From: "tip-bot2 for Paul E. McKenney" <tip-bot2@linutronix.de>
To: linux-tip-commits@vger.kernel.org
Cc: Kent Overstreet <kent.overstreet@gmail.com>,
Neeraj Upadhyay <neeraju@codeaurora.org>,
"Paul E. McKenney" <paulmck@kernel.org>,
x86@kernel.org, linux-kernel@vger.kernel.org
Subject: [tip: core/rcu] srcu: Document polling interfaces for Tree SRCU grace periods
Date: Mon, 15 Feb 2021 14:55:44 -0000 [thread overview]
Message-ID: <161340094426.20312.8335816020190823152.tip-bot2@tip-bot2> (raw)
The following commit has been merged into the core/rcu branch of tip:
Commit-ID: ee7f4a87a18cd3bb141b38e2ef0c3e53253cdf63
Gitweb: https://git.kernel.org/tip/ee7f4a87a18cd3bb141b38e2ef0c3e53253cdf63
Author: Paul E. McKenney <paulmck@kernel.org>
AuthorDate: Wed, 18 Nov 2020 16:01:32 -08:00
Committer: Paul E. McKenney <paulmck@kernel.org>
CommitterDate: Mon, 04 Jan 2021 13:53:39 -08:00
srcu: Document polling interfaces for Tree SRCU grace periods
This commit adds requirements documentation for the
get_state_synchronize_srcu(), start_poll_synchronize_srcu(), and
poll_state_synchronize_srcu() functions.
Link: https://lore.kernel.org/rcu/20201112201547.GF3365678@moria.home.lan/
Reported-by: Kent Overstreet <kent.overstreet@gmail.com>
Reviewed-by: Neeraj Upadhyay <neeraju@codeaurora.org>
Signed-off-by: Paul E. McKenney <paulmck@kernel.org>
---
Documentation/RCU/Design/Requirements/Requirements.rst | 18 +++++++++-
1 file changed, 18 insertions(+)
diff --git a/Documentation/RCU/Design/Requirements/Requirements.rst b/Documentation/RCU/Design/Requirements/Requirements.rst
index e8c84fc..93a189a 100644
--- a/Documentation/RCU/Design/Requirements/Requirements.rst
+++ b/Documentation/RCU/Design/Requirements/Requirements.rst
@@ -2600,6 +2600,24 @@ also includes ``DEFINE_SRCU()``, ``DEFINE_STATIC_SRCU()``, and
``init_srcu_struct()`` APIs for defining and initializing
``srcu_struct`` structures.
+More recently, the SRCU API has added polling interfaces:
+
+#. start_poll_synchronize_srcu() returns a cookie identifying
+ the completion of a future SRCU grace period and ensures
+ that this grace period will be started.
+#. poll_state_synchronize_srcu() returns ``true`` iff the
+ specified cookie corresponds to an already-completed
+ SRCU grace period.
+#. get_state_synchronize_srcu() returns a cookie just like
+ start_poll_synchronize_srcu() does, but differs in that
+ it does nothing to ensure that any future SRCU grace period
+ will be started.
+
+These functions are used to avoid unnecessary SRCU grace periods in
+certain types of buffer-cache algorithms having multi-stage age-out
+mechanisms. The idea is that by the time the block has aged completely
+from the cache, an SRCU grace period will be very likely to have elapsed.
+
Tasks RCU
~~~~~~~~~
reply other threads:[~2021-02-15 15:00 UTC|newest]
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