On 12 May 2017 at 09:42, Adrian Hunter <adrian.hunter@xxxxxxxxx> 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@xxxxxxxxxx>
>> ---
>> 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 */
>>
>>
>
