[PATCH v2] spi: fix possible deadlock between internal bus locks and bus_lock_flag

[PATCH v2] spi: fix possible deadlock between internal bus locks and bus_lock_flag

[Heiko Stübner]

External users may use spi_bus_lock to get exclusive access. This will
also grab the bus_lock_mutex and may therefore result in a deadlock if
__spi_pump_messages also tries to get the mutex.

Therefore adapt spi_pump_messages as well as spi_sync to preset the
bus_locked parameter according to the master->bus_lock_flag.

Fixes: 49023d2e4ead ("spi: core: Fix deadlock when sending messages")
Signed-off-by: Heiko Stuebner <heiko-4mtYJXux2i+zQB+pC5nmwQ@public.gmane.org>
---
changes in v2:
- move the second check from __spi_pump_messages to its calling functions
  spi_pump_messages and __spi_sync as suggested by Vignesh

 drivers/spi/spi.c | 4 ++--
 1 file changed, 2 insertions(+), 2 deletions(-)

diff --git a/drivers/spi/spi.c b/drivers/spi/spi.c
index de2f2f9..0239b45 100644
--- a/drivers/spi/spi.c
+++ b/drivers/spi/spi.c
@@ -1209,7 +1209,7 @@ static void spi_pump_messages(struct kthread_work *work)
 	struct spi_master *master =
 		container_of(work, struct spi_master, pump_messages);
 
-	__spi_pump_messages(master, true, false);
+	__spi_pump_messages(master, true, master->bus_lock_flag);
 }
 
 static int spi_init_queue(struct spi_master *master)
@@ -2853,7 +2853,7 @@ static int __spi_sync(struct spi_device *spi, struct spi_message *message,
  */
 int spi_sync(struct spi_device *spi, struct spi_message *message)
 {
-	return __spi_sync(spi, message, 0);
+	return __spi_sync(spi, message, spi->master->bus_lock_flag);
 }
 EXPORT_SYMBOL_GPL(spi_sync);
 
-- 
2.6.4


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Re: [PATCH v2] spi: fix possible deadlock between internal bus locks and bus_lock_flag

[Jon Hunter]

On 18/03/16 10:15, Heiko Stübner wrote:
> External users may use spi_bus_lock to get exclusive access. This will
> also grab the bus_lock_mutex and may therefore result in a deadlock if
> __spi_pump_messages also tries to get the mutex.
> 
> Therefore adapt spi_pump_messages as well as spi_sync to preset the
> bus_locked parameter according to the master->bus_lock_flag.
> 
> Fixes: 49023d2e4ead ("spi: core: Fix deadlock when sending messages")
> Signed-off-by: Heiko Stuebner <heiko-4mtYJXux2i+zQB+pC5nmwQ@public.gmane.org>
> ---
> changes in v2:
> - move the second check from __spi_pump_messages to its calling functions
>   spi_pump_messages and __spi_sync as suggested by Vignesh
> 
>  drivers/spi/spi.c | 4 ++--
>  1 file changed, 2 insertions(+), 2 deletions(-)
> 
> diff --git a/drivers/spi/spi.c b/drivers/spi/spi.c
> index de2f2f9..0239b45 100644
> --- a/drivers/spi/spi.c
> +++ b/drivers/spi/spi.c
> @@ -1209,7 +1209,7 @@ static void spi_pump_messages(struct kthread_work *work)
>  	struct spi_master *master =
>  		container_of(work, struct spi_master, pump_messages);
>  
> -	__spi_pump_messages(master, true, false);
> +	__spi_pump_messages(master, true, master->bus_lock_flag);
>  }
>  
>  static int spi_init_queue(struct spi_master *master)
> @@ -2853,7 +2853,7 @@ static int __spi_sync(struct spi_device *spi, struct spi_message *message,
>   */
>  int spi_sync(struct spi_device *spi, struct spi_message *message)
>  {
> -	return __spi_sync(spi, message, 0);
> +	return __spi_sync(spi, message, spi->master->bus_lock_flag);
>  }
>  EXPORT_SYMBOL_GPL(spi_sync);

Acked-by: Jon Hunter <jonathanh-DDmLM1+adcrQT0dZR+AlfA@public.gmane.org>

Thanks for the report and fixing this!

