linux-kernel - [tip:timers/urgent] tick/broadcast: Return busy when IPI is pending

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Date:	Tue, 7 Jul 2015 10:14:34 -0700
From:	tip-bot for Thomas Gleixner <tipbot@...or.com>
To:	linux-tip-commits@...r.kernel.org
Cc:	sudeep.holla@....com, tglx@...utronix.de, peterz@...radead.org,
	Lorenzo.Pieralisi@....com, Catalin.Marinas@....com,
	preeti@...ux.vnet.ibm.com, linux-kernel@...r.kernel.org,
	hpa@...or.com, Suzuki.Poulose@....com, rafael.j.wysocki@...el.com,
	mingo@...nel.org
Subject: [tip:timers/urgent] tick/broadcast:
  Return busy when IPI is pending

Commit-ID:  0cc5281aa592d0020868f6ccaed359b4ad7b2684
Gitweb:     http://git.kernel.org/tip/0cc5281aa592d0020868f6ccaed359b4ad7b2684
Author:     Thomas Gleixner <tglx@...utronix.de>
AuthorDate: Tue, 7 Jul 2015 16:45:15 +0200
Committer:  Thomas Gleixner <tglx@...utronix.de>
CommitDate: Tue, 7 Jul 2015 18:46:48 +0200

tick/broadcast: Return busy when IPI is pending

Tell the idle code not to go deep if the broadcast IPI is about to
arrive.

[ Split out from a larger combo patch ]

Tested-by: Sudeep Holla <sudeep.holla@....com>
Signed-off-by: Thomas Gleixner <tglx@...utronix.de>
Cc: Suzuki Poulose <Suzuki.Poulose@....com>
Cc: Lorenzo Pieralisi <Lorenzo.Pieralisi@....com>
Cc: Catalin Marinas <Catalin.Marinas@....com>
Cc: Rafael J. Wysocki <rafael.j.wysocki@...el.com>
Cc: Peter Zijlstra <peterz@...radead.org>
Cc: Preeti U Murthy <preeti@...ux.vnet.ibm.com>
Cc: Ingo Molnar <mingo@...nel.org>
Link: http://lkml.kernel.org/r/alpine.DEB.2.11.1507070929360.3916@nanos
---
 kernel/time/tick-broadcast.c | 10 +++++++---
 1 file changed, 7 insertions(+), 3 deletions(-)

diff --git a/kernel/time/tick-broadcast.c b/kernel/time/tick-broadcast.c
index da7b40f..70b47bc 100644
--- a/kernel/time/tick-broadcast.c
+++ b/kernel/time/tick-broadcast.c
@@ -725,11 +725,15 @@ int __tick_broadcast_oneshot_control(enum tick_broadcast_state state)
 			 * if the cpu local event is earlier than the
 			 * broadcast event. If the current CPU is in
 			 * the force mask, then we are going to be
-			 * woken by the IPI right away.
+			 * woken by the IPI right away; we return
+			 * busy, so the CPU does not try to go deep
+			 * idle.
 			 */
-			if (!cpumask_test_cpu(cpu, tick_broadcast_force_mask) &&
-			    dev->next_event.tv64 < bc->next_event.tv64)
+			if (cpumask_test_cpu(cpu, tick_broadcast_force_mask)) {
+				ret = -EBUSY;
+			} else if (dev->next_event.tv64 < bc->next_event.tv64) {
 				tick_broadcast_set_event(bc, cpu, dev->next_event);
+			}
 		}
 		/*
 		 * If the current CPU owns the hrtimer broadcast
--
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