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authorBenjamin Herrenschmidt <benh@kernel.crashing.org>2009-06-02 18:53:37 +0000
committerBenjamin Herrenschmidt <benh@kernel.crashing.org>2009-06-09 16:43:04 +1000
commitb46b6942b39e577fe3ef1af928cd927864011247 (patch)
tree8eea7316ac79fae34ee7fdbccc580fbac1589ff3 /arch/powerpc/mm
parent3035c8634f0538a0c6946e3191bb6c9284b63798 (diff)
powerpc/mm: Fix a AB->BA deadlock scenario with nohash MMU context lock
The MMU context_lock can be taken from switch_mm() while the rq->lock is held. The rq->lock can also be taken from interrupts, thus if we get interrupted in destroy_context() with the context lock held and that interrupt tries to take the rq->lock, there's a possible deadlock scenario with another CPU having the rq->lock and calling switch_mm() which takes our context lock. The fix is to always ensure interrupts are off when taking our context lock. The switch_mm() path is already good so this fixes the destroy_context() path. While at it, turn the context lock into a new style spinlock. Signed-off-by: Benjamin Herrenschmidt <benh@kernel.crashing.org>
Diffstat (limited to 'arch/powerpc/mm')
-rw-r--r--arch/powerpc/mm/mmu_context_nohash.c7
1 files changed, 4 insertions, 3 deletions
diff --git a/arch/powerpc/mm/mmu_context_nohash.c b/arch/powerpc/mm/mmu_context_nohash.c
index c42858780cb..8343986809c 100644
--- a/arch/powerpc/mm/mmu_context_nohash.c
+++ b/arch/powerpc/mm/mmu_context_nohash.c
@@ -46,7 +46,7 @@ static unsigned int next_context, nr_free_contexts;
static unsigned long *context_map;
static unsigned long *stale_map[NR_CPUS];
static struct mm_struct **context_mm;
-static spinlock_t context_lock = SPIN_LOCK_UNLOCKED;
+static DEFINE_SPINLOCK(context_lock);
#define CTX_MAP_SIZE \
(sizeof(unsigned long) * (last_context / BITS_PER_LONG + 1))
@@ -276,6 +276,7 @@ int init_new_context(struct task_struct *t, struct mm_struct *mm)
*/
void destroy_context(struct mm_struct *mm)
{
+ unsigned long flags;
unsigned int id;
if (mm->context.id == MMU_NO_CONTEXT)
@@ -283,7 +284,7 @@ void destroy_context(struct mm_struct *mm)
WARN_ON(mm->context.active != 0);
- spin_lock(&context_lock);
+ spin_lock_irqsave(&context_lock, flags);
id = mm->context.id;
if (id != MMU_NO_CONTEXT) {
__clear_bit(id, context_map);
@@ -294,7 +295,7 @@ void destroy_context(struct mm_struct *mm)
context_mm[id] = NULL;
nr_free_contexts++;
}
- spin_unlock(&context_lock);
+ spin_unlock_irqrestore(&context_lock, flags);
}
#ifdef CONFIG_SMP