[RFC,1/3] mmc: sdio: Don't use abort-able claim host method from SDIO IRQ thread

Message ID 1494506343-28572-2-git-send-email-ulf.hansson@linaro.org
State New
Headers show
Series
  • mmc: core: Prepare mmc host locking for blk-mq
Related show

Commit Message

Ulf Hansson May 11, 2017, 12:39 p.m.
In a step to simplify the use of the lock, mmc_claim|release_host(), let's
change the SDIO IRQ thread to move away from using the abort-able claim
host method.

In the SDIO IRQ thread case, we can instead check the numbers of SDIO IRQs
that are currently claimed via host->sdio_irqs, as this field is protected
from updates unless the host is claimed. When host->sdio_irqs has become
zero, it means the SDIO func driver(s) has released the SDIO IRQ, then we
can bail out and stop running the SDIO IRQ thread.

Signed-off-by: Ulf Hansson <ulf.hansson@linaro.org>

---
 drivers/mmc/core/sdio_irq.c | 10 ++++++----
 include/linux/mmc/host.h    |  1 -
 2 files changed, 6 insertions(+), 5 deletions(-)

-- 
2.7.4

Comments

Adrian Hunter May 12, 2017, 7:42 a.m. | #1
On 11/05/17 15:39, Ulf Hansson wrote:
> In a step to simplify the use of the lock, mmc_claim|release_host(), let's

> change the SDIO IRQ thread to move away from using the abort-able claim

> host method.

> 

> In the SDIO IRQ thread case, we can instead check the numbers of SDIO IRQs

> that are currently claimed via host->sdio_irqs, as this field is protected

> from updates unless the host is claimed. When host->sdio_irqs has become

> zero, it means the SDIO func driver(s) has released the SDIO IRQ, then we

> can bail out and stop running the SDIO IRQ thread.


Does that work?  It looks a like kthread_stop() will wait on the thread,
which is waiting to claim the host, which is claimed by the caller of
sdio_card_irq_put() which called kthread_stop() i.e. deadlock.

> 

> Signed-off-by: Ulf Hansson <ulf.hansson@linaro.org>

> ---

>  drivers/mmc/core/sdio_irq.c | 10 ++++++----

>  include/linux/mmc/host.h    |  1 -

>  2 files changed, 6 insertions(+), 5 deletions(-)

> 

> diff --git a/drivers/mmc/core/sdio_irq.c b/drivers/mmc/core/sdio_irq.c

> index 6d4b720..95f7a09 100644

> --- a/drivers/mmc/core/sdio_irq.c

> +++ b/drivers/mmc/core/sdio_irq.c

> @@ -137,9 +137,13 @@ static int sdio_irq_thread(void *_host)

>  		 * holding of the host lock does not cover too much work

>  		 * that doesn't require that lock to be held.

>  		 */

> -		ret = __mmc_claim_host(host, &host->sdio_irq_thread_abort);

> -		if (ret)

> +		mmc_claim_host(host);

> +		if (!host->sdio_irqs) {

> +			ret = 1;

> +			mmc_release_host(host);

>  			break;

> +		}

> +

>  		ret = process_sdio_pending_irqs(host);

>  		host->sdio_irq_pending = false;

>  		mmc_release_host(host);

> @@ -195,7 +199,6 @@ static int sdio_card_irq_get(struct mmc_card *card)

>  

>  	if (!host->sdio_irqs++) {

>  		if (!(host->caps2 & MMC_CAP2_SDIO_IRQ_NOTHREAD)) {

> -			atomic_set(&host->sdio_irq_thread_abort, 0);

>  			host->sdio_irq_thread =

>  				kthread_run(sdio_irq_thread, host,

>  					    "ksdioirqd/%s", mmc_hostname(host));

> @@ -223,7 +226,6 @@ static int sdio_card_irq_put(struct mmc_card *card)

>  

>  	if (!--host->sdio_irqs) {

>  		if (!(host->caps2 & MMC_CAP2_SDIO_IRQ_NOTHREAD)) {

> -			atomic_set(&host->sdio_irq_thread_abort, 1);

>  			kthread_stop(host->sdio_irq_thread);

>  		} else if (host->caps & MMC_CAP_SDIO_IRQ) {

>  			host->ops->enable_sdio_irq(host, 0);

> diff --git a/include/linux/mmc/host.h b/include/linux/mmc/host.h

> index 21385ac..8a4131f 100644

> --- a/include/linux/mmc/host.h

> +++ b/include/linux/mmc/host.h

> @@ -359,7 +359,6 @@ struct mmc_host {

>  	unsigned int		sdio_irqs;

>  	struct task_struct	*sdio_irq_thread;

>  	bool			sdio_irq_pending;

> -	atomic_t		sdio_irq_thread_abort;

>  

>  	mmc_pm_flag_t		pm_flags;	/* requested pm features */

>  

> 


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Ulf Hansson May 15, 2017, 12:51 p.m. | #2
On 12 May 2017 at 09:42, Adrian Hunter <adrian.hunter@intel.com> wrote:
> On 11/05/17 15:39, Ulf Hansson wrote:

>> In a step to simplify the use of the lock, mmc_claim|release_host(), let's

>> change the SDIO IRQ thread to move away from using the abort-able claim

>> host method.

>>

>> In the SDIO IRQ thread case, we can instead check the numbers of SDIO IRQs

>> that are currently claimed via host->sdio_irqs, as this field is protected

>> from updates unless the host is claimed. When host->sdio_irqs has become

>> zero, it means the SDIO func driver(s) has released the SDIO IRQ, then we

>> can bail out and stop running the SDIO IRQ thread.

