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

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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>
This commit is contained in:
Joel Fernandes (Google) 2020-06-18 21:36:40 -04:00 committed by Paul E. McKenney
parent c30068f41a
commit a7886e899f
1 changed files with 3 additions and 2 deletions
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5
kernel/rcu/tree.c
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@ -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;
}