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git://android.git.kernel.org/kernel/common.git android-2.6.29
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commit 5e75ec4ffdf380c69818e4ff7df1c2917cb882e8





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Author: Hidetoshi Seto <seto.hidetoshi@jp.fujitsu.com>





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Date:   Tue Mar 31 16:56:03 2009 +0900





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    posixtimers, sched: Fix posix clock monotonicity





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    Impact: Regression fix (against clock_gettime() backwarding bug)





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    This patch re-introduces a couple of functions, task_sched_runtime





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    and thread_group_sched_runtime, which was once removed at the





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    time of 2.6.28-rc1.





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    These functions protect the sampling of thread/process clock with





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    rq lock.  This rq lock is required not to update rq->clock during





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    the sampling.





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    i.e.





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      The clock_gettime() may return





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       ((accounted runtime before update) + (delta after update))





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      that is less than what it should be.





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    v2 -> v3:





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    	- Rename static helper function __task_delta_exec()





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    	  to do_task_delta_exec() since -tip tree already has





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    	  a __task_delta_exec() of different version.





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    v1 -> v2:





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    	- Revises comments of function and patch description.





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    	- Add note about accuracy of thread group's runtime.





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    Signed-off-by: Hidetoshi Seto <seto.hidetoshi@jp.fujitsu.com>





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    Acked-by: Peter Zijlstra <a.p.zijlstra@chello.nl>





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    Cc: stable@kernel.org	[2.6.28.x][2.6.29.x]





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    LKML-Reference: <49D1CC93.4080401@jp.fujitsu.com>





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    Signed-off-by: Ingo Molnar <mingo@elte.hu>