Messages in this thread |  | | Date | Sun, 9 Sep 2001 05:50:38 +0200 | From | Andrea Arcangeli <> | Subject | Re: expand_stack fix [was Re: 2.4.9aa3] |
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On Sat, Sep 08, 2001 at 11:23:38PM -0500, Jeff Dike wrote: > andrea@suse.de said: > > My fix for the race doesn't drop the usability of GROWSDOWN that could > > otherwise break userspace programs. I guess at least uml uses > > growsdown vma file backed. Jeff? > > No. In neither the host kernel or UML is there a vma that's file backed and > growsdown. > > UML process stacks are marked growsdown in UML and are file backed on the host, > but that's not the same thing.
ok, so I guess you're doing the growsdown by hand in the uml sigsegv handler.
So it's probably fine to allow GROWSDOWN only on anon vmas per Linus's suggestion. I can attempt to change the race fix that way.
However about last Linus's suggestion it's not obvious to me that dropping GROWSDOWN/UP completly and forcing a fixed virtual size of the stack [modulo rlimit of course] is a good idea, because:
1) on 32bit platforms having big vma for the stack means reducing the space for the dynamic mappings 2) I love not to have a virtual stack limit for software making use of aggressive recursion.
The gap logic is very simple too.
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