index ac00424..c02bf0d 100644
--- 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);
> On Tue, 20 Feb 2007 16:08:11 +0100 "Markus Rechberger" <[email protected]> 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.
> On Tue, 20 Feb 2007 16:08:11 +0100
20 Feb was a long time ago, sorry. I was hoping to feed the pcmcia patches
through Dominik but I think he's busy with exams or such. So I get to
pretend to be pcmcia maintainer.
"Markus Rechberger" <[email protected]> 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
>
> Signed-off-by: Markus Rechberger <[email protected]>
>
> --
> Markus Rechberger
> Operating System Research Center
> AMD Saxony LLC & Co. KG
>
>
>
> [pcmcia-pccard-deadlock-fix.diff text/plain (757B)]
> index ac00424..c02bf0d 100644
> --- 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);
>
This is a pretty sad-looking solution. Does it not mean that sometimes
user-initiated actions will mysteriously fail?
Are you able to provide a more detailed description of why/how the deadlock
actually occurs so that perhaps a more robust fix can be implemented?
Thanks.
Andrew Morton wrote:
>> On Tue, 20 Feb 2007 16:08:11 +0100
>>
>
> 20 Feb was a long time ago, sorry. I was hoping to feed the pcmcia patches
> through Dominik but I think he's busy with exams or such. So I get to
> pretend to be pcmcia maintainer.
>
> "Markus Rechberger" <[email protected]> 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
>>
>> Signed-off-by: Markus Rechberger <[email protected]>
>>
>> --
>> Markus Rechberger
>> Operating System Research Center
>> AMD Saxony LLC & Co. KG
>>
>>
>>
>> [pcmcia-pccard-deadlock-fix.diff text/plain (757B)]
>> index ac00424..c02bf0d 100644
>> --- 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);
>>
>>
>
> This is a pretty sad-looking solution. Does it not mean that sometimes
> user-initiated actions will mysteriously fail?
>
The userspace application should return the appropriate error then. It
can really happen any time when someone tries to eject the pcmcia device
(any time as within 1 minute - never in a normal scenario)
> Are you able to provide a more detailed description of why/how the deadlock
> actually occurs so that perhaps a more robust fix can be implemented?
>
>
There's a description about it in following Email:
http://lkml.org/lkml/2007/2/19/58
Markus