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| -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 ~~~~~~~~~ |