[PATCH] MMC: fix a race between card-detect rescan and clock-gate

[PATCH] MMC: fix a race between card-detect rescan and clock-gate

[Guennadi Liakhovetski]

Currently there is a race in the MMC core between a card-detect
rescan work and the clock-gating work, scheduled from a command
completion. Fix it by removing the dedicated clock-gating mutex and
using the MMC standard locking mechanism instead.

Signed-off-by: Guennadi Liakhovetski <g.liakhovetski@gmx.de>
Cc: Simon Horman <horms@verge.net.au>
Cc: Magnus Damm <damm@opensource.se>
Cc: Linus Walleij <linus.walleij@linaro.org>
---
 drivers/mmc/core/host.c  |    9 ++++-----
 include/linux/mmc/host.h |    1 -
 2 files changed, 4 insertions(+), 6 deletions(-)

diff --git a/drivers/mmc/core/host.c b/drivers/mmc/core/host.c
index 461e6a1..2b200c1 100644
--- a/drivers/mmc/core/host.c
+++ b/drivers/mmc/core/host.c
@@ -94,7 +94,7 @@ static void mmc_host_clk_gate_delayed(struct mmc_host *host)
 		spin_unlock_irqrestore(&host->clk_lock, flags);
 		return;
 	}
-	mutex_lock(&host->clk_gate_mutex);
+	mmc_claim_host(host);
 	spin_lock_irqsave(&host->clk_lock, flags);
 	if (!host->clk_requests) {
 		spin_unlock_irqrestore(&host->clk_lock, flags);
@@ -104,7 +104,7 @@ static void mmc_host_clk_gate_delayed(struct mmc_host *host)
 		pr_debug("%s: gated MCI clock\n", mmc_hostname(host));
 	}
 	spin_unlock_irqrestore(&host->clk_lock, flags);
-	mutex_unlock(&host->clk_gate_mutex);
+	mmc_release_host(host);
 }
 
 /*
@@ -130,7 +130,7 @@ void mmc_host_clk_ungate(struct mmc_host *host)
 {
 	unsigned long flags;
 
-	mutex_lock(&host->clk_gate_mutex);
+	mmc_claim_host(host);
 	spin_lock_irqsave(&host->clk_lock, flags);
 	if (host->clk_gated) {
 		spin_unlock_irqrestore(&host->clk_lock, flags);
@@ -140,7 +140,7 @@ void mmc_host_clk_ungate(struct mmc_host *host)
 	}
 	host->clk_requests++;
 	spin_unlock_irqrestore(&host->clk_lock, flags);
-	mutex_unlock(&host->clk_gate_mutex);
+	mmc_release_host(host);
 }
 
 /**
@@ -215,7 +215,6 @@ static inline void mmc_host_clk_init(struct mmc_host *host)
 	host->clk_gated = false;
 	INIT_WORK(&host->clk_gate_work, mmc_host_clk_gate_work);
 	spin_lock_init(&host->clk_lock);
-	mutex_init(&host->clk_gate_mutex);
 }
 
 /**
diff --git a/include/linux/mmc/host.h b/include/linux/mmc/host.h
index bcb793e..eb792cb 100644
--- a/include/linux/mmc/host.h
+++ b/include/linux/mmc/host.h
@@ -183,7 +183,6 @@ struct mmc_host {
 	struct work_struct	clk_gate_work; /* delayed clock gate */
 	unsigned int		clk_old;	/* old clock value cache */
 	spinlock_t		clk_lock;	/* lock for clk fields */
-	struct mutex		clk_gate_mutex;	/* mutex for clock gating */
 #endif
 
 	/* host specific block data */
-- 
1.7.2.5

[PATCH] MMC: fix a race between card-detect rescan and clock-gate work instances

[Guennadi Liakhovetski]

Currently there is a race in the MMC core between a card-detect
rescan work and the clock-gating work, scheduled from a command
completion. Fix it by removing the dedicated clock-gating mutex and
using the MMC standard locking mechanism instead.

Signed-off-by: Guennadi Liakhovetski <g.liakhovetski@gmx.de>
Cc: Simon Horman <horms@verge.net.au>
Cc: Magnus Damm <damm@opensource.se>
Cc: Linus Walleij <linus.walleij@linaro.org>
---
 drivers/mmc/core/host.c  |    9 ++++-----
 include/linux/mmc/host.h |    1 -
 2 files changed, 4 insertions(+), 6 deletions(-)

diff --git a/drivers/mmc/core/host.c b/drivers/mmc/core/host.c
index 461e6a1..2b200c1 100644
--- a/drivers/mmc/core/host.c
+++ b/drivers/mmc/core/host.c
@@ -94,7 +94,7 @@ static void mmc_host_clk_gate_delayed(struct mmc_host *host)
 		spin_unlock_irqrestore(&host->clk_lock, flags);
 		return;
 	}
-	mutex_lock(&host->clk_gate_mutex);
+	mmc_claim_host(host);
 	spin_lock_irqsave(&host->clk_lock, flags);
 	if (!host->clk_requests) {
 		spin_unlock_irqrestore(&host->clk_lock, flags);
@@ -104,7 +104,7 @@ static void mmc_host_clk_gate_delayed(struct mmc_host *host)
 		pr_debug("%s: gated MCI clock\n", mmc_hostname(host));
 	}
 	spin_unlock_irqrestore(&host->clk_lock, flags);
-	mutex_unlock(&host->clk_gate_mutex);
+	mmc_release_host(host);
 }
 
