From ea24c125fe79fd966a4f59768d3d70142a9eb18d Mon Sep 17 00:00:00 2001 From: "Joel Fernandes (Google)" Date: Sun, 24 Jun 2018 12:34:51 -0700 Subject: [PATCH] doc: Improve rcu_dynticks::dynticks documentation The very useful RCU Data-Structures describes that the dynticks counter of the rcu_dynticks data structure is incremented when we transitions to or from dynticks-idle mode. However it doesn't mention that it is also incremented due to transitions to and from user mode which for dynticks purposes is an extended quiescent state. I found this with tracing calls to rcu_dynticks_eqs_enter which can also happen from rcu_user_enter. Lets add this information to the Data-Structures document. Signed-off-by: Joel Fernandes (Google) Signed-off-by: Paul E. McKenney --- .../RCU/Design/Data-Structures/Data-Structures.html | 8 +++++--- 1 file changed, 5 insertions(+), 3 deletions(-) diff --git a/Documentation/RCU/Design/Data-Structures/Data-Structures.html b/Documentation/RCU/Design/Data-Structures/Data-Structures.html index f5120a00f511..50be87e59937 100644 --- a/Documentation/RCU/Design/Data-Structures/Data-Structures.html +++ b/Documentation/RCU/Design/Data-Structures/Data-Structures.html @@ -1227,9 +1227,11 @@ to overflow the counter, this approach corrects the CPU enters the idle loop from process context.

The ->dynticks field counts the corresponding -CPU's transitions to and from dyntick-idle mode, so that this counter -has an even value when the CPU is in dyntick-idle mode and an odd -value otherwise. +CPU's transitions to and from either dyntick-idle or user mode, so +that this counter has an even value when the CPU is in dyntick-idle +mode or user mode and an odd value otherwise. The transitions to/from +user mode need to be counted for user mode adaptive-ticks support +(see timers/NO_HZ.txt).

The ->rcu_need_heavy_qs field is used to record the fact that the RCU core code would really like to