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McKenney" , rcu@vger.kernel.org, Steven Rostedt , "Uladzislau Rezki (Sony)" Subject: [PATCH 5/7] rcu/trace: Use rsp's gp_seq in acceleration's rcu_grace_period tracepoint Date: Thu, 18 Jun 2020 16:29:53 -0400 Message-Id: <20200618202955.4024-5-joel@joelfernandes.org> X-Mailer: git-send-email 2.27.0.111.gc72c7da667-goog In-Reply-To: <20200618202955.4024-1-joel@joelfernandes.org> References: <20200618202955.4024-1-joel@joelfernandes.org> MIME-Version: 1.0 Content-Transfer-Encoding: 8bit Sender: linux-kernel-owner@vger.kernel.org Precedence: bulk List-ID: X-Mailing-List: linux-kernel@vger.kernel.org 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 rsp's gp_seq instead as it allows one to reason about how the acceleration works. Signed-off-by: Joel Fernandes (Google) --- kernel/rcu/tree.c | 4 ++-- 1 file changed, 2 insertions(+), 2 deletions(-) diff --git a/kernel/rcu/tree.c b/kernel/rcu/tree.c index 81df1b837dd9d..c3bae7a83d792 100644 --- a/kernel/rcu/tree.c +++ b/kernel/rcu/tree.c @@ -1437,9 +1437,9 @@ 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", rdp->gp_seq, TPS("AccWaitCB")); + trace_rcu_grace_period(rcu_state.name, "rsp", rcu_state.gp_seq, TPS("AccWaitCB")); else - trace_rcu_grace_period(rcu_state.name, "rdp", rdp->gp_seq, TPS("AccReadyCB")); + trace_rcu_grace_period(rcu_state.name, "rsp", rcu_state.gp_seq, TPS("AccReadyCB")); /* Count CBs for tracing. */ rcu_segcblist_countseq(&rdp->cblist, cbs, gps); -- 2.27.0.111.gc72c7da667-goog