 /*
@@ -130,7 +130,7 @@ void mmc_host_clk_ungate(struct mmc_host *host)
 {
 	unsigned long flags;
 
-	mutex_lock(&host->clk_gate_mutex);
+	mmc_claim_host(host);
 	spin_lock_irqsave(&host->clk_lock, flags);
 	if (host->clk_gated) {
 		spin_unlock_irqrestore(&host->clk_lock, flags);
@@ -140,7 +140,7 @@ void mmc_host_clk_ungate(struct mmc_host *host)
 	}
 	host->clk_requests++;
 	spin_unlock_irqrestore(&host->clk_lock, flags);
-	mutex_unlock(&host->clk_gate_mutex);
+	mmc_release_host(host);
 }
 
 /**
@@ -215,7 +215,6 @@ static inline void mmc_host_clk_init(struct mmc_host *host)
 	host->clk_gated = false;
 	INIT_WORK(&host->clk_gate_work, mmc_host_clk_gate_work);
 	spin_lock_init(&host->clk_lock);
-	mutex_init(&host->clk_gate_mutex);
 }
 
 /**
diff --git a/include/linux/mmc/host.h b/include/linux/mmc/host.h
index bcb793e..eb792cb 100644
--- a/include/linux/mmc/host.h
+++ b/include/linux/mmc/host.h
@@ -183,7 +183,6 @@ struct mmc_host {
 	struct work_struct	clk_gate_work; /* delayed clock gate */
 	unsigned int		clk_old;	/* old clock value cache */
 	spinlock_t		clk_lock;	/* lock for clk fields */
-	struct mutex		clk_gate_mutex;	/* mutex for clock gating */
 #endif
 
 	/* host specific block data */
-- 
1.7.2.5

Re: [PATCH] MMC: fix a race between card-detect rescan and clock-gate

[Andrei Warkentin]

On Fri, Apr 15, 2011 at 1:08 PM, Guennadi Liakhovetski
<g.liakhovetski@gmx.de> wrote:
> Currently there is a race in the MMC core between a card-detect
> rescan work and the clock-gating work, scheduled from a command
> completion. Fix it by removing the dedicated clock-gating mutex and
> using the MMC standard locking mechanism instead.
>
> Signed-off-by: Guennadi Liakhovetski <g.liakhovetski@gmx.de>
> Cc: Simon Horman <horms@verge.net.au>
> Cc: Magnus Damm <damm@opensource.se>
> Cc: Linus Walleij <linus.walleij@linaro.org>
> ---
>  drivers/mmc/core/host.c  |    9 ++++-----
>  include/linux/mmc/host.h |    1 -
>  2 files changed, 4 insertions(+), 6 deletions(-)
>
> diff --git a/drivers/mmc/core/host.c b/drivers/mmc/core/host.c
> index 461e6a1..2b200c1 100644
> --- a/drivers/mmc/core/host.c
> +++ b/drivers/mmc/core/host.c
> @@ -94,7 +94,7 @@ static void mmc_host_clk_gate_delayed(struct mmc_host *host)
>                spin_unlock_irqrestore(&host->clk_lock, flags);
>                return;
>        }
> -       mutex_lock(&host->clk_gate_mutex);
> +       mmc_claim_host(host);
>        spin_lock_irqsave(&host->clk_lock, flags);
>        if (!host->clk_requests) {
>                spin_unlock_irqrestore(&host->clk_lock, flags);
> @@ -104,7 +104,7 @@ static void mmc_host_clk_gate_delayed(struct mmc_host *host)
>                pr_debug("%s: gated MCI clock\n", mmc_hostname(host));
>        }
>        spin_unlock_irqrestore(&host->clk_lock, flags);
> -       mutex_unlock(&host->clk_gate_mutex);
> +       mmc_release_host(host);
>  }
>
>  /*
> @@ -130,7 +130,7 @@ void mmc_host_clk_ungate(struct mmc_host *host)
>  {
>        unsigned long flags;
>
> -       mutex_lock(&host->clk_gate_mutex);
> +       mmc_claim_host(host);
>        spin_lock_irqsave(&host->clk_lock, flags);
>        if (host->clk_gated) {
>                spin_unlock_irqrestore(&host->clk_lock, flags);
> @@ -140,7 +140,7 @@ void mmc_host_clk_ungate(struct mmc_host *host)
>        }
>        host->clk_requests++;
>        spin_unlock_irqrestore(&host->clk_lock, flags);
> -       mutex_unlock(&host->clk_gate_mutex);
> +       mmc_release_host(host);
>  }
>
>  /**
> @@ -215,7 +215,6 @@ static inline void mmc_host_clk_init(struct mmc_host *host)
>        host->clk_gated = false;
>        INIT_WORK(&host->clk_gate_work, mmc_host_clk_gate_work);
>        spin_lock_init(&host->clk_lock);
> -       mutex_init(&host->clk_gate_mutex);
>  }
>
>  /**
> diff --git a/include/linux/mmc/host.h b/include/linux/mmc/host.h
> index bcb793e..eb792cb 100644
> --- a/include/linux/mmc/host.h
> +++ b/include/linux/mmc/host.h
> @@ -183,7 +183,6 @@ struct mmc_host {
>        struct work_struct      clk_gate_work; /* delayed clock gate */
>        unsigned int            clk_old;        /* old clock value cache */
>        spinlock_t              clk_lock;       /* lock for clk fields */
> -       struct mutex            clk_gate_mutex; /* mutex for clock gating */
>  #endif
>
>        /* host specific block data */
> --
> 1.7.2.5

I've looked at this when Guennadi sent the original email and it looks
good to me FWIW.

