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    Subject[PATCH 11/16] rcu: Check for spurious wakeup using return value
    Date
    When the gp_kthread wakes up from the wait event, it returns 0 if the wake up is
    due to the condition having been met. This commit checks this return value
    for a spurious wake up before calling rcu_gp_init().

    Signed-off-by: Pranith Kumar <bobby.prani@gmail.com>
    ---
    kernel/rcu/tree.c | 4 ++--
    1 file changed, 2 insertions(+), 2 deletions(-)

    diff --git a/kernel/rcu/tree.c b/kernel/rcu/tree.c
    index f8847d9..3b20ad2 100644
    --- a/kernel/rcu/tree.c
    +++ b/kernel/rcu/tree.c
    @@ -1790,11 +1790,11 @@ static int __noreturn rcu_gp_kthread(void *arg)
    ACCESS_ONCE(rsp->gpnum),
    TPS("reqwait"));
    rsp->gp_state = RCU_GP_WAIT_GPS;
    - wait_event_interruptible(rsp->gp_wq,
    + ret = wait_event_interruptible(rsp->gp_wq,
    ACCESS_ONCE(rsp->gp_flags) &
    RCU_GP_FLAG_INIT);
    /* Locking provides needed memory barrier. */
    - if (rcu_gp_init(rsp))
    + if (!ret && rcu_gp_init(rsp))
    break;
    cond_resched();
    flush_signals(current);
    --
    2.0.0.rc2


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