powerpc: Fix deadlock in icswx code
The icswx code introduced an A-B B-A deadlock:
CPU0 CPU1
---- ----
lock(&anon_vma->mutex);
lock(&mm->mmap_sem);
lock(&anon_vma->mutex);
lock(&mm->mmap_sem);
Instead of using the mmap_sem to keep mm_users constant, take the
page table spinlock.
Signed-off-by: Anton Blanchard <anton@samba.org>
Cc: <stable@kernel.org>
Signed-off-by: Benjamin Herrenschmidt <benh@kernel.crashing.org>
diff --git a/arch/powerpc/mm/mmu_context_hash64.c b/arch/powerpc/mm/mmu_context_hash64.c
index 3bafc3d..4ff587e 100644
--- a/arch/powerpc/mm/mmu_context_hash64.c
+++ b/arch/powerpc/mm/mmu_context_hash64.c
@@ -136,8 +136,8 @@
if (!mm || !acop)
return -EINVAL;
- /* We need to make sure mm_users doesn't change */
- down_read(&mm->mmap_sem);
+ /* The page_table_lock ensures mm_users won't change under us */
+ spin_lock(&mm->page_table_lock);
spin_lock(mm->context.cop_lockp);
if (mm->context.cop_pid == COP_PID_NONE) {
@@ -164,7 +164,7 @@
out:
spin_unlock(mm->context.cop_lockp);
- up_read(&mm->mmap_sem);
+ spin_unlock(&mm->page_table_lock);
return ret;
}
@@ -185,8 +185,8 @@
if (WARN_ON_ONCE(!mm))
return;
- /* We need to make sure mm_users doesn't change */
- down_read(&mm->mmap_sem);
+ /* The page_table_lock ensures mm_users won't change under us */
+ spin_lock(&mm->page_table_lock);
spin_lock(mm->context.cop_lockp);
mm->context.acop &= ~acop;
@@ -213,7 +213,7 @@
}
spin_unlock(mm->context.cop_lockp);
- up_read(&mm->mmap_sem);
+ spin_unlock(&mm->page_table_lock);
}
EXPORT_SYMBOL_GPL(drop_cop);