A

Re: [PATCH] MMC: fix a race between card-detect rescan and clock-gate work instances

[Andrei Warkentin]

On Fri, Apr 15, 2011 at 1:08 PM, Guennadi Liakhovetski
<g.liakhovetski@gmx.de> wrote:
> Currently there is a race in the MMC core between a card-detect
> rescan work and the clock-gating work, scheduled from a command
> completion. Fix it by removing the dedicated clock-gating mutex and
> using the MMC standard locking mechanism instead.
>
> Signed-off-by: Guennadi Liakhovetski <g.liakhovetski@gmx.de>
> Cc: Simon Horman <horms@verge.net.au>
> Cc: Magnus Damm <damm@opensource.se>
> Cc: Linus Walleij <linus.walleij@linaro.org>
> ---
>  drivers/mmc/core/host.c  |    9 ++++-----
>  include/linux/mmc/host.h |    1 -
>  2 files changed, 4 insertions(+), 6 deletions(-)
>
> diff --git a/drivers/mmc/core/host.c b/drivers/mmc/core/host.c
> index 461e6a1..2b200c1 100644
> --- a/drivers/mmc/core/host.c
> +++ b/drivers/mmc/core/host.c
> @@ -94,7 +94,7 @@ static void mmc_host_clk_gate_delayed(struct mmc_host *host)
>                spin_unlock_irqrestore(&host->clk_lock, flags);
>                return;
>        }
> -       mutex_lock(&host->clk_gate_mutex);
> +       mmc_claim_host(host);
>        spin_lock_irqsave(&host->clk_lock, flags);
>        if (!host->clk_requests) {
>                spin_unlock_irqrestore(&host->clk_lock, flags);
> @@ -104,7 +104,7 @@ static void mmc_host_clk_gate_delayed(struct mmc_host *host)
>                pr_debug("%s: gated MCI clock\n", mmc_hostname(host));
>        }
>        spin_unlock_irqrestore(&host->clk_lock, flags);
> -       mutex_unlock(&host->clk_gate_mutex);
> +       mmc_release_host(host);
>  }
>
>  /*
> @@ -130,7 +130,7 @@ void mmc_host_clk_ungate(struct mmc_host *host)
>  {
>        unsigned long flags;
>
> -       mutex_lock(&host->clk_gate_mutex);
> +       mmc_claim_host(host);
>        spin_lock_irqsave(&host->clk_lock, flags);
>        if (host->clk_gated) {
>                spin_unlock_irqrestore(&host->clk_lock, flags);
> @@ -140,7 +140,7 @@ void mmc_host_clk_ungate(struct mmc_host *host)
>        }
>        host->clk_requests++;
>        spin_unlock_irqrestore(&host->clk_lock, flags);
> -       mutex_unlock(&host->clk_gate_mutex);
> +       mmc_release_host(host);
>  }
>
>  /**
> @@ -215,7 +215,6 @@ static inline void mmc_host_clk_init(struct mmc_host *host)
>        host->clk_gated = false;
>        INIT_WORK(&host->clk_gate_work, mmc_host_clk_gate_work);
>        spin_lock_init(&host->clk_lock);
> -       mutex_init(&host->clk_gate_mutex);
>  }
>
>  /**
> diff --git a/include/linux/mmc/host.h b/include/linux/mmc/host.h
> index bcb793e..eb792cb 100644
> --- a/include/linux/mmc/host.h
> +++ b/include/linux/mmc/host.h
> @@ -183,7 +183,6 @@ struct mmc_host {
>        struct work_struct      clk_gate_work; /* delayed clock gate */
>        unsigned int            clk_old;        /* old clock value cache */
>        spinlock_t              clk_lock;       /* lock for clk fields */
> -       struct mutex            clk_gate_mutex; /* mutex for clock gating */
>  #endif
>
>        /* host specific block data */
> --
> 1.7.2.5

I've looked at this when Guennadi sent the original email and it looks
good to me FWIW.

A

Re: [PATCH] MMC: fix a race between card-detect rescan and clock-gate

[Linus Walleij]

2011/4/15 Guennadi Liakhovetski <g.liakhovetski@gmx.de>:

> Currently there is a race in the MMC core between a card-detect
> rescan work and the clock-gating work, scheduled from a command
> completion. Fix it by removing the dedicated clock-gating mutex and
> using the MMC standard locking mechanism instead.

