[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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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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