linux-kernel - [tip:timers/urgent] tick/broadcast: Sanity check the shutdown of the local clock

lists.openwall.net		lists / announce owl-users owl-dev john-users john-dev passwdqc-users yescrypt popa3d-users / oss-security kernel-hardening musl sabotage tlsify passwords / crypt-dev xvendor / Bugtraq Full-Disclosure linux-kernel linux-netdev linux-ext4 linux-hardening linux-cve-announce PHC
Open Source and information security mailing list archives

Hash Suite: Windows password security audit tool. GUI, reports in PDF.

[<prev] [next>] [<thread-prev] [thread-next>] [day] [month] [year] [list]

Date:	Tue, 7 Jul 2015 10:12:53 -0700
From:	tip-bot for Thomas Gleixner <tipbot@...or.com>
To:	linux-tip-commits@...r.kernel.org
Cc:	Suzuki.Poulose@....com, Lorenzo.Pieralisi@....com,
	rafael.j.wysocki@...el.com, hpa@...or.com, peterz@...radead.org,
	sudeep.holla@....com, Catalin.Marinas@....com,
	linux-kernel@...r.kernel.org, tglx@...utronix.de, mingo@...nel.org,
	preeti@...ux.vnet.ibm.com
Subject: [tip:timers/urgent] tick/broadcast:
  Sanity check the shutdown of the local clock_event

Commit-ID:  e0454311903d3fd0f12a86c9e65d7b271c2bb05d
Gitweb:     http://git.kernel.org/tip/e0454311903d3fd0f12a86c9e65d7b271c2bb05d
Author:     Thomas Gleixner <tglx@...utronix.de>
AuthorDate: Tue, 7 Jul 2015 14:07:27 +0200
Committer:  Thomas Gleixner <tglx@...utronix.de>
CommitDate: Tue, 7 Jul 2015 18:46:47 +0200

tick/broadcast: Sanity check the shutdown of the local clock_event

The broadcast code shuts down the local clock event unconditionally
even if no broadcast device is installed or if the broadcast device is
hrtimer based.

Add proper sanity checks.

[ Split out from a larger combo patch ]

Reported-and-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 | 23 ++++++++++++++++-------
 1 file changed, 16 insertions(+), 7 deletions(-)

diff --git a/kernel/time/tick-broadcast.c b/kernel/time/tick-broadcast.c
index a762040..9877d0b 100644
--- a/kernel/time/tick-broadcast.c
+++ b/kernel/time/tick-broadcast.c
@@ -159,7 +159,7 @@ int tick_device_uses_broadcast(struct clock_event_device *dev, int cpu)
 {
 	struct clock_event_device *bc = tick_broadcast_device.evtdev;
 	unsigned long flags;
-	int ret;
+	int ret = 0;
 
 	raw_spin_lock_irqsave(&tick_broadcast_lock, flags);
 
@@ -221,13 +221,14 @@ int tick_device_uses_broadcast(struct clock_event_device *dev, int cpu)
 			 * If we kept the cpu in the broadcast mask,
 			 * tell the caller to leave the per cpu device
 			 * in shutdown state. The periodic interrupt
-			 * is delivered by the broadcast device.
+			 * is delivered by the broadcast device, if
+			 * the broadcast device exists and is not
+			 * hrtimer based.
 			 */
-			ret = cpumask_test_cpu(cpu, tick_broadcast_mask);
+			if (bc && !(bc->features & CLOCK_EVT_FEAT_HRTIMER))
+				ret = cpumask_test_cpu(cpu, tick_broadcast_mask);
 			break;
 		default:
-			/* Nothing to do */
-			ret = 0;
 			break;
 		}
 	}
@@ -373,8 +374,16 @@ void tick_broadcast_control(enum tick_broadcast_mode mode)
 	case TICK_BROADCAST_ON:
 		cpumask_set_cpu(cpu, tick_broadcast_on);
 		if (!cpumask_test_and_set_cpu(cpu, tick_broadcast_mask)) {
-			if (tick_broadcast_device.mode ==
-			    TICKDEV_MODE_PERIODIC)
+			/*
+			 * Only shutdown the cpu local device, if:
+			 *
+			 * - the broadcast device exists
+			 * - the broadcast device is not a hrtimer based one
+			 * - the broadcast device is in periodic mode to
+			 *   avoid a hickup during switch to oneshot mode
+			 */
+			if (bc && !(bc->features & CLOCK_EVT_FEAT_HRTIMER) &&
+			    tick_broadcast_device.mode == TICKDEV_MODE_PERIODIC)
 				clockevents_shutdown(dev);
 		}
 		break;
--
To unsubscribe from this list: send the line "unsubscribe linux-kernel" in
the body of a message to majordomo@...r.kernel.org
More majordomo info at  http://vger.kernel.org/majordomo-info.html
Please read the FAQ at  http://www.tux.org/lkml/