Acked-by: Linus Walleij <linus.walleij@linaro.org>

Thanks a lot Guennadi!
Linus Walleij

Re: [PATCH] MMC: fix a race between card-detect rescan and clock-gate work instances

[Linus Walleij]

2011/4/15 Guennadi Liakhovetski <g.liakhovetski@gmx.de>:

> Currently there is a race in the MMC core between a card-detect
> rescan work and the clock-gating work, scheduled from a command
> completion. Fix it by removing the dedicated clock-gating mutex and
> using the MMC standard locking mechanism instead.

Acked-by: Linus Walleij <linus.walleij@linaro.org>

Thanks a lot Guennadi!
Linus Walleij

Re: [PATCH] MMC: fix a race between card-detect rescan and clock-gate work instances

[Chris Ball]

Hi Guennadi,

On Fri, Apr 15 2011, Guennadi Liakhovetski wrote:
> Currently there is a race in the MMC core between a card-detect
> rescan work and the clock-gating work, scheduled from a command
> completion. Fix it by removing the dedicated clock-gating mutex and
> using the MMC standard locking mechanism instead.
>
> Signed-off-by: Guennadi Liakhovetski <g.liakhovetski@gmx.de>
> Cc: Simon Horman <horms@verge.net.au>
> Cc: Magnus Damm <damm@opensource.se>
> Cc: Linus Walleij <linus.walleij@linaro.org>

Thanks, pushed to mmc-next with Linus' ACK and a stable@ tag.

- Chris.
-- 
Chris Ball   <cjb@laptop.org>   <http://printf.net/>
One Laptop Per Child

Re: [PATCH] MMC: fix a race between card-detect rescan and clock-gate work instances

[Chris Ball]

Hi Guennadi,

On Fri, Apr 15 2011, Guennadi Liakhovetski wrote:
> Currently there is a race in the MMC core between a card-detect
> rescan work and the clock-gating work, scheduled from a command
> completion. Fix it by removing the dedicated clock-gating mutex and
> using the MMC standard locking mechanism instead.
>
> Signed-off-by: Guennadi Liakhovetski <g.liakhovetski@gmx.de>
> Cc: Simon Horman <horms@verge.net.au>
> Cc: Magnus Damm <damm@opensource.se>
> Cc: Linus Walleij <linus.walleij@linaro.org>

Thanks, pushed to mmc-next with Linus' ACK and a stable@ tag.

- Chris.
-- 
Chris Ball   <cjb@laptop.org>   <http://printf.net/>
One Laptop Per Child

RE: [PATCH] MMC: fix a race between card-detect rescan and clock-gate work instances

[Dong, Chuanxiao]

Hello Liakhovetski,

Right now I am facing some problem during kernel booting which indicate caused by MMC driver. So I think I encountered the race condition you mentioned below.
I have gone through MMC stack code, seems sdhci_set_ios already wrapped by spin lock/unlock, so I am a little not understanding why there is still a race condition?
Is this race condition caused by sdhci_set_ios function reenter or something else?

Thanks for your help on this.

BR
Chuanxiao
-----Original Message-----
From: linux-mmc-owner@vger.kernel.org [mailto:linux-mmc-owner@vger.kernel.org] On Behalf Of Guennadi Liakhovetski
Sent: Saturday, April 16, 2011 2:08 AM
To: linux-sh@vger.kernel.org
Cc: linux-mmc@vger.kernel.org; Magnus Damm; Simon Horman; Linus Walleij
Subject: [PATCH] MMC: fix a race between card-detect rescan and clock-gate work instances

Currently there is a race in the MMC core between a card-detect
rescan work and the clock-gating work, scheduled from a command
completion. Fix it by removing the dedicated clock-gating mutex and
using the MMC standard locking mechanism instead.

Signed-off-by: Guennadi Liakhovetski <g.liakhovetski@gmx.de>
Cc: Simon Horman <horms@verge.net.au>
Cc: Magnus Damm <damm@opensource.se>
Cc: Linus Walleij <linus.walleij@linaro.org>
---
 drivers/mmc/core/host.c  |    9 ++++-----
 include/linux/mmc/host.h |    1 -
 2 files changed, 4 insertions(+), 6 deletions(-)

diff --git a/drivers/mmc/core/host.c b/drivers/mmc/core/host.c
index 461e6a1..2b200c1 100644
--- a/drivers/mmc/core/host.c
+++ b/drivers/mmc/core/host.c
@@ -94,7 +94,7 @@ static void mmc_host_clk_gate_delayed(struct mmc_host *host)
 		spin_unlock_irqrestore(&host->clk_lock, flags);
 		return;
 	}
-	mutex_lock(&host->clk_gate_mutex);
+	mmc_claim_host(host);
 	spin_lock_irqsave(&host->clk_lock, flags);
 	if (!host->clk_requests) {
 		spin_unlock_irqrestore(&host->clk_lock, flags);
@@ -104,7 +104,7 @@ static void mmc_host_clk_gate_delayed(struct mmc_host *host)
 		pr_debug("%s: gated MCI clock\n", mmc_hostname(host));
 	}
 	spin_unlock_irqrestore(&host->clk_lock, flags);
-	mutex_unlock(&host->clk_gate_mutex);
+	mmc_release_host(host);
 }
 
 /*
@@ -130,7 +130,7 @@ void mmc_host_clk_ungate(struct mmc_host *host)
 {
 	unsigned long flags;
 
