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    SubjectRe: [PATCH RFC tip/core/rcu 29/30] rcu: add boot parameter to suppress RCU CPU stall warning messages
    On Wed, Jul 14, 2010 at 01:10:03PM -0700, Paul E. McKenney wrote:
    > Although the RCU CPU stall warning messages are a very good way to alert
    > people to a problem, once alerted, it is sometimes helpful to shut them
    > off in order to avoid obscuring other messages that might be being used
    > to track down the problem. Although you can rebuild the kernel with
    > CONFIG_RCU_CPU_STALL_DETECTOR=n, this is sometimes inconvenient. This
    > commit therefore adds a boot parameter named "rcu_cpu_stall_suppress"
    > that shuts these messages off without requiring a rebuild (though a
    > reboot might be needed for those not brave enough to patch their kernel
    > while it is running).
    >
    > This message-suppression was already in place for the panic case, so this
    > commit need only rename the variable and export it via module_param().
    >
    > Signed-off-by: Paul E. McKenney <paulmck@linux.vnet.ibm.com>
    > ---
    > kernel/rcutree.c | 11 ++++++++---
    > 1 files changed, 8 insertions(+), 3 deletions(-)
    >
    > diff --git a/kernel/rcutree.c b/kernel/rcutree.c
    > index 5b1c3c2..f3d5906 100644
    > --- a/kernel/rcutree.c
    > +++ b/kernel/rcutree.c
    > @@ -143,6 +143,11 @@ module_param(blimit, int, 0);
    > module_param(qhimark, int, 0);
    > module_param(qlowmark, int, 0);
    >
    > +#ifdef CONFIG_RCU_CPU_STALL_DETECTOR
    > +int rcu_cpu_stall_suppress __read_mostly;
    > +module_param(rcu_cpu_stall_suppress, int, 0);
    > +#endif /* #ifdef CONFIG_RCU_CPU_STALL_DETECTOR */

    In theory, you could change the permissions on this module_param from 0
    to 0644, making it appear under /sys as a writable file. That would
    allow changing it at runtime rather than just at boot time. Looking at
    the use of this variable, changing it dynamically should work.

    - Josh Triplett


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