After an upgrade of `xdg-desktop-portal/bullseye-backports` (which
needrestart didn't detect should be restarted, BTW:

tconnors    4388  0.0  0.0 617848  5372 ?        Sl    2021   2:14 /usr/libexec/xdg-desktop-portal
tconnors    4396  0.0  0.0 602912  2396 ?        Sl    2021   0:31 /usr/libexec/xdg-document-portal
root        4405  0.0  0.0   2572  1684 ?        Ss    2021   0:00  \_ fusermount -o rw,nosuid,nodev,fsname=portal,auto_unmount,subtype=portal -- /run/user/738/doc
tconnors    4411  0.0  0.0 529116 27656 ?        Sl    2021   8:13 /usr/libexec/xdg-desktop-portal-gtk

)

I was wondering why needrestart was taking even longer than usual.  So
I ran a few 'ps axfu' and discovered it was continually restarting
dpkg-query --search /bin/dash over and over again:

root     1130884  1.3  0.3 137036 123668 pts/125 S+   12:41   0:04          |       |                   \_ apt install xdg-desktop-portal/bullseye-backports
root     1131701  0.0  0.0 137036 32332 pts/125  S+   12:41   0:00          |       |                       \_ apt install xdg-desktop-portal/bullseye-backports
root     1141619  0.0  0.0   2424   596 pts/125  S+   12:41   0:00          |       |                           \_ sh -c test -x /usr/lib/needrestart/apt-pinvoke && /usr/lib/needrestart/apt-pinvoke || true
root     1141622  0.3  0.0  29212 23020 pts/125  S+   12:41   0:01          |       |                               \_ /usr/bin/perl -w /usr/share/debconf/frontend /usr/sbin/needrestart
root     1141782 14.3  0.2  83300 77220 pts/125  S+   12:42   0:45          |       |                                   \_ /usr/bin/perl /usr/sbin/needrestart
root     1152868  1.0  0.0  12052  6076 pts/125  S+   12:47   0:00          |       |                                       \_ /usr/bin/perl /etc/needrestart/hook.d/10-dpkg /bin/dash
root     1152870 99.0  0.3 134264 129920 pts/125 R+   12:47   0:00          |       |                                           \_ dpkg-query --search /bin/dash

With /etc/needrestart/hook.d/10-dpkg and dpkg-query --search /bin/dash
constantly recycling PIDs (but /usr/sbin/needrestart remaining at the
root of the process tree the whole time).

After a while, it finally moved onto /bin/bash, and then eventually
finished.  Since every time I looked, it was executing `dpkg-query
--search`, which takes 3 seconds when the filesystem cache is warm on
my system, it seems those results should be cached in the
/usr/sbin/needrestart process and 10-dpkg hook not asked to keep
reprocessing the same file, since they're obviously not able to change
when you're at the final step of a dpkg run with the dpkg lock held.