linux-kernel - [PATCH 3.12 035/111] sched: Fix hotplug vs. set_cpus_allowed

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Message-Id: <774f680a78bd9ac6ccac097e7826632e506046a9.1403512281.git.jslaby@suse.cz>
Date:	Mon, 23 Jun 2014 10:31:10 +0200
From:	Jiri Slaby <jslaby@...e.cz>
To:	stable@...r.kernel.org
Cc:	linux-kernel@...r.kernel.org, Lai Jiangshan <laijs@...fujitsu.com>,
	Peter Zijlstra <peterz@...radead.org>,
	Andrew Morton <akpm@...ux-foundation.org>,
	"Gautham R. Shenoy" <ego@...ux.vnet.ibm.com>,
	Linus Torvalds <torvalds@...ux-foundation.org>,
	Michael wang <wangyun@...ux.vnet.ibm.com>,
	Paul Gortmaker <paul.gortmaker@...driver.com>,
	"Rafael J. Wysocki" <rafael.j.wysocki@...el.com>,
	"Srivatsa S. Bhat" <srivatsa.bhat@...ux.vnet.ibm.com>,
	Toshi Kani <toshi.kani@...com>, Ingo Molnar <mingo@...nel.org>,
	Jiri Slaby <jslaby@...e.cz>
Subject: [PATCH 3.12 035/111] sched: Fix hotplug vs. set_cpus_allowed_ptr()

From: Lai Jiangshan <laijs@...fujitsu.com>

3.12-stable review patch.  If anyone has any objections, please let me know.

===============

commit 6acbfb96976fc3350e30d964acb1dbbdf876d55e upstream.

Lai found that:

  WARNING: CPU: 1 PID: 13 at arch/x86/kernel/smp.c:124 native_smp_send_reschedule+0x2d/0x4b()
  ...
  migration_cpu_stop+0x1d/0x22

was caused by set_cpus_allowed_ptr() assuming that cpu_active_mask is
always a sub-set of cpu_online_mask.

This isn't true since 5fbd036b552f ("sched: Cleanup cpu_active madness").

So set active and online at the same time to avoid this particular
problem.

Fixes: 5fbd036b552f ("sched: Cleanup cpu_active madness")
Signed-off-by: Lai Jiangshan <laijs@...fujitsu.com>
Signed-off-by: Peter Zijlstra <peterz@...radead.org>
Cc: Andrew Morton <akpm@...ux-foundation.org>
Cc: Gautham R. Shenoy <ego@...ux.vnet.ibm.com>
Cc: Linus Torvalds <torvalds@...ux-foundation.org>
Cc: Michael wang <wangyun@...ux.vnet.ibm.com>
Cc: Paul Gortmaker <paul.gortmaker@...driver.com>
Cc: Rafael J. Wysocki <rafael.j.wysocki@...el.com>
Cc: Srivatsa S. Bhat <srivatsa.bhat@...ux.vnet.ibm.com>
Cc: Toshi Kani <toshi.kani@...com>
Link: http://lkml.kernel.org/r/53758B12.8060609@cn.fujitsu.com
Signed-off-by: Ingo Molnar <mingo@...nel.org>
Signed-off-by: Jiri Slaby <jslaby@...e.cz>
---
 kernel/cpu.c        | 6 ++++--
 kernel/sched/core.c | 1 -
 2 files changed, 4 insertions(+), 3 deletions(-)

diff --git a/kernel/cpu.c b/kernel/cpu.c
index d7f07a2da5a6..92599d897125 100644
--- a/kernel/cpu.c
+++ b/kernel/cpu.c
@@ -695,10 +695,12 @@ void set_cpu_present(unsigned int cpu, bool present)
 
 void set_cpu_online(unsigned int cpu, bool online)
 {
-	if (online)
+	if (online) {
 		cpumask_set_cpu(cpu, to_cpumask(cpu_online_bits));
-	else
+		cpumask_set_cpu(cpu, to_cpumask(cpu_active_bits));
+	} else {
 		cpumask_clear_cpu(cpu, to_cpumask(cpu_online_bits));
+	}
 }
 
 void set_cpu_active(unsigned int cpu, bool active)
diff --git a/kernel/sched/core.c b/kernel/sched/core.c
index a494ace683e3..07039cba59d9 100644
--- a/kernel/sched/core.c
+++ b/kernel/sched/core.c
@@ -4726,7 +4726,6 @@ static int sched_cpu_active(struct notifier_block *nfb,
 				      unsigned long action, void *hcpu)
 {
 	switch (action & ~CPU_TASKS_FROZEN) {
-	case CPU_STARTING:
 	case CPU_DOWN_FAILED:
 		set_cpu_active((long)hcpu, true);
 		return NOTIFY_OK;
-- 
2.0.0

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