diff options
| author | Benjamin Herrenschmidt <benh@kernel.crashing.org> | 2009-06-02 18:53:37 +0000 |
|---|---|---|
| committer | Benjamin Herrenschmidt <benh@kernel.crashing.org> | 2009-06-09 16:43:04 +1000 |
| commit | b46b6942b39e577fe3ef1af928cd927864011247 (patch) | |
| tree | 8eea7316ac79fae34ee7fdbccc580fbac1589ff3 | |
| parent | 3035c8634f0538a0c6946e3191bb6c9284b63798 (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>
| -rw-r--r-- | arch/powerpc/mm/mmu_context_nohash.c | 7 |
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 |