rcu: IPI all CPUs at GP start for strict GPs (933ada2c) · Commits · 戴 / test

Currently, each CPU discovers the beginning of a given grace period on its own time, which is again good for efficiency but bad for fast grace periods. This commit therefore uses on_each_cpu() to IPI each CPU after grace-period initialization in order to inform each CPU of the new grace period in a timely manner, but only in kernels build with CONFIG_RCU_STRICT_GRACE_PERIOD=y. Reported-by Jann Horn <jannh@google.com> Signed-off-by:

Paul E. McKenney <paulmck@kernel.org>

kernel/rcu/tree.c

+13 −0

Original line number	Diff line number	Diff line
		@@ -1695,6 +1695,15 @@ static void rcu_gp_torture_wait(void)
		}
		}

		/*
		* Handler for on_each_cpu() to invoke the target CPU's RCU core
		* processing.
		*/
		static void rcu_strict_gp_boundary(void *unused)
		{
		invoke_rcu_core();
		}

		/*
		* Initialize a new grace period. Return false if no grace period required.
		*/
		@@ -1823,6 +1832,10 @@ static bool rcu_gp_init(void)
		WRITE_ONCE(rcu_state.gp_activity, jiffies);
		}

		// If strict, make all CPUs aware of new grace period.
		if (IS_ENABLED(CONFIG_RCU_STRICT_GRACE_PERIOD))
		on_each_cpu(rcu_strict_gp_boundary, NULL, 0);

		return true;
		}

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