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| author |   Paul E. McKenney <paulmck@linux.vnet.ibm.com> | 2017-04-27 13:16:15 -0700 |
|---|---|---|
| committer | Paul E. McKenney <paulmck@linux.vnet.ibm.com> | 2017-06-08 08:25:33 -0700 |
| commit | 09f501a0f0b5ad81f79049a31fb71f99f282d663 (patch) | |
| tree | 385263714a74806f97706e8b37cdad190f4f1eb9 /Documentation/RCU | |
| parent | rcutorture: Add "git diff" output to testid.txt file (diff) | |
| download | linux-dev-09f501a0f0b5ad81f79049a31fb71f99f282d663.tar.xz linux-dev-09f501a0f0b5ad81f79049a31fb71f99f282d663.zip | |
srcu: Document auto-expediting requirement
This commit documents the auto-expediting requirement satisfied by
commits 2da4b2a7fd8d ("srcu: Expedite first synchronize_srcu() when idle")
and 22607d66bbc3 ("srcu: Specify auto-expedite holdoff time").
Signed-off-by: Paul E. McKenney <paulmck@linux.vnet.ibm.com>
Diffstat (limited to 'Documentation/RCU')
| -rw-r--r-- | Documentation/RCU/Design/Requirements/Requirements.html | 14 |
1 files changed, 14 insertions, 0 deletions
diff --git a/Documentation/RCU/Design/Requirements/Requirements.html b/Documentation/RCU/Design/Requirements/Requirements.html index f60adf112663..8bbf0bb18389 100644 --- a/Documentation/RCU/Design/Requirements/Requirements.html +++ b/Documentation/RCU/Design/Requirements/Requirements.html @@ -2936,6 +2936,20 @@ to whether or not a CPU is online, which means that <tt>srcu_barrier()</tt> need not exclude CPU-hotplug operations. <p> +SRCU also differs from other RCU flavors in that SRCU's expedited and +non-expedited grace periods are implemented by the same mechanism. +This means that in the current SRCU implementation, expediting a +future grace period has the side effect of expediting all prior +grace periods that have not yet completed. +(But please note that this is a property of the current implementation, +not necessarily of future implementations.) +In addition, if SRCU has been idle for longer than the interval +specified by the <tt>srcutree.exp_holdoff</tt> kernel boot parameter +(25 microseconds by default), +and if a <tt>synchronize_srcu()</tt> invocation ends this idle period, +that invocation will be automatically expedited. + +<p> As of v4.12, SRCU's callbacks are maintained per-CPU, eliminating a locking bottleneck present in prior kernel versions. Although this will allow users to put much heavier stress on |