linux-kernel - [PATCH RFC v2 tip/core/rcu 1/2] rcu: Remove cond_resched() from Tiny synchronize

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Date:   Sat, 14 Jan 2017 00:45:53 -0800
From:   "Paul E. McKenney" <paulmck@...ux.vnet.ibm.com>
To:     linux-kernel@...r.kernel.org
Cc:     mingo@...nel.org, jiangshanlai@...il.com, dipankar@...ibm.com,
        akpm@...ux-foundation.org, mathieu.desnoyers@...icios.com,
        josh@...htriplett.org, tglx@...utronix.de, peterz@...radead.org,
        rostedt@...dmis.org, dhowells@...hat.com, edumazet@...gle.com,
        dvhart@...ux.intel.com, fweisbec@...il.com, oleg@...hat.com,
        bobby.prani@...il.com,
        "Paul E. McKenney" <paulmck@...ux.vnet.ibm.com>
Subject: [PATCH RFC v2 tip/core/rcu 1/2] rcu: Remove cond_resched() from Tiny synchronize_sched()

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().

Signed-off-by: Paul E. McKenney <paulmck@...ux.vnet.ibm.com>
---
 kernel/rcu/tiny.c | 4 ----
 1 file changed, 4 deletions(-)

diff --git a/kernel/rcu/tiny.c b/kernel/rcu/tiny.c
index 1898559e6b60..b23a4d076f3d 100644
--- a/kernel/rcu/tiny.c
+++ b/kernel/rcu/tiny.c
@@ -185,9 +185,6 @@ static __latent_entropy void rcu_process_callbacks(struct softirq_action *unused
  * 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);
 
-- 
2.5.2