Re: [PATCH] pcmcia/pccard deadlock fix

[Andrew Morton <akpm@linux-foundation.org>]

> On Tue, 20 Feb 2007 16:08:11 +0100 "Markus Rechberger" <markus.rechberger@amd.com> wrote:
> following patch prevents a mutex/semaphore deadlock within the pcmcia
> framework when ejecting devices multiple times using pccardctl eject.
> 
> For some more details see:
> http://lkml.org/lkml/2007/2/19/58
> 
> --- a/drivers/pcmcia/cs.c
> +++ b/drivers/pcmcia/cs.c
> @@ -856,7 +856,8 @@ int pcmcia_eject_card(struct pcmcia_socket *skt)
>      
>  	cs_dbg(skt, 1, "user eject request\n");
>  
> -	mutex_lock(&skt->skt_mutex);
> +	if (!mutex_trylock(&skt->skt_mutex)) 
> +		return -EAGAIN;
>  	do {
>  		if (!(skt->state & SOCKET_PRESENT)) {
>  			ret = -ENODEV;
> index 18e111e..b9d3440 100644
> --- a/drivers/pcmcia/ds.c
> +++ b/drivers/pcmcia/ds.c
> @@ -1100,7 +1100,9 @@ static ssize_t pcmcia_store_allow_func_id_match(struct device *dev,
>  	if (!count)
>  		return -EINVAL;
>  
> -	mutex_lock(&p_dev->socket->skt_mutex);
> +	if (!mutex_trylock(&p_dev->socket->skt_mutex)) 
> +		return -EAGAIN;
> +
>  	p_dev->allow_func_id_match = 1;
>  	mutex_unlock(&p_dev->socket->skt_mutex);

That looks rather hacky.  I'll queue it up to bug Dominik with, but
hopeully we'll come up with some fix which avoids the trylocks.