-	mutex_lock(&host->clk_gate_mutex);
+	mmc_claim_host(host);
 	spin_lock_irqsave(&host->clk_lock, flags);
 	if (host->clk_gated) {
 		spin_unlock_irqrestore(&host->clk_lock, flags);
@@ -140,7 +140,7 @@ void mmc_host_clk_ungate(struct mmc_host *host)
 	}
 	host->clk_requests++;
 	spin_unlock_irqrestore(&host->clk_lock, flags);
-	mutex_unlock(&host->clk_gate_mutex);
+	mmc_release_host(host);
 }
 
 /**
@@ -215,7 +215,6 @@ static inline void mmc_host_clk_init(struct mmc_host *host)
 	host->clk_gated = false;
 	INIT_WORK(&host->clk_gate_work, mmc_host_clk_gate_work);
 	spin_lock_init(&host->clk_lock);
-	mutex_init(&host->clk_gate_mutex);
 }
 
 /**
diff --git a/include/linux/mmc/host.h b/include/linux/mmc/host.h
index bcb793e..eb792cb 100644
--- a/include/linux/mmc/host.h
+++ b/include/linux/mmc/host.h
@@ -183,7 +183,6 @@ struct mmc_host {
 	struct work_struct	clk_gate_work; /* delayed clock gate */
 	unsigned int		clk_old;	/* old clock value cache */
 	spinlock_t		clk_lock;	/* lock for clk fields */
-	struct mutex		clk_gate_mutex;	/* mutex for clock gating */
 #endif
 
 	/* host specific block data */
-- 
1.7.2.5

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RE: [PATCH] MMC: fix a race between card-detect rescan and clock-gate work instances

[Guennadi Liakhovetski]

Hi

On Wed, 11 May 2011, Dong, Chuanxiao wrote:

> Hello Liakhovetski,
> 
> Right now I am facing some problem during kernel booting which indicate 
> caused by MMC driver. So I think I encountered the race condition you 
> mentioned below.

Which kernel are you using? With my patch or without it? What makes you 
think, that your problem is caused by a race in MMC? Races rarely occur 
reproducibly, so, it seems a bit unlikely to me during the boot process.

> I have gone through MMC stack code, seems sdhci_set_ios already wrapped 
> by spin lock/unlock, so I am a little not understanding why there is 
> still a race condition?

Again, are you referring to the kernel before my patch or after?

Thanks
Guennadi

> Is this race condition caused by sdhci_set_ios function reenter or 
> something else?
> 
> Thanks for your help on this.
> 
> BR
> Chuanxiao
> -----Original Message-----
> From: linux-mmc-owner@vger.kernel.org [mailto:linux-mmc-owner@vger.kernel.org] On Behalf Of Guennadi Liakhovetski
> Sent: Saturday, April 16, 2011 2:08 AM
> To: linux-sh@vger.kernel.org
> Cc: linux-mmc@vger.kernel.org; Magnus Damm; Simon Horman; Linus Walleij
> Subject: [PATCH] MMC: fix a race between card-detect rescan and clock-gate work instances
> 
> Currently there is a race in the MMC core between a card-detect
> rescan work and the clock-gating work, scheduled from a command
> completion. Fix it by removing the dedicated clock-gating mutex and
> using the MMC standard locking mechanism instead.
> 
> Signed-off-by: Guennadi Liakhovetski <g.liakhovetski@gmx.de>
> Cc: Simon Horman <horms@verge.net.au>
> Cc: Magnus Damm <damm@opensource.se>
> Cc: Linus Walleij <linus.walleij@linaro.org>
> ---
>  drivers/mmc/core/host.c  |    9 ++++-----
>  include/linux/mmc/host.h |    1 -
>  2 files changed, 4 insertions(+), 6 deletions(-)
> 
> diff --git a/drivers/mmc/core/host.c b/drivers/mmc/core/host.c
> index 461e6a1..2b200c1 100644
> --- a/drivers/mmc/core/host.c
> +++ b/drivers/mmc/core/host.c
> @@ -94,7 +94,7 @@ static void mmc_host_clk_gate_delayed(struct mmc_host *host)
>  		spin_unlock_irqrestore(&host->clk_lock, flags);
>  		return;
>  	}
> -	mutex_lock(&host->clk_gate_mutex);
> +	mmc_claim_host(host);
>  	spin_lock_irqsave(&host->clk_lock, flags);
>  	if (!host->clk_requests) {
>  		spin_unlock_irqrestore(&host->clk_lock, flags);
> @@ -104,7 +104,7 @@ static void mmc_host_clk_gate_delayed(struct mmc_host *host)
>  		pr_debug("%s: gated MCI clock\n", mmc_hostname(host));
>  	}
>  	spin_unlock_irqrestore(&host->clk_lock, flags);
> -	mutex_unlock(&host->clk_gate_mutex);
> +	mmc_release_host(host);
>  }
>  
>  /*
> @@ -130,7 +130,7 @@ void mmc_host_clk_ungate(struct mmc_host *host)
>  {
>  	unsigned long flags;
>  
> -	mutex_lock(&host->clk_gate_mutex);
> +	mmc_claim_host(host);
>  	spin_lock_irqsave(&host->clk_lock, flags);
>  	if (host->clk_gated) {
>  		spin_unlock_irqrestore(&host->clk_lock, flags);
> @@ -140,7 +140,7 @@ void mmc_host_clk_ungate(struct mmc_host *host)
>  	}
>  	host->clk_requests++;
>  	spin_unlock_irqrestore(&host->clk_lock, flags);
> -	mutex_unlock(&host->clk_gate_mutex);
> +	mmc_release_host(host);
>  }
>  
>  /**
> @@ -215,7 +215,6 @@ static inline void mmc_host_clk_init(struct mmc_host *host)
>  	host->clk_gated = false;
>  	INIT_WORK(&host->clk_gate_work, mmc_host_clk_gate_work);
>  	spin_lock_init(&host->clk_lock);
> -	mutex_init(&host->clk_gate_mutex);
>  }
>  
>  /**
> diff --git a/include/linux/mmc/host.h b/include/linux/mmc/host.h
> index bcb793e..eb792cb 100644
> --- a/include/linux/mmc/host.h
> +++ b/include/linux/mmc/host.h
> @@ -183,7 +183,6 @@ struct mmc_host {
>  	struct work_struct	clk_gate_work; /* delayed clock gate */
>  	unsigned int		clk_old;	/* old clock value cache */
>  	spinlock_t		clk_lock;	/* lock for clk fields */
> -	struct mutex		clk_gate_mutex;	/* mutex for clock gating */
>  #endif
>  
>  	/* host specific block data */
> -- 
> 1.7.2.5
> 
> --
> To unsubscribe from this list: send the line "unsubscribe linux-mmc" in
> the body of a message to majordomo@vger.kernel.org
> More majordomo info at  http://vger.kernel.org/majordomo-info.html
> 

