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    Subject[PATCH RFC tip/core/rcu 12/16] rcu: disable CPU stall warnings upon panic
    Date
    The current RCU CPU stall warnings remain enabled even after a panic
    occurs, which some people have found to be a bit counterproductive.
    This patch therefore uses a notifier to disable stall warnings once a
    panic occurs.

    Signed-off-by: Paul E. McKenney <paulmck@linux.vnet.ibm.com>
    ---
    kernel/rcutree.c | 24 ++++++++++++++++++++++++
    1 files changed, 24 insertions(+), 0 deletions(-)

    diff --git a/kernel/rcutree.c b/kernel/rcutree.c
    index 3623f8e..595fb83 100644
    --- a/kernel/rcutree.c
    +++ b/kernel/rcutree.c
    @@ -449,6 +449,8 @@ static int rcu_implicit_dynticks_qs(struct rcu_data *rdp)

    #ifdef CONFIG_RCU_CPU_STALL_DETECTOR

    +int rcu_cpu_stall_panicking __read_mostly;
    +
    static void record_gp_stall_check_time(struct rcu_state *rsp)
    {
    rsp->gp_start = jiffies;
    @@ -526,6 +528,8 @@ static void check_cpu_stall(struct rcu_state *rsp, struct rcu_data *rdp)
    long delta;
    struct rcu_node *rnp;

    + if (rcu_cpu_stall_panicking)
    + return;
    delta = jiffies - rsp->jiffies_stall;
    rnp = rdp->mynode;
    if ((rnp->qsmask & rdp->grpmask) && delta >= 0) {
    @@ -540,6 +544,21 @@ static void check_cpu_stall(struct rcu_state *rsp, struct rcu_data *rdp)
    }
    }

    +static int rcu_panic(struct notifier_block *this, unsigned long ev, void *ptr)
    +{
    + rcu_cpu_stall_panicking = 1;
    + return NOTIFY_DONE;
    +}
    +
    +static struct notifier_block rcu_panic_block = {
    + .notifier_call = rcu_panic,
    +};
    +
    +static void __init check_cpu_stall_init(void)
    +{
    + atomic_notifier_chain_register(&panic_notifier_list, &rcu_panic_block);
    +}
    +
    #else /* #ifdef CONFIG_RCU_CPU_STALL_DETECTOR */

    static void record_gp_stall_check_time(struct rcu_state *rsp)
    @@ -550,6 +569,10 @@ static void check_cpu_stall(struct rcu_state *rsp, struct rcu_data *rdp)
    {
    }

    +static void __init check_cpu_stall_init(void)
    +{
    +}
    +
    #endif /* #else #ifdef CONFIG_RCU_CPU_STALL_DETECTOR */

    /*
    @@ -1934,6 +1957,7 @@ void __init rcu_init(void)
    cpu_notifier(rcu_cpu_notify, 0);
    for_each_online_cpu(cpu)
    rcu_cpu_notify(NULL, CPU_UP_PREPARE, (void *)(long)cpu);
    + check_cpu_stall_init();
    }

    #include "rcutree_plugin.h"
    --
    1.7.0


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