu->mode)) {
> -		snd_mpu401_uart_cmd(mpu, MPU401_RESET, 1);
> -		snd_mpu401_uart_cmd(mpu, MPU401_ENTER_UART, 1);
> +		if ((err = snd_mpu401_uart_cmd(mpu, MPU401_RESET, 1))) {
> +			return -EFAULT;

IMO, -EFAULT isn't a good choice for this kind of error.

> @@ -252,8 +259,10 @@
>  	if (mpu->open_output && (err = mpu->open_output(mpu)) < 0)
>  		return err;
>  	if (! test_bit(MPU401_MODE_BIT_INPUT, &mpu->mode)) {
> -		snd_mpu401_uart_cmd(mpu, MPU401_RESET, 1);
> -		snd_mpu401_uart_cmd(mpu, MPU401_ENTER_UART, 1);
> +		if ((err = snd_mpu401_uart_cmd(mpu, MPU401_RESET, 1)))
> +			return -EFAULT;
> +		if ((err = snd_mpu401_uart_cmd(mpu, MPU401_ENTER_UART, 1)))
> +			return -EFAULT;

Missing close in the error path?


Takashi