As a background, I mentioned that we occasionally have these scary crashes while running our iOS tests that either reboot your Mac or crash the user process out to the login screen.
Yesterday, I noticed that I could not run our tests at all without crashing around a certain area and on 3 different Macs, all with 24 GB or more of RAM. My speculation that it, might be related to mach ports was entirely correct as after 8 crashes, some debug logs finally appeared - but not all the time. Our iOS UI tests are run by KIF which uses XCTest as its foundation. When running these 280+ UI automation scripts in the Simulator, the amount of ports used by Xcode increased rapidly as the tests ran for 30 mins and the WindowServer process appeared to have about 20,000 more Mach ports allocated than Xcode over that time. Right before the crash happened, the WindowServer had allocated over 256,000 ports and Xcode was just behind by a few thousand. Then, all operation pauses for a few seconds, the displays go black, and a few seconds later, the user login screen appears as the previous user session crashed out. What happened is that Xcode asked for more ports and asked the WindowServer to allocate more ports and the WindowServer asked the GPU driver for more ports and thread com.apple.SkyLight.mtl_submit to crash with either a SIGSEV or SIGILL. Either the WindowServer or the Skylight framework for MetalDevice and caused a GPU restart. The OS then crashed the user session out to the login screen. Now, the question. Why the hell is XCTest causing Xcode to request so many Mach ports and never release them until the app is quit or the system crashes? I tested this last night outside of our app with XCTest and KIF simply going back and forth between two screens in an iOS app several thousand times In the Simulator. The mach ports of both Xcode and the WindowServer go up and are not released until the app quits, but not nearly as fast as in our tests. Is this a mach port leak in XCTest? Does anyone know the details on the guts of this? Thanks a lot and I hope this helps someone else. Alex Zavatone Sent from my iThing. _______________________________________________ Cocoa-dev mailing list (Cocoa-dev@lists.apple.com) Please do not post admin requests or moderator comments to the list. Contact the moderators at cocoa-dev-admins(at)lists.apple.com Help/Unsubscribe/Update your Subscription: https://lists.apple.com/mailman/options/cocoa-dev/archive%40mail-archive.com This email sent to arch...@mail-archive.com