>

> Does that work?  It looks a like kthread_stop() will wait on the thread,

> which is waiting to claim the host, which is claimed by the caller of

> sdio_card_irq_put() which called kthread_stop() i.e. deadlock.


Adrian, you are right and thanks for your analyze!

Maybe it's better that I first continue with my other series,
converting the kthread to a work/work-queue. As that makes it easier
to move away from using the abort-able claim host API.

Kind regards
Uffe

>

>>

>> Signed-off-by: Ulf Hansson <ulf.hansson@linaro.org>

>> ---

>>  drivers/mmc/core/sdio_irq.c | 10 ++++++----

>>  include/linux/mmc/host.h    |  1 -

>>  2 files changed, 6 insertions(+), 5 deletions(-)

>>

>> diff --git a/drivers/mmc/core/sdio_irq.c b/drivers/mmc/core/sdio_irq.c

>> index 6d4b720..95f7a09 100644

>> --- a/drivers/mmc/core/sdio_irq.c

>> +++ b/drivers/mmc/core/sdio_irq.c

>> @@ -137,9 +137,13 @@ static int sdio_irq_thread(void *_host)

>>                * holding of the host lock does not cover too much work

>>                * that doesn't require that lock to be held.

>>                */

>> -             ret = __mmc_claim_host(host, &host->sdio_irq_thread_abort);

>> -             if (ret)

>> +             mmc_claim_host(host);

>> +             if (!host->sdio_irqs) {

>> +                     ret = 1;

>> +                     mmc_release_host(host);

>>                       break;

>> +             }

>> +

>>               ret = process_sdio_pending_irqs(host);

>>               host->sdio_irq_pending = false;

>>               mmc_release_host(host);

>> @@ -195,7 +199,6 @@ static int sdio_card_irq_get(struct mmc_card *card)

>>

>>       if (!host->sdio_irqs++) {

>>               if (!(host->caps2 & MMC_CAP2_SDIO_IRQ_NOTHREAD)) {

>> -                     atomic_set(&host->sdio_irq_thread_abort, 0);

>>                       host->sdio_irq_thread =

>>                               kthread_run(sdio_irq_thread, host,

>>                                           "ksdioirqd/%s", mmc_hostname(host));

>> @@ -223,7 +226,6 @@ static int sdio_card_irq_put(struct mmc_card *card)

>>

>>       if (!--host->sdio_irqs) {

>>               if (!(host->caps2 & MMC_CAP2_SDIO_IRQ_NOTHREAD)) {

>> -                     atomic_set(&host->sdio_irq_thread_abort, 1);

>>                       kthread_stop(host->sdio_irq_thread);

>>               } else if (host->caps & MMC_CAP_SDIO_IRQ) {

>>                       host->ops->enable_sdio_irq(host, 0);

>> diff --git a/include/linux/mmc/host.h b/include/linux/mmc/host.h

>> index 21385ac..8a4131f 100644

>> --- a/include/linux/mmc/host.h

>> +++ b/include/linux/mmc/host.h

>> @@ -359,7 +359,6 @@ struct mmc_host {

>>       unsigned int            sdio_irqs;

>>       struct task_struct      *sdio_irq_thread;

>>       bool                    sdio_irq_pending;

>> -     atomic_t                sdio_irq_thread_abort;

>>

>>       mmc_pm_flag_t           pm_flags;       /* requested pm features */

>>

>>

>

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diff --git a/drivers/mmc/core/sdio_irq.c b/drivers/mmc/core/sdio_irq.c
index 6d4b720..95f7a09 100644
--- a/drivers/mmc/core/sdio_irq.c
+++ b/drivers/mmc/core/sdio_irq.c
@@ -137,9 +137,13 @@  static int sdio_irq_thread(void *_host)
 		 * holding of the host lock does not cover too much work
 		 * that doesn't require that lock to be held.
 		 */
-		ret = __mmc_claim_host(host, &host->sdio_irq_thread_abort);
-		if (ret)
+		mmc_claim_host(host);
+		if (!host->sdio_irqs) {
+			ret = 1;
+			mmc_release_host(host);
 			break;
+		}
+
 		ret = process_sdio_pending_irqs(host);
 		host->sdio_irq_pending = false;
 		mmc_release_host(host);
@@ -195,7 +199,6 @@  static int sdio_card_irq_get(struct mmc_card *card)
 
 	if (!host->sdio_irqs++) {
 		if (!(host->caps2 & MMC_CAP2_SDIO_IRQ_NOTHREAD)) {
-			atomic_set(&host->sdio_irq_thread_abort, 0);
 			host->sdio_irq_thread =
 				kthread_run(sdio_irq_thread, host,
 					    "ksdioirqd/%s", mmc_hostname(host));
@@ -223,7 +226,6 @@  static int sdio_card_irq_put(struct mmc_card *card)
 
 	if (!--host->sdio_irqs) {
 		if (!(host->caps2 & MMC_CAP2_SDIO_IRQ_NOTHREAD)) {
-			atomic_set(&host->sdio_irq_thread_abort, 1);
 			kthread_stop(host->sdio_irq_thread);
 		} else if (host->caps & MMC_CAP_SDIO_IRQ) {
 			host->ops->enable_sdio_irq(host, 0);
diff --git a/include/linux/mmc/host.h b/include/linux/mmc/host.h
index 21385ac..8a4131f 100644
--- a/include/linux/mmc/host.h
+++ b/include/linux/mmc/host.h
@@ -359,7 +359,6 @@  struct mmc_host {
 	unsigned int		sdio_irqs;
 	struct task_struct	*sdio_irq_thread;
 	bool			sdio_irq_pending;
-	atomic_t		sdio_irq_thread_abort;
 
 	mmc_pm_flag_t		pm_flags;	/* requested pm features */