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Merge branch 'core-urgent-for-linus' of git://git.kernel.org/pub/scm/linux/kernel/git/tip/tip
Pull RCU fix from Ingo Molnar: "A boot hang fix for the offloaded callback RCU model (RCU_NOCB_CPU=y && (TREE_CPU=y || TREE_PREEMPT_RC)) in certain bootup scenarios" * 'core-urgent-for-linus' of git://git.kernel.org/pub/scm/linux/kernel/git/tip/tip: rcu: Make nocb leader kthreads process pending callbacks after spawning
This commit is contained in:
commit
81368f8bb8
2 changed files with 12 additions and 12 deletions
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@ -358,7 +358,7 @@ struct rcu_data {
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struct rcu_head **nocb_gp_tail;
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long nocb_gp_count;
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long nocb_gp_count_lazy;
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bool nocb_leader_wake; /* Is the nocb leader thread awake? */
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bool nocb_leader_sleep; /* Is the nocb leader thread asleep? */
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struct rcu_data *nocb_next_follower;
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/* Next follower in wakeup chain. */
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@ -2074,9 +2074,9 @@ static void wake_nocb_leader(struct rcu_data *rdp, bool force)
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if (!ACCESS_ONCE(rdp_leader->nocb_kthread))
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return;
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if (!ACCESS_ONCE(rdp_leader->nocb_leader_wake) || force) {
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if (ACCESS_ONCE(rdp_leader->nocb_leader_sleep) || force) {
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/* Prior xchg orders against prior callback enqueue. */
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ACCESS_ONCE(rdp_leader->nocb_leader_wake) = true;
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ACCESS_ONCE(rdp_leader->nocb_leader_sleep) = false;
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wake_up(&rdp_leader->nocb_wq);
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}
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}
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@ -2253,7 +2253,7 @@ static void nocb_leader_wait(struct rcu_data *my_rdp)
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if (!rcu_nocb_poll) {
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trace_rcu_nocb_wake(my_rdp->rsp->name, my_rdp->cpu, "Sleep");
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wait_event_interruptible(my_rdp->nocb_wq,
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ACCESS_ONCE(my_rdp->nocb_leader_wake));
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!ACCESS_ONCE(my_rdp->nocb_leader_sleep));
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/* Memory barrier handled by smp_mb() calls below and repoll. */
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} else if (firsttime) {
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firsttime = false; /* Don't drown trace log with "Poll"! */
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@ -2292,12 +2292,12 @@ static void nocb_leader_wait(struct rcu_data *my_rdp)
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schedule_timeout_interruptible(1);
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/* Rescan in case we were a victim of memory ordering. */
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my_rdp->nocb_leader_wake = false;
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smp_mb(); /* Ensure _wake false before scan. */
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my_rdp->nocb_leader_sleep = true;
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smp_mb(); /* Ensure _sleep true before scan. */
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for (rdp = my_rdp; rdp; rdp = rdp->nocb_next_follower)
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if (ACCESS_ONCE(rdp->nocb_head)) {
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/* Found CB, so short-circuit next wait. */
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my_rdp->nocb_leader_wake = true;
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my_rdp->nocb_leader_sleep = false;
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break;
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}
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goto wait_again;
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@ -2307,17 +2307,17 @@ static void nocb_leader_wait(struct rcu_data *my_rdp)
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rcu_nocb_wait_gp(my_rdp);
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/*
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* We left ->nocb_leader_wake set to reduce cache thrashing.
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* We clear it now, but recheck for new callbacks while
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* We left ->nocb_leader_sleep unset to reduce cache thrashing.
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* We set it now, but recheck for new callbacks while
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* traversing our follower list.
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*/
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my_rdp->nocb_leader_wake = false;
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smp_mb(); /* Ensure _wake false before scan of ->nocb_head. */
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my_rdp->nocb_leader_sleep = true;
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smp_mb(); /* Ensure _sleep true before scan of ->nocb_head. */
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/* Each pass through the following loop wakes a follower, if needed. */
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for (rdp = my_rdp; rdp; rdp = rdp->nocb_next_follower) {
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if (ACCESS_ONCE(rdp->nocb_head))
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my_rdp->nocb_leader_wake = true; /* No need to wait. */
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my_rdp->nocb_leader_sleep = false;/* No need to sleep.*/
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if (!rdp->nocb_gp_head)
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continue; /* No CBs, so no need to wake follower. */
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