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Date: Mon, 24 Aug 2020 22:48:39 -0400 From: "Joel Fernandes (Google)" <joel@...lfernandes.org> To: linux-kernel@...r.kernel.org Cc: "Joel Fernandes (Google)" <joel@...lfernandes.org>, boqun.feng@...il.com, dave@...olabs.net, Ingo Molnar <mingo@...hat.com>, Josh Triplett <josh@...htriplett.org>, Lai Jiangshan <jiangshanlai@...il.com>, Madhuparna Bhowmik <madhuparnabhowmik10@...il.com>, Mathieu Desnoyers <mathieu.desnoyers@...icios.com>, neeraj.iitr10@...il.com, "Paul E. McKenney" <paulmck@...nel.org>, rcu@...r.kernel.org, Steven Rostedt <rostedt@...dmis.org>, "Uladzislau Rezki (Sony)" <urezki@...il.com>, vineethrp@...il.com Subject: [PATCH v4 -rcu 1/4] rcu/segcblist: Do not depend on rcl->len to store the segcb len during merge The donecbs's ->len field is used to store the total count of the segmented callback list's length. This ->len field is then added to the destination segcb list. However, this presents a problem for per-segment length counting which is added in a future patch. This future patch sets the rcl->len field as we move segments of callbacks between source and destination lists, thus becoming incompatible with the donecb's ->len field. This commit therefore avoids depending on the ->len field in this way. IMHO, this is also less error-prone and is more accurate - the donecb's ->len field should be the length of the done segment and not just used as a temporarily variable. Signed-off-by: Joel Fernandes (Google) <joel@...lfernandes.org> --- kernel/rcu/rcu_segcblist.c | 8 ++++++-- 1 file changed, 6 insertions(+), 2 deletions(-) diff --git a/kernel/rcu/rcu_segcblist.c b/kernel/rcu/rcu_segcblist.c index 2d2a6b6b9dfb..b70d4154433c 100644 --- a/kernel/rcu/rcu_segcblist.c +++ b/kernel/rcu/rcu_segcblist.c @@ -513,14 +513,18 @@ void rcu_segcblist_merge(struct rcu_segcblist *dst_rsclp, { struct rcu_cblist donecbs; struct rcu_cblist pendcbs; + long src_len; rcu_cblist_init(&donecbs); rcu_cblist_init(&pendcbs); - rcu_segcblist_extract_count(src_rsclp, &donecbs); + + src_len = rcu_segcblist_xchg_len(src_rsclp, 0); rcu_segcblist_extract_done_cbs(src_rsclp, &donecbs); rcu_segcblist_extract_pend_cbs(src_rsclp, &pendcbs); - rcu_segcblist_insert_count(dst_rsclp, &donecbs); + + rcu_segcblist_add_len(dst_rsclp, src_len); rcu_segcblist_insert_done_cbs(dst_rsclp, &donecbs); rcu_segcblist_insert_pend_cbs(dst_rsclp, &pendcbs); + rcu_segcblist_init(src_rsclp); } -- 2.28.0.297.g1956fa8f8d-goog
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