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>
static unsigned long *context_map;
static unsigned long *stale_map[NR_CPUS];
static struct mm_struct **context_mm;
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))
#define CTX_MAP_SIZE \
(sizeof(unsigned long) * (last_context / BITS_PER_LONG + 1))
*/
void destroy_context(struct mm_struct *mm)
{
*/
void destroy_context(struct mm_struct *mm)
{
unsigned int id;
if (mm->context.id == MMU_NO_CONTEXT)
unsigned int id;
if (mm->context.id == MMU_NO_CONTEXT)
WARN_ON(mm->context.active != 0);
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);
id = mm->context.id;
if (id != MMU_NO_CONTEXT) {
__clear_bit(id, context_map);
context_mm[id] = NULL;
nr_free_contexts++;
}
context_mm[id] = NULL;
nr_free_contexts++;
}
- spin_unlock(&context_lock);
+ spin_unlock_irqrestore(&context_lock, flags);