[Bug 241927] kernel crash in kern_cpuset_setdomain(CPU_LEVEL_CPUSET, CPU_WHICH_PID, -1, ...)

[bugzilla-noreply at freebsd.org]

https://bugs.freebsd.org/bugzilla/show_bug.cgi?id=241927

            Bug ID: 241927
           Summary: kernel crash in
                    kern_cpuset_setdomain(CPU_LEVEL_CPUSET, CPU_WHICH_PID,
                    -1, ...)
           Product: Base System
           Version: 12.0-RELEASE
          Hardware: Any
                OS: Any
            Status: New
          Severity: Affects Only Me
          Priority: ---
         Component: kern
          Assignee: bugs at FreeBSD.org
          Reporter: bgoglin at free.fr

Created attachment 209111
  --> https://bugs.freebsd.org/bugzilla/attachment.cgi?id=209111&action=edit
screenshot of the backtrace of the crash

Hello

While adding FreeBSD NUMA support in hwloc, we found a reproducible way to
crash the kernel. Just call cpuset_setdomain(CPU_LEVEL_CPUSET, CPU_WHICH_PID,
-1, ...).

Here's the minimalistic userland program to reproduce:

#include <sys/types.h>
#include <sys/sysctl.h>
#include <sys/param.h>
#include <sys/cpuset.h>
#include <sys/domainset.h>

int main()
{
  domainset_t mask;
  DOMAINSET_ZERO(&mask);
  DOMAINSET_SET(0, &mask);
  cpuset_setdomain(CPU_LEVEL_CPUSET, CPU_WHICH_PID, -1, sizeof(mask),
&mask, DOMAINSET_POLICY_PREFER);
}

I don't understand what this call is supposed to do, we actually wanted to use
CPU_LEVEL_WHICH instead of CPU_LEVEL_CPUSET :)

We were running this inside a KVM VM with 4 NUMA domains but the crash also
occurs without multiple NUMA domains.

I am attaching a screenshot of the backtrace after the crash. I don't know how
to debug more.

Brice

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