Messages in this thread Patch in this message | | | From | "Paul E. McKenney" <> | Subject | [PATCH rcu 07/14] rcu: Comment rcu_gp_init() code waiting for CPU-hotplug operations | Date | Wed, 15 Sep 2021 16:33:36 -0700 |
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Near the beginning of rcu_gp_init() is a per-rcu_node loop that waits for CPU-hotplug operations that might have started before the new grace period did. This commit adds a comment explaining that this wait does not exclude CPU-hotplug operations.
Signed-off-by: Paul E. McKenney <paulmck@kernel.org> --- kernel/rcu/tree.c | 2 ++ 1 file changed, 2 insertions(+)
diff --git a/kernel/rcu/tree.c b/kernel/rcu/tree.c index 0bfebec94277..e6e1b9281530 100644 --- a/kernel/rcu/tree.c +++ b/kernel/rcu/tree.c @@ -1775,6 +1775,8 @@ static noinline_for_stack bool rcu_gp_init(void) */ WRITE_ONCE(rcu_state.gp_state, RCU_GP_ONOFF); rcu_for_each_leaf_node(rnp) { + // Wait for CPU-hotplug operations that might have + // started before this grace period did. smp_mb(); // Pair with barriers used when updating ->ofl_seq to odd values. firstseq = READ_ONCE(rnp->ofl_seq); if (firstseq & 0x1) -- 2.31.1.189.g2e36527f23
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