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rcu: Eliminate ->rcu_qs_ctr from the rcu_dynticks structure

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The ->rcu_qs_ctr counter was intended to allow providing a lightweight
report of a quiescent state to all RCU flavors.  But now that there is
only one flavor of RCU in any one running kernel, there is no point in
having this feature.  This commit therefore removes the ->rcu_qs_ctr
field from the rcu_dynticks structure and the ->rcu_qs_ctr_snap field
from the rcu_data structure.  This results in the "rqc" option to the
rcu_fqs trace event no longer being used, so this commit also removes the
"rqc" description from the header comment.

While in the neighborhood, this commit also causes the forward-progress
request .rcu_need_heavy_qs be set one jiffies_till_sched_qs interval
later in the grace period than the first setting of .rcu_urgent_qs.

Signed-off-by: Paul E. McKenney <paulmck@linux.vnet.ibm.com>
This commit is contained in:
Paul E. McKenney
2018-07-11 08:09:28 -07:00
parent c5bacd9417
commit 7e28c5af4e
4 changed files with 17 additions and 48 deletions
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5
include/trace/events/rcu.h
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@@ -393,9 +393,8 @@ TRACE_EVENT(rcu_quiescent_state_report,
* Tracepoint for quiescent states detected by force_quiescent_state().
* These trace events include the type of RCU, the grace-period number
* that was blocked by the CPU, the CPU itself, and the type of quiescent
* state, which can be "dti" for dyntick-idle mode, "kick" when kicking
* a CPU that has been in dyntick-idle mode for too long, or "rqc" if the
* CPU got a quiescent state via its rcu_qs_ctr.
* state, which can be "dti" for dyntick-idle mode or "kick" when kicking
* a CPU that has been in dyntick-idle mode for too long.
*/
TRACE_EVENT(rcu_fqs,