Patch "rcu: Remove cond_resched() from Tiny synchronize_sched()" has been added to the 4.9-stable tree

Patch "rcu: Remove cond_resched() from Tiny synchronize_sched()" has been added to the 4.9-stable tree

[gregkh]

This is a note to let you know that I've just added the patch titled

    rcu: Remove cond_resched() from Tiny synchronize_sched()

to the 4.9-stable tree which can be found at:
    http://www.kernel.org/git/?p=linux/kernel/git/stable/stable-queue.git;a=summary

The filename of the patch is:
     rcu-remove-cond_resched-from-tiny-synchronize_sched.patch
and it can be found in the queue-4.9 subdirectory.

If you, or anyone else, feels it should not be added to the stable tree,
please let <stable@vger.kernel.org> know about it.


>From f466ae66fa6a599f9a53b5f9bafea4b8cfffa7fb Mon Sep 17 00:00:00 2001
From: "Paul E. McKenney" <paulmck@linux.vnet.ibm.com>
Date: Mon, 9 Jan 2017 23:23:15 -0800
Subject: rcu: Remove cond_resched() from Tiny synchronize_sched()

From: Paul E. McKenney <paulmck@linux.vnet.ibm.com>

commit f466ae66fa6a599f9a53b5f9bafea4b8cfffa7fb upstream.

It is now legal to invoke synchronize_sched() at early boot, which causes
Tiny RCU's synchronize_sched() to emit spurious splats.  This commit
therefore removes the cond_resched() from Tiny RCU's synchronize_sched().

Fixes: 8b355e3bc140 ("rcu: Drive expedited grace periods from workqueue")
Signed-off-by: Paul E. McKenney <paulmck@linux.vnet.ibm.com>
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>

---
 kernel/rcu/tiny.c |    4 ----
 1 file changed, 4 deletions(-)

--- a/kernel/rcu/tiny.c
+++ b/kernel/rcu/tiny.c
@@ -185,9 +185,6 @@ static __latent_entropy void rcu_process
  * benefits of doing might_sleep() to reduce latency.)
  *
  * Cool, huh?  (Due to Josh Triplett.)
- *
- * But we want to make this a static inline later.  The cond_resched()
- * currently makes this problematic.
  */
 void synchronize_sched(void)
 {
@@ -195,7 +192,6 @@ void synchronize_sched(void)
 			 lock_is_held(&rcu_lock_map) ||
 			 lock_is_held(&rcu_sched_lock_map),
 			 "Illegal synchronize_sched() in RCU read-side critical section");
-	cond_resched();
 }
 EXPORT_SYMBOL_GPL(synchronize_sched);
 


Patches currently in stable-queue which might be from paulmck@linux.vnet.ibm.com are

queue-4.9/rcu-narrow-early-boot-window-of-illegal-synchronous-grace-periods.patch
queue-4.9/rcu-remove-cond_resched-from-tiny-synchronize_sched.patch