Thunderbird and the nasty – not responding – issue

Recently, I ran into an extremely frustrating issue with Thunderbird. After booting up my Mac, I couldn’t get it to open right after logging in. I was forced to wait about 5 to 10 minutes for it to run properly; whenever I tried opening it immediately after login, it became completely unresponsive.

In Activity Monitor, it was marked as ‘Not Responding’

and generating a spindump report indicated an issue with fonts.

...
...
  115   mach_msg2_trap + 8 (libsystem_kernel.dylib + 3124) [0x1841d1c34]
    ... (blocked by turnstile waiting for fontd [678] thread 0x36075 after 2 hops)
    ... (runnable)
    ... (blocked by turnstile waiting for fontd [678] thread 0x36075 after 4 hops)
    ... (blocked by turnstile waiting for fontd [678] thread 0x36075 after 3 hops)
    ... (running)

The funny thing was that running it a few minutes after logging in didn’t trigger the issue. All signs pointed to a font related problem, so I tried clearing the font cache.

sudo atsutil databases -remove
atsutil databases -removeUser
sudo reboot

I checked all the fonts for corruption, but nothing resolved the issue.

Eventually, I recalled that another app manages fonts: Adobe Creative Cloud. It was a wild guess, but I decided to test it. I turned off all Creative Cloud services, and that was the fix – everything now works as expected. However, there is still one catch: if I start Creative Cloud manually and open Thunderbird right after, Thunderbird goes back into that unresponsive state. It seems like the two apps are conflicting over font access.

I have created dedicated issue here as well. It might happen there is something else triggering the problem: https://bugzilla.mozilla.org/show_bug.cgi?id=2060146