---
Guennadi Liakhovetski, Ph.D.
Freelance Open-Source Software Developer
http://www.open-technology.de/

RE: [PATCH] MMC: fix a race between card-detect rescan and clock-gate work instances

[Dong, Chuanxiao]

> -----Original Message-----
> From: Guennadi Liakhovetski [mailto:g.liakhovetski@gmx.de]
> Sent: Wednesday, May 11, 2011 8:26 PM
> To: Dong, Chuanxiao
> Cc: linux-mmc@vger.kernel.org
> Subject: RE: [PATCH] MMC: fix a race between card-detect rescan and clock-gate
> work instances
> 
> Hi
> 
> On Wed, 11 May 2011, Dong, Chuanxiao wrote:
> 
> > Hello Liakhovetski,
> >
> > Right now I am facing some problem during kernel booting which indicate
> > caused by MMC driver. So I think I encountered the race condition you
> > mentioned below.
> 
> Which kernel are you using? With my patch or without it? What makes you
> think, that your problem is caused by a race in MMC? Races rarely occur
> reproducibly, so, it seems a bit unlikely to me during the boot process.
I am using the kernel without your patch, so you can say my kernel is before your patch.
After applied your patch, I never encountered booting failure. So this makes me think I encountered the race condition between card-detect rescan and clock-gate thread.

But I am not quiet understanding what race it is actually. Can you just introduce what race you faced? Is this race condition caused by sdhci_set_ios reenter or something else?

