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authorOleg Nesterov <oleg@tv-sign.ru>2008-07-25 01:47:38 -0700
committerLinus Torvalds <torvalds@linux-foundation.org>2008-07-25 10:53:39 -0700
commit246bb0b1deb29726990620d8b5e55ca29f331362 (patch)
tree5173b9e0c1d18934a8b2693c690a7162acb1bca8 /kernel
parent7b34e4283c685f5cc6ba6d30e939906eee0d4bcf (diff)
downloadlinux-2.6.34-ux500-246bb0b1deb29726990620d8b5e55ca29f331362.tar.gz
kill PF_BORROWED_MM in favour of PF_KTHREAD
Kill PF_BORROWED_MM. Change use_mm/unuse_mm to not play with ->flags, and do s/PF_BORROWED_MM/PF_KTHREAD/ for a couple of other users. No functional changes yet. But this allows us to do further fixes/cleanups. oom_kill/ptrace/etc often check "p->mm != NULL" to filter out the kthreads, this is wrong because of use_mm(). The problem with PF_BORROWED_MM is that we need task_lock() to avoid races. With this patch we can check PF_KTHREAD directly, or use a simple lockless helper: /* The result must not be dereferenced !!! */ struct mm_struct *__get_task_mm(struct task_struct *tsk) { if (tsk->flags & PF_KTHREAD) return NULL; return tsk->mm; } Note also ecard_task(). It runs with ->mm != NULL, but it's the kernel thread without PF_BORROWED_MM. Signed-off-by: Oleg Nesterov <oleg@tv-sign.ru> Cc: Roland McGrath <roland@redhat.com> Signed-off-by: Andrew Morton <akpm@linux-foundation.org> Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>
Diffstat (limited to 'kernel')
-rw-r--r--kernel/fork.c4
1 files changed, 2 insertions, 2 deletions
diff --git a/kernel/fork.c b/kernel/fork.c
index 228f80c9155..eeaec6893b0 100644
--- a/kernel/fork.c
+++ b/kernel/fork.c
@@ -474,7 +474,7 @@ EXPORT_SYMBOL_GPL(mmput);
/**
* get_task_mm - acquire a reference to the task's mm
*
- * Returns %NULL if the task has no mm. Checks PF_BORROWED_MM (meaning
+ * Returns %NULL if the task has no mm. Checks PF_KTHREAD (meaning
* this kernel workthread has transiently adopted a user mm with use_mm,
* to do its AIO) is not set and if so returns a reference to it, after
* bumping up the use count. User must release the mm via mmput()
@@ -487,7 +487,7 @@ struct mm_struct *get_task_mm(struct task_struct *task)
task_lock(task);
mm = task->mm;
if (mm) {
- if (task->flags & PF_BORROWED_MM)
+ if (task->flags & PF_KTHREAD)
mm = NULL;
else
atomic_inc(&mm->mm_users);