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Message-ID: <tip-9ee349ad6d326df3633d43f54202427295999c47@git.kernel.org>
Date: Wed, 16 Dec 2009 18:36:50 GMT
From: tip-bot for Xiaotian Feng <dfeng@...hat.com>
To: linux-tip-commits@...r.kernel.org
Cc: linux-kernel@...r.kernel.org, hpa@...or.com, mingo@...hat.com,
a.p.zijlstra@...llo.nl, efault@....de, sachinp@...ibm.com,
tglx@...utronix.de, dfeng@...hat.com, mingo@...e.hu
Subject: [tip:sched/urgent] sched: Fix set_cpu_active() in cpu_down()
Commit-ID: 9ee349ad6d326df3633d43f54202427295999c47
Gitweb: http://git.kernel.org/tip/9ee349ad6d326df3633d43f54202427295999c47
Author: Xiaotian Feng <dfeng@...hat.com>
AuthorDate: Wed, 16 Dec 2009 18:04:32 +0100
Committer: Ingo Molnar <mingo@...e.hu>
CommitDate: Wed, 16 Dec 2009 19:01:53 +0100
sched: Fix set_cpu_active() in cpu_down()
Sachin found cpu hotplug test failures on powerpc, which made
the kernel hang on his POWER box.
The problem is that we fail to re-activate a cpu when a
hot-unplug fails. Fix this by moving the de-activation into
_cpu_down after doing the initial checks.
Remove the synchronize_sched() calls and rely on those implied
by rebuilding the sched domains using the new mask.
Reported-by: Sachin Sant <sachinp@...ibm.com>
Signed-off-by: Xiaotian Feng <dfeng@...hat.com>
Tested-by: Sachin Sant <sachinp@...ibm.com>
Signed-off-by: Peter Zijlstra <a.p.zijlstra@...llo.nl>
Cc: Mike Galbraith <efault@....de>
LKML-Reference: <20091216170517.500272612@...llo.nl>
Signed-off-by: Ingo Molnar <mingo@...e.hu>
---
kernel/cpu.c | 24 +++---------------------
1 files changed, 3 insertions(+), 21 deletions(-)
diff --git a/kernel/cpu.c b/kernel/cpu.c
index 291ac58..1c8ddd6 100644
--- a/kernel/cpu.c
+++ b/kernel/cpu.c
@@ -209,6 +209,7 @@ static int __ref _cpu_down(unsigned int cpu, int tasks_frozen)
return -ENOMEM;
cpu_hotplug_begin();
+ set_cpu_active(cpu, false);
err = __raw_notifier_call_chain(&cpu_chain, CPU_DOWN_PREPARE | mod,
hcpu, -1, &nr_calls);
if (err == NOTIFY_BAD) {
@@ -280,18 +281,6 @@ int __ref cpu_down(unsigned int cpu)
goto out;
}
- set_cpu_active(cpu, false);
-
- /*
- * Make sure the all cpus did the reschedule and are not
- * using stale version of the cpu_active_mask.
- * This is not strictly necessary becuase stop_machine()
- * that we run down the line already provides the required
- * synchronization. But it's really a side effect and we do not
- * want to depend on the innards of the stop_machine here.
- */
- synchronize_sched();
-
err = _cpu_down(cpu, 0);
out:
@@ -382,19 +371,12 @@ int disable_nonboot_cpus(void)
return error;
cpu_maps_update_begin();
first_cpu = cpumask_first(cpu_online_mask);
- /* We take down all of the non-boot CPUs in one shot to avoid races
+ /*
+ * We take down all of the non-boot CPUs in one shot to avoid races
* with the userspace trying to use the CPU hotplug at the same time
*/
cpumask_clear(frozen_cpus);
- for_each_online_cpu(cpu) {
- if (cpu == first_cpu)
- continue;
- set_cpu_active(cpu, false);
- }
-
- synchronize_sched();
-
printk("Disabling non-boot CPUs ...\n");
for_each_online_cpu(cpu) {
if (cpu == first_cpu)
--
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