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

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Date:	Fri, 17 Jan 2014 23:58:59 +0100
From:	Philip Rakity <prakity@...dia.com>
To:	Andrew Bresticker <abrestic@...omium.org>
CC:	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 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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