diff options
| -rw-r--r-- | fs/proc/task_mmu.c | 33 |
1 files changed, 9 insertions, 24 deletions
diff --git a/fs/proc/task_mmu.c b/fs/proc/task_mmu.c index adddf697c4ea..1acec26a3758 100644 --- a/fs/proc/task_mmu.c +++ b/fs/proc/task_mmu.c @@ -87,32 +87,14 @@ unsigned long task_statm(struct mm_struct *mm, #ifdef CONFIG_NUMA /* - * These functions are for numa_maps but called in generic **maps seq_file - * ->start(), ->stop() ops. - * - * numa_maps scans all vmas under mmap_sem and checks their mempolicy. - * Each mempolicy object is controlled by reference counting. The problem here - * is how to avoid accessing dead mempolicy object. - * - * Because we're holding mmap_sem while reading seq_file, it's safe to access - * each vma's mempolicy, no vma objects will never drop refs to mempolicy. - * - * A task's mempolicy (task->mempolicy) has different behavior. task->mempolicy - * is set and replaced under mmap_sem but unrefed and cleared under task_lock(). - * So, without task_lock(), we cannot trust get_vma_policy() because we cannot - * gurantee the task never exits under us. But taking task_lock() around - * get_vma_plicy() causes lock order problem. - * - * To access task->mempolicy without lock, we hold a reference count of an - * object pointed by task->mempolicy and remember it. This will guarantee - * that task->mempolicy points to an alive object or NULL in numa_maps accesses. + * Save get_task_policy() for show_numa_map(). */ static void hold_task_mempolicy(struct proc_maps_private *priv) { struct task_struct *task = priv->task; task_lock(task); - priv->task_mempolicy = task->mempolicy; + priv->task_mempolicy = get_task_policy(task); mpol_get(priv->task_mempolicy); task_unlock(task); } @@ -1431,7 +1413,6 @@ static int show_numa_map(struct seq_file *m, void *v, int is_pid) struct vm_area_struct *vma = v; struct numa_maps *md = &numa_priv->md; struct file *file = vma->vm_file; - struct task_struct *task = proc_priv->task; struct mm_struct *mm = vma->vm_mm; struct mm_walk walk = {}; struct mempolicy *pol; @@ -1451,9 +1432,13 @@ static int show_numa_map(struct seq_file *m, void *v, int is_pid) walk.private = md; walk.mm = mm; - pol = get_vma_policy(task, vma, vma->vm_start); - mpol_to_str(buffer, sizeof(buffer), pol); - mpol_cond_put(pol); + pol = __get_vma_policy(vma, vma->vm_start); + if (pol) { + mpol_to_str(buffer, sizeof(buffer), pol); + mpol_cond_put(pol); + } else { + mpol_to_str(buffer, sizeof(buffer), proc_priv->task_mempolicy); + } seq_printf(m, "%08lx %s", vma->vm_start, buffer); |