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tools/uma/smrstress: fix kthread exit

Authored by kib on Jul 30 2022, 7:01 PM.


By convention, kernel threads must call kthread_exit() instead of
blindly returning from the thread function.  We have some safety measure
in fork_exit(), which checks for the P_KPROC p_flag and does
kthread_exit() for kernel thread that forgot to do it itself.

But this workaround only works for kernel threads belonging to the
kernel process.  If a kernel thread is attached to the normal process
with live userspace, and does not call kthread_exit(), then the
workaround is not activated, and for amd64 at least, the return from the
thread function/fork_exit() results in the return to userspace with the
copy of frame from the thread that did kthread_add().

Practically for smrstress, this destroys the user stack of the still
active frame.

Fix it by adding kthread_exit() to the thread function.

Reported by:    pho

Diff Detail

rG FreeBSD src repository
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Event Timeline

kib requested review of this revision.Jul 30 2022, 7:01 PM
kib added a reviewer: markj.
This revision is now accepted and ready to land.Jul 30 2022, 8:59 PM
This revision was automatically updated to reflect the committed changes.