Commit 4e025f52 authored Aug 06, 2020 by Paul E. McKenney

rcu: IPI all CPUs at GP end for strict GPs



Currently, each CPU discovers the end of a given grace period on its
own time, which is again good for efficiency but bad for fast grace
periods, given that it is things like kfree() within the RCU callbacks
that will cause trouble for pointers leaked from RCU read-side critical
sections.  This commit therefore uses on_each_cpu() to IPI each CPU
after grace-period cleanup in order to inform each CPU of the end of
the old 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>

parent 933ada2c

kernel/rcu/tree.c

+4 −0

Original line number	Diff line number	Diff line
		@@ -2052,6 +2052,10 @@ static void rcu_gp_cleanup(void)
		rcu_state.gp_flags & RCU_GP_FLAG_INIT);
		}
		raw_spin_unlock_irq_rcu_node(rnp);

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

		/*

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