PATCH[2.6.32] scheduler patch

[Sadasivan Shaiju <sshaiju@mvista.com>]

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Hi,

I  work for Montavista (Cavium Inc) as  a  Technical  Lead .  I want to
push some  of the kernel  patches to  rt community (2.6.32 kernel 2.6.33
rt patch)  , so  that  It  will  go  to  the  main line These patches  are
reviewed  and approved  by  our system Architect.  I request  you to
include  in the main line .  These  issues  were  reported  by our
customer CISCO.


Problem Description:
  In some cases the task state of a task is set incorrectly, resulting in
a
  hung task.

Root Cause:
  Trying to claim the BKL while PREEMPT_ACTIVE is set will result in
  __schedule returning immediately in __mutex_lock_common().  This means
  the task state will not be set to running by the wakeup, and it also
means
  that the kernel will just sit there and spin waiting for the mutex,
which
  is bad.

  This occurs in __cond_resched, which calls schedule() with
PREEMPT_ACTIVE
  set.  The other places that call schedule() with PREEMPT_ACTIVE set have
  special code that plays with the BKL.

How Solved:
  To fix this, moved releasing and reclaiming the BKL to outside setting
  the PREEMPT_ACTIVE bit.


I request  you to include the above patch  to  the main line .  If  any
questions  please contact me at  sshaiju@mvista.com
(shaiju_sada@yahoo.com)


Regards,
Shaiju.

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