>
> I also don't think the hack is that bad. All it's doing is taking a
> copy of the process's VM decription so that it knows that
> nobody is going to modify it whilst a coredump is in progress.
You break the locking scheme of the mm structure.
Right now the rules are
1 get a mm_struct pointer by whatever means (walk the process list and
read task->mm, walk the mm_list)
2 increase mm_users
3 release the spinlock you acquired for 1
4 you can do with the result what you want.
With your patch applied, we would have to restrict rule 4 - at least
modifying the vma list is not possible anymore, probably further
changes.
AFAIK right now no external mm_struct user modifies the vma list, but it
could be a problem in the future.
>
> However, if you don't like that, how about just changing the lock on
> mm_struct to a special mm_struct-only type lock that has a
> recursive lock operation for use by the pagefault handler (and
> _only_ the pagefault handler)? I've attached a patch to do just that.
> This introduces five operations:
Does that solve the latency problem? That problem is pagefaults vs.
another operation.
--
Manfred
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This archive was generated by hypermail 2b29 : Sun Sep 23 2001 - 21:00:35 EST