From: Paul E. McKenney <paulmck@kernel.org>
Date: Thu, 1 Sep 2022 17:55:57 +0000 (-0700)
Subject: Merge branches 'doc.2022.08.31b', 'fixes.2022.08.31b', 'kvfree.2022.08.31b', 'nocb... 
X-Git-Url: http://git.maquefel.me/?a=commitdiff_plain;h=5c0ec4900497f7c9cc12f393c329a52e67bc6b8b;p=linux.git

Merge branches 'doc.2022.08.31b', 'fixes.2022.08.31b', 'kvfree.2022.08.31b', 'nocb.2022.09.01a', 'poll.2022.08.31b', 'poll-srcu.2022.08.31b' and 'tasks.2022.08.31b' into HEAD

doc.2022.08.31b: Documentation updates
fixes.2022.08.31b: Miscellaneous fixes
kvfree.2022.08.31b: kvfree_rcu() updates
nocb.2022.09.01a: NOCB CPU updates
poll.2022.08.31b: Full-oldstate RCU polling grace-period API
poll-srcu.2022.08.31b: Polled SRCU grace-period updates
tasks.2022.08.31b: Tasks RCU updates
---

5c0ec4900497f7c9cc12f393c329a52e67bc6b8b
diff --cc kernel/rcu/tree.c
index 79aea7df4345e,79aea7df4345e,7b90478b752e8,79aea7df4345e,ef15bae3c7c77,79aea7df4345e,11d5aefd16961..6bb8e72bc8151
--- a/kernel/rcu/tree.c
+++ b/kernel/rcu/tree.c
@@@@@@@@ -3616,8 -3616,8 -3632,8 -3616,8 -3688,56 -3616,8 -3616,8 +3704,56 @@@@@@@@ bool poll_state_synchronize_rcu(unsigne
       EXPORT_SYMBOL_GPL(poll_state_synchronize_rcu);
       
       /**
---- -- * cond_synchronize_rcu - Conditionally wait for an RCU grace period
++++ ++ * poll_state_synchronize_rcu_full - Has the specified RCU grace period completed?
++++ ++ * @rgosp: value from get_state_synchronize_rcu_full() or start_poll_synchronize_rcu_full()
  +     *
++++ ++ * If a full RCU grace period has elapsed since the earlier call from
++++ ++ * which *rgosp was obtained, return @true, otherwise return @false.
++++ ++ * If @false is returned, it is the caller's responsibility to invoke this
++++ ++ * function later on until it does return @true.  Alternatively, the caller
++++ ++ * can explicitly wait for a grace period, for example, by passing @rgosp
++++ ++ * to cond_synchronize_rcu() or by directly invoking synchronize_rcu().
++++ ++ *
++++ ++ * Yes, this function does not take counter wrap into account.
++++ ++ * But counter wrap is harmless.  If the counter wraps, we have waited
++++ ++ * for more than a billion grace periods (and way more on a 64-bit
++++ ++ * system!).  Those needing to keep rcu_gp_oldstate values for very
++++ ++ * long time periods (many hours even on 32-bit systems) should check
++++ ++ * them occasionally and either refresh them or set a flag indicating
++++ ++ * that the grace period has completed.  Alternatively, they can use
++++ ++ * get_completed_synchronize_rcu_full() to get a guaranteed-completed
++++ ++ * grace-period state.
++ + ++ *
++++ ++ * This function provides the same memory-ordering guarantees that would
++++ ++ * be provided by a synchronize_rcu() that was invoked at the call to
++++ ++ * the function that provided @rgosp, and that returned at the end of this
++++ ++ * function.  And this guarantee requires that the root rcu_node structure's
++++ ++ * ->gp_seq field be checked instead of that of the rcu_state structure.
++++ ++ * The problem is that the just-ending grace-period's callbacks can be
++++ ++ * invoked between the time that the root rcu_node structure's ->gp_seq
++++ ++ * field is updated and the time that the rcu_state structure's ->gp_seq
++++ ++ * field is updated.  Therefore, if a single synchronize_rcu() is to
++++ ++ * cause a subsequent poll_state_synchronize_rcu_full() to return @true,
++++ ++ * then the root rcu_node structure is the one that needs to be polled.
++++ ++ */
++++ ++bool poll_state_synchronize_rcu_full(struct rcu_gp_oldstate *rgosp)
++++ ++{
++++ ++	struct rcu_node *rnp = rcu_get_root();
++++ ++
++++ ++	smp_mb(); // Order against root rcu_node structure grace-period cleanup.
++++ ++	if (rgosp->rgos_norm == RCU_GET_STATE_COMPLETED ||
++++ ++	    rcu_seq_done_exact(&rnp->gp_seq, rgosp->rgos_norm) ||
++++ ++	    rgosp->rgos_exp == RCU_GET_STATE_COMPLETED ||
++++ ++	    rcu_seq_done_exact(&rcu_state.expedited_sequence, rgosp->rgos_exp)) {
++++ ++		smp_mb(); /* Ensure GP ends before subsequent accesses. */
++++ ++		return true;
++++ ++	}
++++ ++	return false;
++++ ++}
++++ ++EXPORT_SYMBOL_GPL(poll_state_synchronize_rcu_full);
++++ ++
++++ ++/**
++++ ++ * cond_synchronize_rcu - Conditionally wait for an RCU grace period
        * @oldstate: value from get_state_synchronize_rcu(), start_poll_synchronize_rcu(), or start_poll_synchronize_rcu_expedited()
        *
        * If a full RCU grace period has elapsed since the earlier call to