[PATCH 3.13.y-ckt 141/156] sparc32: destroy_context() and switch_mm() needs to disable interrupts.

From: Kamal Mostafa
Date: Tue Apr 07 2015 - 18:59:31 EST

3.13.11-ckt19 -stable review patch. If anyone has any objections, please let me know.


From: Andreas Larsson <andreas@xxxxxxxxxxx>

[ Upstream commit 66d0f7ec9f1038452178b1993fc07fd96d30fd38 ]

Load balancing can be triggered in the critical sections protected by
srmmu_context_spinlock in destroy_context() and switch_mm() and can hang
the cpu waiting for the rq lock of another cpu that in turn has called
switch_mm hangning on srmmu_context_spinlock leading to deadlock.

So, disable interrupt while taking srmmu_context_spinlock in
destroy_context() and switch_mm() so we don't deadlock.

See also commit 77b838fa1ef0 ("[SPARC64]: destroy_context() needs to disable

Signed-off-by: Andreas Larsson <andreas@xxxxxxxxxxx>
Signed-off-by: David S. Miller <davem@xxxxxxxxxxxxx>
Signed-off-by: Kamal Mostafa <kamal@xxxxxxxxxxxxx>
arch/sparc/mm/srmmu.c | 11 +++++++----
1 file changed, 7 insertions(+), 4 deletions(-)

diff --git a/arch/sparc/mm/srmmu.c b/arch/sparc/mm/srmmu.c
index 869023a..769bf7f 100644
--- a/arch/sparc/mm/srmmu.c
+++ b/arch/sparc/mm/srmmu.c
@@ -458,10 +458,12 @@ static void __init sparc_context_init(int numctx)
void switch_mm(struct mm_struct *old_mm, struct mm_struct *mm,
struct task_struct *tsk)
+ unsigned long flags;
if (mm->context == NO_CONTEXT) {
- spin_lock(&srmmu_context_spinlock);
+ spin_lock_irqsave(&srmmu_context_spinlock, flags);
alloc_context(old_mm, mm);
- spin_unlock(&srmmu_context_spinlock);
+ spin_unlock_irqrestore(&srmmu_context_spinlock, flags);
srmmu_ctxd_set(&srmmu_context_table[mm->context], mm->pgd);

@@ -986,14 +988,15 @@ int init_new_context(struct task_struct *tsk, struct mm_struct *mm)

void destroy_context(struct mm_struct *mm)
+ unsigned long flags;

if (mm->context != NO_CONTEXT) {
srmmu_ctxd_set(&srmmu_context_table[mm->context], srmmu_swapper_pg_dir);
- spin_lock(&srmmu_context_spinlock);
+ spin_lock_irqsave(&srmmu_context_spinlock, flags);
- spin_unlock(&srmmu_context_spinlock);
+ spin_unlock_irqrestore(&srmmu_context_spinlock, flags);
mm->context = NO_CONTEXT;

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