With today's Nightly, as soon as I open a particular second profile the browser hangs within about 5 seconds. Generally the compositor process appears to be working as normal (certain animations continue running). On a couple of occasions the Ubuntu crash report popped up and showed a stack with something like IPC channel error at the top (I wish I could find the actual error -- there's nothing in Firefox's crash logs I can find). On IRC, Mythmon reported seeing something similar except that he is not running two profiles, just two windows and it is happening within a few minutes (as opposed to 5 seconds). He comments: "in the terminal I saw an error about IPC, but I'm not sure if it is related: [Parent 29572, Gecko_IOThread] WARNING: pipe error (175): Connection reset by peer: file /builds/worker/workspace/build/src/ipc/chromium/src/chrome/common/ipc_channel_posix.cc, line 363" Interestingly, while Ubuntu is showing the "Force Quit / Terminate" window various content processes in the other profile hang (and, again I suppose the compositor process is still responsive because I can scroll by dragging the scrollbar, but not by using the mousewheel). In my apport.log I get a bunch of content process crashes: ERROR: apport (pid 18950) Thu Oct 18 07:52:03 2018: called for pid 18911, signal 11, core limit 0, dump mode 1 ERROR: apport (pid 18950) Thu Oct 18 07:52:03 2018: executable: /opt/firefox/firefox-bin (command line "/opt/firefox/firefox-bin -contentproc -childID 5 -isForBrowser -prefsLen 6682 -prefMapSize 182495 -schedulerPrefs 0001,2 -parentBuildID 20181017101626 -greomni /opt/firefox/omni.ja -appomni /opt/firefox/browser/omni.ja -appdir /opt/firefox/browser 16390 true tab") ERROR: apport (pid 18950) Thu Oct 18 07:52:03 2018: debug: session gdbus call: (true,) ERROR: apport (pid 18950) Thu Oct 18 07:52:06 2018: wrote report /var/crash/_opt_firefox_firefox-bin.1000.crash ERROR: apport (pid 18948) Thu Oct 18 07:52:06 2018: called for pid 17466, signal 11, core limit 0, dump mode 1 ERROR: apport (pid 18948) Thu Oct 18 07:52:06 2018: executable: /opt/firefox/firefox-bin (command line "/opt/firefox/firefox-bin -contentproc -childID 3 -isForBrowser -prefsLen 5394 -prefMapSize 182495 -schedulerPrefs 0001,2 -parentBuildID 20181017101626 -greomni /opt/firefox/omni.ja -appomni /opt/firefox/browser/omni.ja -appdir /opt/firefox/browser 16390 true tab") ERROR: apport (pid 18948) Thu Oct 18 07:52:06 2018: debug: session gdbus call: (true,) ERROR: apport (pid 18948) Thu Oct 18 07:52:06 2018: apport: report /var/crash/_opt_firefox_firefox-bin.1000.crash already exists and unseen, doing nothing to avoid disk usage DoS ERROR: apport (pid 18952) Thu Oct 18 07:52:06 2018: called for pid 16520, signal 11, core limit 0, dump mode 1 ERROR: apport (pid 18952) Thu Oct 18 07:52:06 2018: executable: /opt/firefox/firefox-bin (command line "/opt/firefox/firefox-bin -contentproc -childID 1 -isForBrowser -prefsLen 1 -prefMapSize 182495 -schedulerPrefs 0001,2 -parentBuildID 20181017101626 -greomni /opt/firefox/omni.ja -appomni /opt/firefox/browser/omni.ja -appdir /opt/firefox/browser 16390 true tab") ERROR: apport (pid 18952) Thu Oct 18 07:52:06 2018: debug: session gdbus call: (true,)

