Messages in this thread |  | | Date | Thu, 20 Sep 2001 10:09:40 +0200 | From | Andrea Arcangeli <> | Subject | Re: Deadlock on the mm->mmap_sem |
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On Thu, Sep 20, 2001 at 09:01:13AM +0100, David Howells wrote: > > Andrea Arcangeli <andrea@suse.de> wrote: > > the process doesn't need to lock multiple mm_structs at the same time. > > fork, ptrace, /proc/pid/mem, /proc/pid/maps > > All have to be able to lock two process's mm_structs simultaneously, even if > it's indirectly through copy_to_user() or copy_from_user().
ptrace doesn't use down_read_recursive, nor /proc/<>/mem, nor fork.
for /proc/<pid>/maps this check takes care of it of course (or it could get unfair again: only when we're faulting on our vm we're allowed to go through):
if (task == current) down_read_recursive(&mm->mmap_sem, ¤t->mm_recursor); else down_read(&mm->mmap_sem);
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