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    Subject[PATCH 10/16] rcu: Check for RCU_FLAG_GP_INIT bit in gp_flags for spurious wakeup
    Date
    rcu_gp_init() is called once the gp_kthread wakes up on the condition that
    the init bit is set in the gp_flags. For a spurious wakeup we need to check that
    it is actually set. This commit ensures that the RCU_GP_FLAG_INIT bit is set in
    gp_flags.

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

    diff --git a/kernel/rcu/tree.c b/kernel/rcu/tree.c
    index 8d598a2..f8847d9 100644
    --- a/kernel/rcu/tree.c
    +++ b/kernel/rcu/tree.c
    @@ -1600,7 +1600,7 @@ static int rcu_gp_init(struct rcu_state *rsp)
    rcu_bind_gp_kthread();
    raw_spin_lock_irq(&rnp->lock);
    smp_mb__after_unlock_lock();
    - if (!ACCESS_ONCE(rsp->gp_flags)) {
    + if (!(ACCESS_ONCE(rsp->gp_flags) & RCU_GP_FLAG_INIT)) {
    /* Spurious wakeup, tell caller to go back to sleep. */
    raw_spin_unlock_irq(&rnp->lock);
    return 0;
    --
    2.0.0.rc2


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