linux-kernel - Re: [PATCH] mmc: sdhci: fix possible scheduling while atomic

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Date:	Fri, 17 Jan 2014 15:16:42 -0800
From:	Andrew Bresticker <abrestic@...omium.org>
To:	John Tobias <john.tobias.ph@...il.com>
Cc:	Philip Rakity <prakity@...dia.com>, Chris Ball <chris@...ntf.net>,
	"linux-mmc@...r.kernel.org" <linux-mmc@...r.kernel.org>,
	"linux-kernel@...r.kernel.org" <linux-kernel@...r.kernel.org>
Subject: Re: [PATCH] mmc: sdhci: fix possible scheduling while atomic

On Fri, Jan 17, 2014 at 3:11 PM, John Tobias <john.tobias.ph@...il.com> wrote:
> There's an existing patch for that...
> http://www.spinics.net/lists/arm-kernel/msg296596.html

Ah, I see.  Looks like it has yet to be picked up...

>
> On Fri, Jan 17, 2014 at 2:58 PM, Philip Rakity <prakity@...dia.com> wrote:
>>
>> On Jan 17, 2014, at 7:57 PM, Andrew Bresticker <abrestic@...omium.org> wrote:
>>
>>> sdhci_execute_tuning() takes host->lock without disabling interrupts.
>>> Use spin_lock_irq{save,restore} instead so that we avoid taking an
>>> interrupt and scheduling while holding host->lock.
>>>
>>> Signed-off-by: Andrew Bresticker <abrestic@...omium.org>
>>> ---
>>> drivers/mmc/host/sdhci.c | 13 +++++++------
>>> 1 file changed, 7 insertions(+), 6 deletions(-)
>>>
>>> diff --git a/drivers/mmc/host/sdhci.c b/drivers/mmc/host/sdhci.c
>>> index ec3eb30..84c80e7 100644
>>> --- a/drivers/mmc/host/sdhci.c
>>> +++ b/drivers/mmc/host/sdhci.c
>>> @@ -1857,12 +1857,13 @@ static int sdhci_execute_tuning(struct mmc_host *mmc, u32 opcode)
>>>       unsigned long timeout;
>>>       int err = 0;
>>>       bool requires_tuning_nonuhs = false;
>>> +     unsigned long flags;
>>>
>>>       host = mmc_priv(mmc);
>>>
>>>       sdhci_runtime_pm_get(host);
>>>       disable_irq(host->irq);
>>> -     spin_lock(&host->lock);
>>> +     spin_lock_irqsave(&host->lock, flags);
>>
>>
>> The disable_irq() call stops the controller from doing interrupts.
>> Please explain what problem you are seeing
>>
>>>
>>>       ctrl = sdhci_readw(host, SDHCI_HOST_CONTROL2);
>>>
>>> @@ -1882,14 +1883,14 @@ static int sdhci_execute_tuning(struct mmc_host *mmc, u32 opcode)
>>>           requires_tuning_nonuhs)
>>>               ctrl |= SDHCI_CTRL_EXEC_TUNING;
>>>       else {
>>> -             spin_unlock(&host->lock);
>>> +             spin_unlock_irqrestore(&host->lock, flags);
>>>               enable_irq(host->irq);
>>>               sdhci_runtime_pm_put(host);
>>>               return 0;
>>>       }
>>>
>>>       if (host->ops->platform_execute_tuning) {
>>> -             spin_unlock(&host->lock);
>>> +             spin_unlock_irqrestore(&host->lock, flags);
>>>               enable_irq(host->irq);
>>>               err = host->ops->platform_execute_tuning(host, opcode);
>>>               sdhci_runtime_pm_put(host);
>>> @@ -1963,7 +1964,7 @@ static int sdhci_execute_tuning(struct mmc_host *mmc, u32 opcode)
>>>               host->cmd = NULL;
>>>               host->mrq = NULL;
>>>
>>> -             spin_unlock(&host->lock);
>>> +             spin_unlock_irqrestore(&host->lock, flags);
>>>               enable_irq(host->irq);
>>>
>>>               /* Wait for Buffer Read Ready interrupt */
>>> @@ -1971,7 +1972,7 @@ static int sdhci_execute_tuning(struct mmc_host *mmc, u32 opcode)
>>>                                       (host->tuning_done == 1),
>>>                                       msecs_to_jiffies(50));
>>>               disable_irq(host->irq);
>>> -             spin_lock(&host->lock);
>>> +             spin_lock_irqsave(&host->lock, flags);
>>>
>>>               if (!host->tuning_done) {
>>>                       pr_info(DRIVER_NAME ": Timeout waiting for "
>>> @@ -2046,7 +2047,7 @@ out:
>>>               err = 0;
>>>
>>>       sdhci_clear_set_irqs(host, SDHCI_INT_DATA_AVAIL, ier);
>>> -     spin_unlock(&host->lock);
>>> +     spin_unlock_irqrestore(&host->lock, flags);
>>>       enable_irq(host->irq);
>>>       sdhci_runtime_pm_put(host);
>>>
>>> --
>>> 1.8.5.2
>>>
>>> --
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>>
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