Re: kern/56900: panic in uvm_map_findspace

[mlelstv%serpens.de@localhost (Michael van Elst)]

The following reply was made to PR kern/56900; it has been noted by GNATS.

From: mlelstv%serpens.de@localhost (Michael van Elst)
To: gnats-bugs%netbsd.org@localhost
Cc: 
Subject: Re: kern/56900: panic in uvm_map_findspace
Date: Mon, 27 Jun 2022 06:05:16 -0000 (UTC)

 riastradh%NetBSD.org@localhost (Taylor R Campbell) writes:
 
 > Using compat_43_ommap instead of mmap is probably not particularly
 > significant here; most likely there is just some edge case in the
 > uvm_map_findspace logic that we're missing -- really, the whole of
 > uvm_map_findspace is a twisty maze of sharp edge cases waiting to
 > impale unwary passersby, and the whole thing should be reorganized
 > more coherently with assertions of invariants.
 
 The "invariants" really don't make sense. These conditions just check
 for a heuristic that cannot be enforced without producing the issue
 that you try to fix.
 
 The code can be simplified very easily, but you have to define
 the "bottom up" strategy. My guess is that there is none, it
 just happens to work by chance.