Thanks
Chuanxiao
> 
> > I have gone through MMC stack code, seems sdhci_set_ios already wrapped
> > by spin lock/unlock, so I am a little not understanding why there is
> > still a race condition?
> 
> Again, are you referring to the kernel before my patch or after?
> 
> Thanks
> Guennadi
> 
> > Is this race condition caused by sdhci_set_ios function reenter or
> > something else?
> >
> > Thanks for your help on this.
> >
> > BR
> > Chuanxiao
> > -----Original Message-----
> > From: linux-mmc-owner@vger.kernel.org
> [mailto:linux-mmc-owner@vger.kernel.org] On Behalf Of Guennadi Liakhovetski
> > Sent: Saturday, April 16, 2011 2:08 AM
> > To: linux-sh@vger.kernel.org
> > Cc: linux-mmc@vger.kernel.org; Magnus Damm; Simon Horman; Linus Walleij
> > Subject: [PATCH] MMC: fix a race between card-detect rescan and clock-gate
> work instances
> >
> > Currently there is a race in the MMC core between a card-detect
> > rescan work and the clock-gating work, scheduled from a command
> > completion. Fix it by removing the dedicated clock-gating mutex and
> > using the MMC standard locking mechanism instead.
> >
> > Signed-off-by: Guennadi Liakhovetski <g.liakhovetski@gmx.de>
> > Cc: Simon Horman <horms@verge.net.au>
> > Cc: Magnus Damm <damm@opensource.se>
> > Cc: Linus Walleij <linus.walleij@linaro.org>
> > ---
> >  drivers/mmc/core/host.c  |    9 ++++-----
> >  include/linux/mmc/host.h |    1 -
> >  2 files changed, 4 insertions(+), 6 deletions(-)
> >
> > diff --git a/drivers/mmc/core/host.c b/drivers/mmc/core/host.c
> > index 461e6a1..2b200c1 100644
> > --- a/drivers/mmc/core/host.c
> > +++ b/drivers/mmc/core/host.c
> > @@ -94,7 +94,7 @@ static void mmc_host_clk_gate_delayed(struct mmc_host
> *host)
> >  		spin_unlock_irqrestore(&host->clk_lock, flags);
> >  		return;
> >  	}
> > -	mutex_lock(&host->clk_gate_mutex);
> > +	mmc_claim_host(host);
> >  	spin_lock_irqsave(&host->clk_lock, flags);
> >  	if (!host->clk_requests) {
> >  		spin_unlock_irqrestore(&host->clk_lock, flags);
> > @@ -104,7 +104,7 @@ static void mmc_host_clk_gate_delayed(struct
> mmc_host *host)
> >  		pr_debug("%s: gated MCI clock\n", mmc_hostname(host));
> >  	}
> >  	spin_unlock_irqrestore(&host->clk_lock, flags);
> > -	mutex_unlock(&host->clk_gate_mutex);
> > +	mmc_release_host(host);
> >  }
> >
> >  /*
> > @@ -130,7 +130,7 @@ void mmc_host_clk_ungate(struct mmc_host *host)
> >  {
> >  	unsigned long flags;
> >
> > -	mutex_lock(&host->clk_gate_mutex);
> > +	mmc_claim_host(host);
> >  	spin_lock_irqsave(&host->clk_lock, flags);
> >  	if (host->clk_gated) {
> >  		spin_unlock_irqrestore(&host->clk_lock, flags);
> > @@ -140,7 +140,7 @@ void mmc_host_clk_ungate(struct mmc_host *host)
> >  	}
> >  	host->clk_requests++;
> >  	spin_unlock_irqrestore(&host->clk_lock, flags);
> > -	mutex_unlock(&host->clk_gate_mutex);
> > +	mmc_release_host(host);
> >  }
> >
> >  /**
> > @@ -215,7 +215,6 @@ static inline void mmc_host_clk_init(struct mmc_host
> *host)
> >  	host->clk_gated = false;
> >  	INIT_WORK(&host->clk_gate_work, mmc_host_clk_gate_work);
> >  	spin_lock_init(&host->clk_lock);
> > -	mutex_init(&host->clk_gate_mutex);
> >  }
> >
> >  /**
> > diff --git a/include/linux/mmc/host.h b/include/linux/mmc/host.h
> > index bcb793e..eb792cb 100644
> > --- a/include/linux/mmc/host.h
> > +++ b/include/linux/mmc/host.h
> > @@ -183,7 +183,6 @@ struct mmc_host {
> >  	struct work_struct	clk_gate_work; /* delayed clock gate */
> >  	unsigned int		clk_old;	/* old clock value cache */
> >  	spinlock_t		clk_lock;	/* lock for clk fields */
> > -	struct mutex		clk_gate_mutex;	/* mutex for clock gating */
> >  #endif
> >
> >  	/* host specific block data */
> > --
> > 1.7.2.5
> >
> > --
> > To unsubscribe from this list: send the line "unsubscribe linux-mmc" in
> > the body of a message to majordomo@vger.kernel.org
> > More majordomo info at  http://vger.kernel.org/majordomo-info.html
> >
> 
> ---
> Guennadi Liakhovetski, Ph.D.
> Freelance Open-Source Software Developer
> http://www.open-technology.de/

RE: [PATCH] MMC: fix a race between card-detect rescan and clock-gate work instances

[Guennadi Liakhovetski]

On Wed, 11 May 2011, Dong, Chuanxiao wrote:

> 
> > -----Original Message-----
> > From: Guennadi Liakhovetski [mailto:g.liakhovetski@gmx.de]
> > Sent: Wednesday, May 11, 2011 8:26 PM
> > To: Dong, Chuanxiao
> > Cc: linux-mmc@vger.kernel.org
> > Subject: RE: [PATCH] MMC: fix a race between card-detect rescan and clock-gate
> > work instances
> > 
> > Hi
> > 
> > On Wed, 11 May 2011, Dong, Chuanxiao wrote:
> > 
> > > Hello Liakhovetski,
> > >
> > > Right now I am facing some problem during kernel booting which indicate
> > > caused by MMC driver. So I think I encountered the race condition you
> > > mentioned below.
> > 
> > Which kernel are you using? With my patch or without it? What makes you
> > think, that your problem is caused by a race in MMC? Races rarely occur
> > reproducibly, so, it seems a bit unlikely to me during the boot process.
> I am using the kernel without your patch, so you can say my kernel is 
> before your patch.
> After applied your patch, I never encountered booting failure. So this 
> makes me think I encountered the race condition between card-detect 
> rescan and clock-gate thread.
> 
> But I am not quiet understanding what race it is actually. Can you just 
> introduce what race you faced? Is this race condition caused by 
> sdhci_set_ios reenter or something else?

