Commit a7886e89 authored Jun 18, 2020 by Joel Fernandes (Google) Committed by Paul E. McKenney Aug 24, 2020

rcu/trace: Use gp_seq_req in acceleration's rcu_grace_period tracepoint



During acceleration of CB, the rsp's gp_seq is rcu_seq_snap'd. This is
the value used for acceleration - it is the value of gp_seq at which it
is safe the execute all callbacks in the callback list.

The rdp's gp_seq is not very useful for this scenario. Make
rcu_grace_period report the gp_seq_req instead as it allows one to
reason about how the acceleration works.

Signed-off-by: Joel Fernandes (Google) <joel@joelfernandes.org>
Signed-off-by: Paul E. McKenney <paulmck@kernel.org>

parent c30068f4

kernel/rcu/tree.c

+3 −2

Original line number	Diff line number	Diff line
		@@ -1483,9 +1483,10 @@ static bool rcu_accelerate_cbs(struct rcu_node rnp, struct rcu_data rdp)

		/* Trace depending on how much we were able to accelerate. */
		if (rcu_segcblist_restempty(&rdp->cblist, RCU_WAIT_TAIL))
		trace_rcu_grace_period(rcu_state.name, rdp->gp_seq, TPS("AccWaitCB"));
		trace_rcu_grace_period(rcu_state.name, gp_seq_req, TPS("AccWaitCB"));
		else
		trace_rcu_grace_period(rcu_state.name, rdp->gp_seq, TPS("AccReadyCB"));
		trace_rcu_grace_period(rcu_state.name, gp_seq_req, TPS("AccReadyCB"));

		return ret;
		}

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