A customer of my Safari app extension is reporting a strange interaction with a 3rd party content blocker that causes Safari to hang, apparently in code signing. Spindumps of Safari show this:
Dispatch Thread Soft Limit Reached: 80 (too many dispatch threads blocked in synchronous operations)
Each spindump has over 20 DispatchQueue "Content Blocker Containing App Validation Queue"
In one spindump, it seems to be triggered by this:
-[WBSExtensionsController _extensionDiscoveryHasNewResults:] + 244 (SafariSharedUI + 149396)
In another:
__114-[WBSExtensionsController(SafariExtras) safari_validateContainingAppOfExtensionIfNecessary:attemptRetryOnFailure:]_block_invoke.44 + 52 (Safari + 5305260)
I can't reproduce the issue, however, so I'm baffled. The actual code signature of the app, which comes from the Mac App Store, appears to be fine, as verified with the codesign command-line utility.