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    Subject[tip:core/rcu] rcu: Make RCU's CPU-stall detector be default
    Commit-ID:  8bfb2f8e655b9d0c45fde679fcd5fd97e34513db
    Gitweb: http://git.kernel.org/tip/8bfb2f8e655b9d0c45fde679fcd5fd97e34513db
    Author: Paul E. McKenney <paulmck@linux.vnet.ibm.com>
    AuthorDate: Wed, 2 Dec 2009 12:10:16 -0800
    Committer: Ingo Molnar <mingo@elte.hu>
    CommitDate: Thu, 3 Dec 2009 11:35:27 +0100

    rcu: Make RCU's CPU-stall detector be default

    The RCU_CPU_STALL_DETECTOR costs almost nothing and has located
    some bugs that might otherwise have been difficult to track
    down. Make it be default for the TREE RCU implementations.

    The vmlinux size impact is limited (on 64-bit x86 defconfig):

    text data bss dec hex filename
    8440248 1260076 995588 10695912 a334e8 vmlinux.before
    8440774 1260060 995588 10696422 a336e6 vmlinux.after

    +526 bytes - acceptable default cost.

    For RAM starved systems, TINY_RCU does not support CPU-stall detection
    and is much smaller, but then again it is a uniprocessor...

    Signed-off-by: Paul E. McKenney <paulmck@linux.vnet.ibm.com>
    Acked-by: Lai Jiangshan <laijs@cn.fujitsu.com>
    Cc: dipankar@in.ibm.com
    Cc: mathieu.desnoyers@polymtl.ca
    Cc: josh@joshtriplett.org
    Cc: dvhltc@us.ibm.com
    Cc: niv@us.ibm.com
    Cc: peterz@infradead.org
    Cc: rostedt@goodmis.org
    Cc: Valdis.Kletnieks@vt.edu
    Cc: dhowells@redhat.com
    LKML-Reference: <12597846162906-git-send-email->
    [ v2: added image size calculations to the changelog ]
    Signed-off-by: Ingo Molnar <mingo@elte.hu>
    ---
    lib/Kconfig.debug | 2 +-
    1 files changed, 1 insertions(+), 1 deletions(-)

    diff --git a/lib/Kconfig.debug b/lib/Kconfig.debug
    index 8911558..50e0e78 100644
    --- a/lib/Kconfig.debug
    +++ b/lib/Kconfig.debug
    @@ -749,7 +749,7 @@ config RCU_TORTURE_TEST_RUNNABLE
    config RCU_CPU_STALL_DETECTOR
    bool "Check for stalled CPUs delaying RCU grace periods"
    depends on TREE_RCU || TREE_PREEMPT_RCU
    - default n
    + default y
    help
    This option causes RCU to printk information on which
    CPUs are delaying the current grace period, but only when

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