Look here for an explanation: 
http://thread.gmane.org/gmane.linux.kernel.mmc/7253

Thanks
Guennadi

> 
> Thanks
> Chuanxiao
> > 
> > > I have gone through MMC stack code, seems sdhci_set_ios already wrapped
> > > by spin lock/unlock, so I am a little not understanding why there is
> > > still a race condition?
> > 
> > Again, are you referring to the kernel before my patch or after?
> > 
> > Thanks
> > Guennadi
> > 
> > > Is this race condition caused by sdhci_set_ios function reenter or
> > > something else?
> > >
> > > Thanks for your help on this.
> > >
> > > BR
> > > Chuanxiao
> > > -----Original Message-----
> > > From: linux-mmc-owner@vger.kernel.org
> > [mailto:linux-mmc-owner@vger.kernel.org] On Behalf Of Guennadi Liakhovetski
> > > Sent: Saturday, April 16, 2011 2:08 AM
> > > To: linux-sh@vger.kernel.org
> > > Cc: linux-mmc@vger.kernel.org; Magnus Damm; Simon Horman; Linus Walleij
> > > Subject: [PATCH] MMC: fix a race between card-detect rescan and clock-gate
> > work instances
> > >
> > > Currently there is a race in the MMC core between a card-detect
> > > rescan work and the clock-gating work, scheduled from a command
> > > completion. Fix it by removing the dedicated clock-gating mutex and
> > > using the MMC standard locking mechanism instead.
> > >
> > > Signed-off-by: Guennadi Liakhovetski <g.liakhovetski@gmx.de>
> > > Cc: Simon Horman <horms@verge.net.au>
> > > Cc: Magnus Damm <damm@opensource.se>
> > > Cc: Linus Walleij <linus.walleij@linaro.org>
> > > ---
> > >  drivers/mmc/core/host.c  |    9 ++++-----
> > >  include/linux/mmc/host.h |    1 -
> > >  2 files changed, 4 insertions(+), 6 deletions(-)
> > >
> > > diff --git a/drivers/mmc/core/host.c b/drivers/mmc/core/host.c
> > > index 461e6a1..2b200c1 100644
> > > --- a/drivers/mmc/core/host.c
> > > +++ b/drivers/mmc/core/host.c
> > > @@ -94,7 +94,7 @@ static void mmc_host_clk_gate_delayed(struct mmc_host
> > *host)
> > >  		spin_unlock_irqrestore(&host->clk_lock, flags);
> > >  		return;
> > >  	}
> > > -	mutex_lock(&host->clk_gate_mutex);
> > > +	mmc_claim_host(host);
> > >  	spin_lock_irqsave(&host->clk_lock, flags);
> > >  	if (!host->clk_requests) {
> > >  		spin_unlock_irqrestore(&host->clk_lock, flags);
> > > @@ -104,7 +104,7 @@ static void mmc_host_clk_gate_delayed(struct
> > mmc_host *host)
> > >  		pr_debug("%s: gated MCI clock\n", mmc_hostname(host));
> > >  	}
> > >  	spin_unlock_irqrestore(&host->clk_lock, flags);
> > > -	mutex_unlock(&host->clk_gate_mutex);
> > > +	mmc_release_host(host);
> > >  }
> > >
> > >  /*
> > > @@ -130,7 +130,7 @@ void mmc_host_clk_ungate(struct mmc_host *host)
> > >  {
> > >  	unsigned long flags;
> > >
> > > -	mutex_lock(&host->clk_gate_mutex);
> > > +	mmc_claim_host(host);
> > >  	spin_lock_irqsave(&host->clk_lock, flags);
> > >  	if (host->clk_gated) {
> > >  		spin_unlock_irqrestore(&host->clk_lock, flags);
> > > @@ -140,7 +140,7 @@ void mmc_host_clk_ungate(struct mmc_host *host)
> > >  	}
> > >  	host->clk_requests++;
> > >  	spin_unlock_irqrestore(&host->clk_lock, flags);
> > > -	mutex_unlock(&host->clk_gate_mutex);
> > > +	mmc_release_host(host);
> > >  }
> > >
> > >  /**
> > > @@ -215,7 +215,6 @@ static inline void mmc_host_clk_init(struct mmc_host
> > *host)
> > >  	host->clk_gated = false;
> > >  	INIT_WORK(&host->clk_gate_work, mmc_host_clk_gate_work);
> > >  	spin_lock_init(&host->clk_lock);
> > > -	mutex_init(&host->clk_gate_mutex);
> > >  }
> > >
> > >  /**
> > > diff --git a/include/linux/mmc/host.h b/include/linux/mmc/host.h
> > > index bcb793e..eb792cb 100644
> > > --- a/include/linux/mmc/host.h
> > > +++ b/include/linux/mmc/host.h
> > > @@ -183,7 +183,6 @@ struct mmc_host {
> > >  	struct work_struct	clk_gate_work; /* delayed clock gate */
> > >  	unsigned int		clk_old;	/* old clock value cache */
> > >  	spinlock_t		clk_lock;	/* lock for clk fields */
> > > -	struct mutex		clk_gate_mutex;	/* mutex for clock gating */
> > >  #endif
> > >
> > >  	/* host specific block data */
> > > --
> > > 1.7.2.5
> > >
> > > --
> > > To unsubscribe from this list: send the line "unsubscribe linux-mmc" in
> > > the body of a message to majordomo@vger.kernel.org
> > > More majordomo info at  http://vger.kernel.org/majordomo-info.html
> > >
> > 
> > ---
> > Guennadi Liakhovetski, Ph.D.
> > Freelance Open-Source Software Developer
> > http://www.open-technology.de/
> 

---
Guennadi Liakhovetski, Ph.D.
Freelance Open-Source Software Developer
http://www.open-technology.de/