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| author | Paul E. McKenney <paulmck@kernel.org> | 2020-11-18 16:01:32 -0800 |
|---|---|---|
| committer | Paul E. McKenney <paulmck@kernel.org> | 2021-01-04 13:53:39 -0800 |
| commit | ee7f4a87a18cd3bb141b38e2ef0c3e53253cdf63 (patch) | |
| tree | c00316270f1d5b2feb9f1ff106f2f0bc40c7e3df /Documentation | |
| parent | 5358c9fa54b09b5d3d7811b033aa0838c1bbaaf2 (diff) | |
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>
Diffstat (limited to 'Documentation')
| -rw-r--r-- | Documentation/RCU/Design/Requirements/Requirements.rst | 18 |
1 files changed, 18 insertions, 0 deletions
diff --git a/Documentation/RCU/Design/Requirements/Requirements.rst b/Documentation/RCU/Design/Requirements/Requirements.rst index e8c84fcc0507..93a189ae8592 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 ~~~~~~~~~ |