Re: [PATCH 0/1] Better i2c access latencies in high load situations

[Jean Delvare <khali-PUYAD+kWke1g9hUCZPvPmw@public.gmane.org>]

Hi Mika,

On Wed, 16 Sep 2009 14:17:08 +0300, Mika Kuoppala wrote:
> If low priority thread is holding the bus lock while more high
> priority threads needs the same i2c bus, priority inversion occurs and
> access latency can grow quite large. In my setup i have seen as high as
> 150ms access latencies in some workloads when the actual physical
> transaction is finished in less than 5ms.
> 
> The following patch (in separate email) fixes the priority
> inversion problem described above by converting the i2c bus lock mutex
> to rt_mutex. rt_mutex uses priority inheritance: low priority thread
> holding the mutex will get a kick if high priority thread is trying
> to acquire the lock.

Can you please define "get a kick"? I don't know anything about
rt_mutex.

> 
> Thanks,
> -- Mika
> 
> Mika Kuoppala (1):
>   i2c: Prevent priority inversion on top of bus lock by converting it
>     to rt_mutex
> 
>  drivers/i2c/i2c-core.c |   13 +++++++------
>  include/linux/i2c.h    |    3 +--
>  2 files changed, 8 insertions(+), 8 deletions(-)
> 


-- 
Jean Delvare