https://bugs.freebsd.org/bugzilla/show_bug.cgi?id=222242
Bug ID: 222242
Summary: [patch] allow masks smaller than cpuset_t, if large
enough for mp_maxid
Product: Base System
Version: 11.1-RELEASE
Hardware: amd64
OS: Any
Status: New
Keywords: patch
Severity: Affects Some People
Priority: ---
Component: kern
Assignee: freebsd-bugs@FreeBSD.org
Reporter: free...@ruka.org
Keywords: patch
Created attachment 186278
--> https://bugs.freebsd.org/bugzilla/attachment.cgi?id=186278&action=edit
patch to check that mask is actually too small, not just smaller than the
kernel compiled type
As mentioned in Bug 200802, increasing MAXCPUS breaks compatibility for
software setting cpu affinity compiled on earlier versions of FreeBSD.
With this patch, the calls will only fail with ERANGE if the mask size is
actually too small.
In case of running old binaries on new systems with more cpus than fit in the
mask, that's still not going to work with this patch.
In response to a comment on that bug:
https://bugs.freebsd.org/bugzilla/show_bug.cgi?id=200802#c4
> Shouldn't cpuset users be querying the cpuset size from sysctl and using that
> as their allocation base?
Possibly, but then the calling code wouldn't be able to use cpuset_t types, or
CPU_SET macros.
Some updates of documentation would be required too, as the documentation
currently says when using a too small mask, get returns an error, and set runs
without error (which doesn't appear to be correct).
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