Jon
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Applied "spi: fix possible deadlock between internal bus locks and bus_lock_flag" to the spi tree

[Mark Brown]

The patch

   spi: fix possible deadlock between internal bus locks and bus_lock_flag

has been applied to the spi tree at

   git://git.kernel.org/pub/scm/linux/kernel/git/broonie/spi.git 

All being well this means that it will be integrated into the linux-next
tree (usually sometime in the next 24 hours) and sent to Linus during
the next merge window (or sooner if it is a bug fix), however if
problems are discovered then the patch may be dropped or reverted.  

You may get further e-mails resulting from automated or manual testing
and review of the tree, please engage with people reporting problems and
send followup patches addressing any issues that are reported if needed.

If any updates are required or you are submitting further changes they
should be sent as incremental updates against current git, existing
patches will not be replaced.

Please add any relevant lists and maintainers to the CCs when replying
to this mail.

Thanks,
Mark

>From 24c8cd1b081286fd34340f0e1fc68a774a5a775f Mon Sep 17 00:00:00 2001
From: =?UTF-8?q?Heiko=20St=C3=BCbner?= <heiko-4mtYJXux2i+zQB+pC5nmwQ@public.gmane.org>
Date: Fri, 18 Mar 2016 11:15:11 +0100
Subject: [PATCH] spi: fix possible deadlock between internal bus locks and
 bus_lock_flag

External users may use spi_bus_lock to get exclusive access. This will
also grab the bus_lock_mutex and may therefore result in a deadlock if
__spi_pump_messages also tries to get the mutex.

Therefore adapt spi_pump_messages as well as spi_sync to preset the
bus_locked parameter according to the master->bus_lock_flag.

Fixes: 49023d2e4ead ("spi: core: Fix deadlock when sending messages")
Signed-off-by: Heiko Stuebner <heiko-4mtYJXux2i+zQB+pC5nmwQ@public.gmane.org>
Signed-off-by: Mark Brown <broonie-DgEjT+Ai2ygdnm+yROfE0A@public.gmane.org>
---
 drivers/spi/spi.c | 4 ++--
 1 file changed, 2 insertions(+), 2 deletions(-)

diff --git a/drivers/spi/spi.c b/drivers/spi/spi.c
index de2f2f90d799..0239b45eed92 100644
--- a/drivers/spi/spi.c
+++ b/drivers/spi/spi.c
@@ -1209,7 +1209,7 @@ static void spi_pump_messages(struct kthread_work *work)
 	struct spi_master *master =
 		container_of(work, struct spi_master, pump_messages);
 
-	__spi_pump_messages(master, true, false);
+	__spi_pump_messages(master, true, master->bus_lock_flag);
 }
 
 static int spi_init_queue(struct spi_master *master)
@@ -2853,7 +2853,7 @@ static int __spi_sync(struct spi_device *spi, struct spi_message *message,
  */
 int spi_sync(struct spi_device *spi, struct spi_message *message)
 {
-	return __spi_sync(spi, message, 0);
+	return __spi_sync(spi, message, spi->master->bus_lock_flag);
 }
 EXPORT_SYMBOL_GPL(spi_sync);
 
-- 
2.7.0

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Re: [PATCH v2] spi: fix possible deadlock between internal bus locks and bus_lock_flag

[Kevin Hilman]

Heiko Stübner <heiko-4mtYJXux2i+zQB+pC5nmwQ@public.gmane.org> writes:

> External users may use spi_bus_lock to get exclusive access. This will
> also grab the bus_lock_mutex and may therefore result in a deadlock if
> __spi_pump_messages also tries to get the mutex.
>
> Therefore adapt spi_pump_messages as well as spi_sync to preset the
> bus_locked parameter according to the master->bus_lock_flag.
>
> Fixes: 49023d2e4ead ("spi: core: Fix deadlock when sending messages")
> Signed-off-by: Heiko Stuebner <heiko-4mtYJXux2i+zQB+pC5nmwQ@public.gmane.org>

Tested on rk3288-veyron-jerry and verified that it fixes the boot
failure I reported.

Tested-by: Kevin Hilman <khilman-rdvid1DuHRBWk0Htik3J/w@public.gmane.org>

Kevin
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