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rcu: Pull rcu_qs_ctr into rcu_dynticks structure

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The rcu_qs_ctr variable is yet another isolated per-CPU variable,
so this commit pulls it into the pre-existing rcu_dynticks per-CPU
structure.

Signed-off-by: Paul E. McKenney <paulmck@linux.vnet.ibm.com>
This commit is contained in:
Paul E. McKenney
2017-01-26 16:18:07 -08:00
parent abb06b9948
commit 9577df9a31
4 changed files with 19 additions and 15 deletions
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12
Documentation/RCU/Design/Data-Structures/Data-Structures.html
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@@ -1105,6 +1105,7 @@ Its fields are as follows:
2 int dynticks_nmi_nesting;
3 atomic_t dynticks;
4 int rcu_sched_qs_mask;
5 unsigned long rcu_qs_ctr;
</pre>
<p>The <tt>-&gt;dynticks_nesting</tt> field counts the
@@ -1123,12 +1124,19 @@ 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.
</p><p>Finally, the <tt>-&gt;rcu_sched_qs_mask</tt> field is used
</p><p>The <tt>-&gt;rcu_sched_qs_mask</tt> field is used
to record the fact that the RCU core code would really like to
see a quiescent state from the corresponding CPU.
see a quiescent state from the corresponding CPU, so much so that
it is willing to call for heavy-weight dyntick-counter operations.
This flag is checked by RCU's context-switch and <tt>cond_resched()</tt>
code, which provide a momentary idle sojourn in response.
</p><p>Finally the <tt>-&gt;rcu_qs_ctr</tt> field is used to record
quiescent states from <tt>cond_resched()</tt>.
Because <tt>cond_resched()</tt> can execute quite frequently, this
must be quite lightweight, as in a non-atomic increment of this
per-CPU field.
<table>
<tr><th>&nbsp;</th></tr>
<tr><th align="left">Quick Quiz:</th></tr>