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authorOleg Nesterov <oleg@tv-sign.ru>2008-07-25 04:47:38 -0400
committerLinus Torvalds <torvalds@linux-foundation.org>2008-07-25 13:53:39 -0400
commit246bb0b1deb29726990620d8b5e55ca29f331362 (patch)
tree5173b9e0c1d18934a8b2693c690a7162acb1bca8 /fs
parent7b34e4283c685f5cc6ba6d30e939906eee0d4bcf (diff)
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 'fs')
-rw-r--r--fs/aio.c2
1 files changed, 0 insertions, 2 deletions
diff --git a/fs/aio.c b/fs/aio.c
index 0fb3117ddd93..0051fd94b44e 100644
--- a/fs/aio.c
+++ b/fs/aio.c
@@ -586,7 +586,6 @@ static void use_mm(struct mm_struct *mm)
586 struct task_struct *tsk = current; 586 struct task_struct *tsk = current;
587 587
588 task_lock(tsk); 588 task_lock(tsk);
589 tsk->flags |= PF_BORROWED_MM;
590 active_mm = tsk->active_mm; 589 active_mm = tsk->active_mm;
591 atomic_inc(&mm->mm_count); 590 atomic_inc(&mm->mm_count);
592 tsk->mm = mm; 591 tsk->mm = mm;
@@ -610,7 +609,6 @@ static void unuse_mm(struct mm_struct *mm)
610 struct task_struct *tsk = current; 609 struct task_struct *tsk = current;
611 610
612 task_lock(tsk); 611 task_lock(tsk);
613 tsk->flags &= ~PF_BORROWED_MM;
614 tsk->mm = NULL; 612 tsk->mm = NULL;
615 /* active_mm is still 'mm' */ 613 /* active_mm is still 'mm' */
616 enter_lazy_tlb(mm, tsk); 614 enter_lazy_tlb(mm, tsk);