linux-kernel - [PATCH 1/5] metag: use clear_tasks_mm

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Date:	Mon, 1 Jul 2013 17:04:15 +0100
From:	James Hogan <james.hogan@...tec.com>
To:	<linux-kernel@...r.kernel.org>
CC:	Thomas Gleixner <tglx@...utronix.de>,
	James Hogan <james.hogan@...tec.com>,
	"Srivatsa S. Bhat" <srivatsa.bhat@...ux.vnet.ibm.com>,
	Oleg Nesterov <oleg@...hat.com>,
	"Anton Vorontsov" <anton.vorontsov@...aro.org>
Subject: [PATCH 1/5] metag: use clear_tasks_mm_cpumask()

Checking for process->mm is not enough because process' main thread may
exit or detach its mm via use_mm(), but other threads may still have a
valid mm.

To fix this we would need to use find_lock_task_mm(), which would walk
up all threads and returns an appropriate task (with task lock held).

clear_tasks_mm_cpumask() was introduced in v3.5-rc1 to fix this issue,
so let's use it for metag too.

Signed-off-by: James Hogan <james.hogan@...tec.com>
Cc: "Srivatsa S. Bhat" <srivatsa.bhat@...ux.vnet.ibm.com>
Cc: Thomas Gleixner <tglx@...utronix.de>
Cc: Oleg Nesterov <oleg@...hat.com>
Cc: Anton Vorontsov <anton.vorontsov@...aro.org>
---
 arch/metag/kernel/smp.c | 8 +-------
 1 file changed, 1 insertion(+), 7 deletions(-)

diff --git a/arch/metag/kernel/smp.c b/arch/metag/kernel/smp.c
index 86fdda4..b813515 100644
--- a/arch/metag/kernel/smp.c
+++ b/arch/metag/kernel/smp.c
@@ -276,7 +276,6 @@ static DECLARE_COMPLETION(cpu_killed);
 int __cpuexit __cpu_disable(void)
 {
 	unsigned int cpu = smp_processor_id();
-	struct task_struct *p;
 
 	/*
 	 * Take this CPU offline.  Once we clear this, we can't return,
@@ -296,12 +295,7 @@ int __cpuexit __cpu_disable(void)
 	flush_cache_all();
 	local_flush_tlb_all();
 
-	read_lock(&tasklist_lock);
-	for_each_process(p) {
-		if (p->mm)
-			cpumask_clear_cpu(cpu, mm_cpumask(p->mm));
-	}
-	read_unlock(&tasklist_lock);
+	clear_tasks_mm_cpumask(cpu);
 
 	return 0;
 }
-- 
1.8.1.2


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