linux-kernel - [tip:sched/core] sched: Fix hotplug vs set_cpus_allowed

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Date:	Mon, 19 May 2014 06:07:42 -0700
From:	tip-bot for Lai Jiangshan <tipbot@...or.com>
To:	linux-tip-commits@...r.kernel.org
Cc:	linux-kernel@...r.kernel.org, hpa@...or.com, mingo@...nel.org,
	peterz@...radead.org, tglx@...utronix.de, laijs@...fujitsu.com
Subject: [tip:sched/core] sched: Fix hotplug vs set_cpus_allowed_ptr()

Commit-ID:  b961b5eea6f90e269bfdec7cd0dac98b008ae817
Gitweb:     http://git.kernel.org/tip/b961b5eea6f90e269bfdec7cd0dac98b008ae817
Author:     Lai Jiangshan <laijs@...fujitsu.com>
AuthorDate: Fri, 16 May 2014 11:50:42 +0800
Committer:  Thomas Gleixner <tglx@...utronix.de>
CommitDate: Mon, 19 May 2014 21:47:34 +0900

sched: Fix hotplug vs set_cpus_allowed_ptr()

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>
Link: http://lkml.kernel.org/r/53758B12.8060609@cn.fujitsu.com
Signed-off-by: Thomas Gleixner <tglx@...utronix.de>
---
 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 a9e710e..247979a 100644
--- a/kernel/cpu.c
+++ b/kernel/cpu.c
@@ -726,10 +726,12 @@ 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 44e00ab..86f3890 100644
--- a/kernel/sched/core.c
+++ b/kernel/sched/core.c
@@ -5076,7 +5076,6 @@ 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;
--
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