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Groups > linux.kernel > #1284368

[PATCH tip/core/rcu 03/13] rcu: Simplify rcu_sched_qs() control flow

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This commit applies an early-exit approach to rcu_sched_qs(), reducing
the nesting level and saving a line of code.

Signed-off-by: Paul E. McKenney <paulmck@linux.vnet.ibm.com>
---
 kernel/rcu/tree.c | 29 ++++++++++++++---------------
 1 file changed, 14 insertions(+), 15 deletions(-)

diff --git a/kernel/rcu/tree.c b/kernel/rcu/tree.c
index 23df2661c899..ed3bc0578cc5 100644
--- a/kernel/rcu/tree.c
+++ b/kernel/rcu/tree.c
@@ -244,22 +244,21 @@ void rcu_sched_qs(void)
 {
 	unsigned long flags;
 
-	if (__this_cpu_read(rcu_sched_data.cpu_no_qs.s)) {
-		trace_rcu_grace_period(TPS("rcu_sched"),
-				       __this_cpu_read(rcu_sched_data.gpnum),
-				       TPS("cpuqs"));
-		__this_cpu_write(rcu_sched_data.cpu_no_qs.b.norm, false);
-		if (!__this_cpu_read(rcu_sched_data.cpu_no_qs.b.exp))
-			return;
-		local_irq_save(flags);
-		if (__this_cpu_read(rcu_sched_data.cpu_no_qs.b.exp)) {
-			__this_cpu_write(rcu_sched_data.cpu_no_qs.b.exp, false);
-			rcu_report_exp_rdp(&rcu_sched_state,
-					   this_cpu_ptr(&rcu_sched_data),
-					   true);
-		}
-		local_irq_restore(flags);
+	if (!__this_cpu_read(rcu_sched_data.cpu_no_qs.s))
+		return;
+	trace_rcu_grace_period(TPS("rcu_sched"),
+			       __this_cpu_read(rcu_sched_data.gpnum),
+			       TPS("cpuqs"));
+	__this_cpu_write(rcu_sched_data.cpu_no_qs.b.norm, false);
+	if (!__this_cpu_read(rcu_sched_data.cpu_no_qs.b.exp))
+		return;
+	local_irq_save(flags);
+	if (__this_cpu_read(rcu_sched_data.cpu_no_qs.b.exp)) {
+		__this_cpu_write(rcu_sched_data.cpu_no_qs.b.exp, false);
+		rcu_report_exp_rdp(&rcu_sched_state,
+				   this_cpu_ptr(&rcu_sched_data), true);
 	}
+	local_irq_restore(flags);
 }
 
 void rcu_bh_qs(void)
-- 
2.5.2

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Thread

[PATCH tip/core/rcu 0/10] Expedited-grace-period changes for 4.5 "Paul E. McKenney" <paulmck@linux.vnet.ibm.com> - 2015-12-05 01:00 +0100
  [PATCH tip/core/rcu 09/13] rcu: Make cpu_needs_another_gp() be bool "Paul E. McKenney" <paulmck@linux.vnet.ibm.com> - 2015-12-05 01:10 +0100
  [PATCH tip/core/rcu 04/13] rcu: Remove lock-acquisition loop from rcu_read_unlock_special() "Paul E. McKenney" <paulmck@linux.vnet.ibm.com> - 2015-12-05 01:10 +0100
  [PATCH tip/core/rcu 01/13] rcu: Move lock_class_key to local scope "Paul E. McKenney" <paulmck@linux.vnet.ibm.com> - 2015-12-05 01:20 +0100
  [PATCH tip/core/rcu 02/13] kernel: Make rcu/tree_trace.c explicitly non-modular "Paul E. McKenney" <paulmck@linux.vnet.ibm.com> - 2015-12-05 01:20 +0100
  [PATCH tip/core/rcu 03/13] rcu: Simplify rcu_sched_qs() control flow "Paul E. McKenney" <paulmck@linux.vnet.ibm.com> - 2015-12-05 01:20 +0100
  [PATCH tip/core/rcu 06/13] rcu: Avoid tick_nohz_active checks on NOCBs CPUs "Paul E. McKenney" <paulmck@linux.vnet.ibm.com> - 2015-12-05 01:20 +0100
  [PATCH tip/core/rcu 07/13] rcu: Stop disabling interrupts in scheduler fastpaths "Paul E. McKenney" <paulmck@linux.vnet.ibm.com> - 2015-12-05 01:20 +0100
  [PATCH tip/core/rcu 05/13] rcu: Fix obsolete rcu_bootup_announce_oddness() comment "Paul E. McKenney" <paulmck@linux.vnet.ibm.com> - 2015-12-05 01:20 +0100
  [PATCH tip/core/rcu 12/13] rcu: Move wakeup out from under rnp->lock "Paul E. McKenney" <paulmck@linux.vnet.ibm.com> - 2015-12-05 01:20 +0100
  [PATCH tip/core/rcu 11/13] rcu: Fix comment for rcu_dereference_raw_notrace "Paul E. McKenney" <paulmck@linux.vnet.ibm.com> - 2015-12-05 01:20 +0100
  [PATCH tip/core/rcu 13/13] rcu: Make rcu_gp_init() be bool rather than int "Paul E. McKenney" <paulmck@linux.vnet.ibm.com> - 2015-12-05 01:20 +0100
  [PATCH tip/core/rcu 08/13] rcu: Eliminate unused rcu_init_one() argument "Paul E. McKenney" <paulmck@linux.vnet.ibm.com> - 2015-12-05 01:20 +0100
  [PATCH tip/core/rcu 10/13] rcu: Don't redundantly disable irqs in rcu_irq_{enter,exit}() "Paul E. McKenney" <paulmck@linux.vnet.ibm.com> - 2015-12-05 01:20 +0100
  Re: [PATCH tip/core/rcu 0/10] Expedited-grace-period changes for 4.5 Josh Triplett <josh@joshtriplett.org> - 2015-12-05 02:10 +0100
    Re: [PATCH tip/core/rcu 0/10] Expedited-grace-period changes for 4.5 "Paul E. McKenney" <paulmck@linux.vnet.ibm.com> - 2015-12-06 03:30 +0100

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