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-rw-r--r--Documentation/RCU/Design/Expedited-Grace-Periods/ExpSchedFlow.svg18
-rw-r--r--Documentation/RCU/Design/Expedited-Grace-Periods/Expedited-Grace-Periods.html26
2 files changed, 24 insertions, 20 deletions
diff --git a/Documentation/RCU/Design/Expedited-Grace-Periods/ExpSchedFlow.svg b/Documentation/RCU/Design/Expedited-Grace-Periods/ExpSchedFlow.svg
index e4233ac93c2b..6189ffcc6aff 100644
--- a/Documentation/RCU/Design/Expedited-Grace-Periods/ExpSchedFlow.svg
+++ b/Documentation/RCU/Design/Expedited-Grace-Periods/ExpSchedFlow.svg
@@ -328,13 +328,13 @@
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id="namedview90"
showgrid="true"
- inkscape:zoom="0.80021373"
- inkscape:cx="462.49289"
- inkscape:cy="473.6718"
+ inkscape:zoom="0.69092787"
+ inkscape:cx="476.34085"
+ inkscape:cy="712.80957"
inkscape:window-x="770"
inkscape:window-y="24"
inkscape:window-maximized="0"
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+ inkscape:current-layer="g4"
inkscape:snap-grids="false"
fit-margin-top="5"
fit-margin-right="5"
@@ -813,14 +813,18 @@
<text
sodipodi:linespacing="125%"
id="text4110-5-7-6-2-4-0"
- y="841.88086"
+ y="670.74316"
x="1460.1007"
style="font-size:267.24359131px;font-style:normal;font-weight:normal;text-align:center;line-height:125%;letter-spacing:0px;word-spacing:0px;text-anchor:middle;fill:#000000;fill-opacity:1;stroke:none;font-family:Sans"
xml:space="preserve"><tspan
- y="841.88086"
+ y="670.74316"
+ x="1460.1007"
+ sodipodi:role="line"
+ id="tspan4925-1-2-4-5">Request</tspan><tspan
+ y="1004.7976"
x="1460.1007"
sodipodi:role="line"
- id="tspan4925-1-2-4-5">reched_cpu()</tspan></text>
+ id="tspan3100">context switch</tspan></text>
</g>
</g>
</svg>
diff --git a/Documentation/RCU/Design/Expedited-Grace-Periods/Expedited-Grace-Periods.html b/Documentation/RCU/Design/Expedited-Grace-Periods/Expedited-Grace-Periods.html
index 8e4f873b979f..19e7a5fb6b73 100644
--- a/Documentation/RCU/Design/Expedited-Grace-Periods/Expedited-Grace-Periods.html
+++ b/Documentation/RCU/Design/Expedited-Grace-Periods/Expedited-Grace-Periods.html
@@ -72,10 +72,10 @@ will ignore it because idle and offline CPUs are already residing
in quiescent states.
Otherwise, the expedited grace period will use
<tt>smp_call_function_single()</tt> to send the CPU an IPI, which
-is handled by <tt>sync_rcu_exp_handler()</tt>.
+is handled by <tt>rcu_exp_handler()</tt>.
<p>
-However, because this is preemptible RCU, <tt>sync_rcu_exp_handler()</tt>
+However, because this is preemptible RCU, <tt>rcu_exp_handler()</tt>
can check to see if the CPU is currently running in an RCU read-side
critical section.
If not, the handler can immediately report a quiescent state.
@@ -145,19 +145,18 @@ expedited grace period is shown in the following diagram:
<p><img src="ExpSchedFlow.svg" alt="ExpSchedFlow.svg" width="55%">
<p>
-As with RCU-preempt's <tt>synchronize_rcu_expedited()</tt>,
+As with RCU-preempt, RCU-sched's
<tt>synchronize_sched_expedited()</tt> ignores offline and
idle CPUs, again because they are in remotely detectable
quiescent states.
-However, the <tt>synchronize_rcu_expedited()</tt> handler
-is <tt>sync_sched_exp_handler()</tt>, and because the
+However, because the
<tt>rcu_read_lock_sched()</tt> and <tt>rcu_read_unlock_sched()</tt>
leave no trace of their invocation, in general it is not possible to tell
whether or not the current CPU is in an RCU read-side critical section.
-The best that <tt>sync_sched_exp_handler()</tt> can do is to check
+The best that RCU-sched's <tt>rcu_exp_handler()</tt> can do is to check
for idle, on the off-chance that the CPU went idle while the IPI
was in flight.
-If the CPU is idle, then <tt>sync_sched_exp_handler()</tt> reports
+If the CPU is idle, then <tt>rcu_exp_handler()</tt> reports
the quiescent state.
<p> Otherwise, the handler forces a future context switch by setting the
@@ -298,19 +297,18 @@ Instead, the task pushing the grace period forward will include the
idle CPUs in the mask passed to <tt>rcu_report_exp_cpu_mult()</tt>.
<p>
-For RCU-sched, there is an additional check for idle in the IPI
-handler, <tt>sync_sched_exp_handler()</tt>.
+For RCU-sched, there is an additional check:
If the IPI has interrupted the idle loop, then
-<tt>sync_sched_exp_handler()</tt> invokes <tt>rcu_report_exp_rdp()</tt>
+<tt>rcu_exp_handler()</tt> invokes <tt>rcu_report_exp_rdp()</tt>
to report the corresponding quiescent state.
<p>
For RCU-preempt, there is no specific check for idle in the
-IPI handler (<tt>sync_rcu_exp_handler()</tt>), but because
+IPI handler (<tt>rcu_exp_handler()</tt>), but because
RCU read-side critical sections are not permitted within the
-idle loop, if <tt>sync_rcu_exp_handler()</tt> sees that the CPU is within
+idle loop, if <tt>rcu_exp_handler()</tt> sees that the CPU is within
RCU read-side critical section, the CPU cannot possibly be idle.
-Otherwise, <tt>sync_rcu_exp_handler()</tt> invokes
+Otherwise, <tt>rcu_exp_handler()</tt> invokes
<tt>rcu_report_exp_rdp()</tt> to report the corresponding quiescent
state, regardless of whether or not that quiescent state was due to
the CPU being idle.
@@ -625,6 +623,8 @@ checks, but only during the mid-boot dead zone.
<p>
With this refinement, synchronous grace periods can now be used from
task context pretty much any time during the life of the kernel.
+That is, aside from some points in the suspend, hibernate, or shutdown
+code path.
<h3><a name="Summary">
Summary</a></h3>