rcu: Make rcu_future_needs_gp() check all ->need_future_gps[] elements (0ae94e00) · Commits · 戴 / test

Currently, the rcu_future_needs_gp() function checks only the current element of the ->need_future_gps[] array, which might miss elements that were offset from the expected element, for example, due to races with the start or the end of a grace period. This commit therefore makes rcu_future_needs_gp() use the need_any_future_gp() macro to check all of the elements of this array. Signed-off-by:

Paul E. McKenney <paulmck@linux.vnet.ibm.com> Tested-by:

Nicholas Piggin <npiggin@gmail.com>

kernel/rcu/tree.c

+1 −1

Original line number	Diff line number	Diff line
		@@ -720,7 +720,7 @@ static int rcu_future_needs_gp(struct rcu_state *rsp)
		struct rcu_node *rnp = rcu_get_root(rsp);

		lockdep_assert_irqs_disabled();
		return READ_ONCE(need_future_gp_element(rnp, rnp->completed));
		return need_any_future_gp(rnp);
		}

		/*

kernel/rcu/tree.h

+2 −1

Original line number	Diff line number	Diff line
		@@ -169,7 +169,8 @@ struct rcu_node {
		bool __nonzero = false; \
		\
		for (__i = 0; __i < ARRAY_SIZE((rnp)->need_future_gp); __i++) \
		__nonzero = __nonzero \|\| (rnp)->need_future_gp[__i]; \
		__nonzero = __nonzero \|\| \
		READ_ONCE((rnp)->need_future_gp[__i]); \
		__nonzero; \
		})

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