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authorPaul E. McKenney <paulmck@linux.vnet.ibm.com>2017-10-24 08:42:41 -0700
committerPaul E. McKenney <paulmck@linux.vnet.ibm.com>2017-12-04 10:28:59 -0800
commitf2b1760aedba1d8394636ba31b9e864e82527528 (patch)
treed56f3cf3d669e9ffa8e1c57926e8772fc4ce6559 /Documentation/RCU
parent388a4c88064e7e62602b4d92ca127f0b0c9b305a (diff)
downloadlinux-f2b1760aedba1d8394636ba31b9e864e82527528.tar.bz2
doc: Eliminate cond_resched_rcu_qs() in favor of cond_resched()
Now that cond_resched() also provides RCU quiescent states when needed, it can be used in place of cond_resched_rcu_qs(). This commit therefore documents this change. Signed-off-by: Paul E. McKenney <paulmck@linux.vnet.ibm.com>
Diffstat (limited to 'Documentation/RCU')
-rw-r--r--Documentation/RCU/Design/Data-Structures/Data-Structures.html3
-rw-r--r--Documentation/RCU/Design/Requirements/Requirements.html4
-rw-r--r--Documentation/RCU/stallwarn.txt10
3 files changed, 8 insertions, 9 deletions
diff --git a/Documentation/RCU/Design/Data-Structures/Data-Structures.html b/Documentation/RCU/Design/Data-Structures/Data-Structures.html
index 38d6d800761f..412466e4967a 100644
--- a/Documentation/RCU/Design/Data-Structures/Data-Structures.html
+++ b/Documentation/RCU/Design/Data-Structures/Data-Structures.html
@@ -1097,7 +1097,8 @@ will cause the CPU to disregard the values of its counters on
its next exit from idle.
Finally, the <tt>rcu_qs_ctr_snap</tt> field is used to detect
cases where a given operation has resulted in a quiescent state
-for all flavors of RCU, for example, <tt>cond_resched_rcu_qs()</tt>.
+for all flavors of RCU, for example, <tt>cond_resched()</tt>
+when RCU has indicated a need for quiescent states.
<h5>RCU Callback Handling</h5>
diff --git a/Documentation/RCU/Design/Requirements/Requirements.html b/Documentation/RCU/Design/Requirements/Requirements.html
index 62e847bcdcdd..0372e6c54eef 100644
--- a/Documentation/RCU/Design/Requirements/Requirements.html
+++ b/Documentation/RCU/Design/Requirements/Requirements.html
@@ -2797,7 +2797,7 @@ RCU must avoid degrading real-time response for CPU-bound threads, whether
executing in usermode (which is one use case for
<tt>CONFIG_NO_HZ_FULL=y</tt>) or in the kernel.
That said, CPU-bound loops in the kernel must execute
-<tt>cond_resched_rcu_qs()</tt> at least once per few tens of milliseconds
+<tt>cond_resched()</tt> at least once per few tens of milliseconds
in order to avoid receiving an IPI from RCU.
<p>
@@ -3128,7 +3128,7 @@ The solution, in the form of
is to have implicit
read-side critical sections that are delimited by voluntary context
switches, that is, calls to <tt>schedule()</tt>,
-<tt>cond_resched_rcu_qs()</tt>, and
+<tt>cond_resched()</tt>, and
<tt>synchronize_rcu_tasks()</tt>.
In addition, transitions to and from userspace execution also delimit
tasks-RCU read-side critical sections.
diff --git a/Documentation/RCU/stallwarn.txt b/Documentation/RCU/stallwarn.txt
index a08f928c8557..4259f95c3261 100644
--- a/Documentation/RCU/stallwarn.txt
+++ b/Documentation/RCU/stallwarn.txt
@@ -23,12 +23,10 @@ o A CPU looping with preemption disabled. This condition can
o A CPU looping with bottom halves disabled. This condition can
result in RCU-sched and RCU-bh stalls.
-o For !CONFIG_PREEMPT kernels, a CPU looping anywhere in the
- kernel without invoking schedule(). Note that cond_resched()
- does not necessarily prevent RCU CPU stall warnings. Therefore,
- if the looping in the kernel is really expected and desirable
- behavior, you might need to replace some of the cond_resched()
- calls with calls to cond_resched_rcu_qs().
+o For !CONFIG_PREEMPT kernels, a CPU looping anywhere in the kernel
+ without invoking schedule(). If the looping in the kernel is
+ really expected and desirable behavior, you might need to add
+ some calls to cond_resched().
o Booting Linux using a console connection that is too slow to
keep up with the boot-time console-message rate. For example,