Re: [RFH] gpg --import entropy while running tests

On Wed, Dec 28, 2016 at 02:23:03AM -0500, Jeff King wrote:

That's a lot of time not using any CPU. What's going on? Running with
"sh -x" shows that we spend most of the time in this line from
lib-gpg.sh:

  gpg --homedir "${GNUPGHOME}" 2>/dev/null --import \
	  "$TEST_DIRECTORY"/lib-gpg/keyring.gpg

And running gpg with "--debug-level guru" shows that we are blocking
while waiting for entropy. Has anybody else seen this? I feel like I
noticed it starting a few weeks ago, and indeed dropping back to gpg
2.0.26 (from 2.1.17) makes the problem go away.

Is it a bug in gpg (oddly, the kernel reports lots of entropy available,
and generating the signatures themselves is quite fast)? Or is the new
version doing something special in the import process that we need to
work around or disable?

Answering my own question (somewhat): this is bisectable in the gnupg
repository, and it turns out to be caused by their 4473db1ef (agent:
Kludge to mitigate blocking calls in Libgcrypt., 2016-11-11), which
introduces a 100ms sleep (yuck) that is presumably triggering way more
than it needs to. More details at:

  https://git.gnupg.org/cgi-bin/gitweb.cgi?p=gnupg.git;a=commit;h=4473db1ef24031ff4e26c9a9de95dbe898ed2b97

So this does seem like a gpg bug.

-Peff