Just running the hanging profile by itself, it also hangs. So it seems to be profile-specific. From the crash log: ProcVersionSignature: Ubuntu 4.15.0-36.39-generic 4.15.18 Registers: rax 0x7f20ef9ace6b 139779435581035 rbx 0x7f20fa7854c0 139779617871040 rcx 0x559e069d4900 94137204164864 rdx 0x40 64 rsi 0x1 1 rdi 0x7f20e5175ad0 139779259194064 rbp 0x7f20fbd26ab0 0x7f20fbd26ab0 rsp 0x7f20fbd26aa0 0x7f20fbd26aa0 r8 0x7f20e5170580 139779259172224 r9 0x7f20e43c3528 139779244832040 r10 0x7f20e4301718 139779244037912 r11 0x0 0 r12 0x7f20fa7d3000 139779618189312 r13 0x7f20eb062730 139779358730032 r14 0x7f20fa7c48e0 139779618130144 r15 0x7f20e5180100 139779259236608 rip 0x7f20ee1bc60f 0x7f20ee1bc60f <mozilla::ipc::MessageChannel::OnChannelErrorFromLink()+719> eflags 0x10202 [ IF RF ] cs 0x33 51 ss 0x2b 43 ds 0x0 0 es 0x0 0 fs 0x0 0 gs 0x0 0 SegvAnalysis: Segfault happened at: 0x7f20ee1bc60f <_ZN7mozilla3ipc14MessageChannel22OnChannelErrorFromLinkEv+719>: movl $0xa66,0x0 PC (0x7f20ee1bc60f) ok source "$0xa66" ok destination "0x0" (0x00000000) not located in a known VMA region (needed writable region)! Stack memory exhausted (SP below stack segment) SegvReason: writing NULL VMA Stacktrace: #0 0x00007f20ee1bc60f in mozilla::ipc::MessageChannel::OnChannelErrorFromLink() () at /opt/firefox/libxul.so #1 0x00007f20eb0822b0 in mozilla::ipc::ProcessLink::OnChannelError() () at /opt/firefox/libxul.so #2 0x00007f20eb06e5db in event_persist_closure () at /opt/firefox/libxul.so #3 0x00007f20eb06e1a4 in event_process_active_single_queue () at /opt/firefox/libxul.so #4 0x00007f20eb06ceef in event_process_active () at /opt/firefox/libxul.so #5 0x00007f20eb06c86f in event_base_loop () at /opt/firefox/libxul.so #6 0x00007f20eb062865 in base::MessagePumpLibevent::Run(base::MessagePump::Delegate*) () at /opt/firefox/libxul.so #7 0x00007f20ee1ac855 in MessageLoop::Run() () at /opt/firefox/libxul.so #8 0x00007f20eb066444 in base::Thread::ThreadMain() () at /opt/firefox/libxul.so #9 0x00007f20eb064cca in ThreadFunc(void*) () at /opt/firefox/libxul.so #10 0x00007f20fba8f6db in start_thread (arg=0x7f20fbd27700) at pthread_create.c:463 pd = 0x7f20fbd27700 now = <optimized out> unwind_buf = {cancel_jmp_buf = {{jmp_buf = {139779640555264, -3184634665266467588, 139779640553408, 0, 139779617481336, 140726223944936, 3282015828339698940, 3282016872767270140}, mask_was_saved = 0}}, priv = {pad = {0x0, 0x0, 0x0, 0x0}, data = {prev = 0x0, cleanup = 0x0, canceltype = 0}}} not_first_call = <optimized out> #11 0x00007f20faa6d88f in clone () at ../sysdeps/unix/sysv/linux/x86_64/clone.S:95 StacktraceAddressSignature: /opt/firefox/firefox-bin:11:/opt/firefox/libxul.so+356460f:/opt/firefox/libxul.so+42a2b0:/opt/firefox/libxul.so+4165db:/opt/firefox/libxul.so+4161a4:/opt/firefox/libxul.so+414eef:/opt/firefox/libxul.so+41486f:/opt/firefox/libxul.so+40a865:/opt/firefox/libxul.so+3554855:/opt/firefox/libxul.so+40e444:/opt/firefox/libxul.so+40ccca:/lib/x86_64-linux-gnu/libpthread-2.27.so+76db:/lib/x86_64-linux-gnu/libc-2.27.so+12188f StacktraceTop: mozilla::ipc::MessageChannel::OnChannelErrorFromLink() () at /opt/firefox/libxul.so mozilla::ipc::ProcessLink::OnChannelError() () at /opt/firefox/libxul.so event_persist_closure () at /opt/firefox/libxul.so event_process_active_single_queue () at /opt/firefox/libxul.so event_process_active () at /opt/firefox/libxul.so

This only seems to happen with a particular profile and happens even when running that profile only.

Opening this profile with a debug build from current mozilla-central I get the following in the console: [Parent 18468, Main Thread] WARNING: Cannot set transparency mode on non-popup windows.: file /home/birtles/src1/widget/gtk/nsWindow.cpp, line 4541 [Child 19349, Main Thread] WARNING: NS_ENSURE_TRUE(doc) failed: file /home/birtles/src1/dom/base/nsDOMWindowUtils.cpp, line 3495 Extension error: [Exception... "Component returned failure code: 0x80004005 (NS_ERROR_FAILURE) [nsIDOMWindowUtils.addSheet]" nsresult: "0x80004005 (NS_ERROR_FAILURE)" location: "JS frame :: resource://gre/modules/ExtensionCommon.jsm :: runSafeSyncWithoutClone :: line 65" data: no] undefined 65 [[Exception stack runSafeSyncWithoutClone@resource://gre/modules/ExtensionCommon.jsm:65:12 inject/cssPromise<@resource://gre/modules/ExtensionContent.jsm:454:13 promise callback*inject@resource://gre/modules/ExtensionContent.jsm:445:50 async*injectInto@resource://gre/modules/ExtensionContent.jsm:400:14 async*loadContentScript@file:///home/birtles/src1/obj-debug-opt/dist/bin/components/extension-process-script.js:310:63 Current stack runSafeSyncWithoutClone@resource://gre/modules/ExtensionCommon.jsm:67:129 inject/cssPromise<@resource://gre/modules/ExtensionContent.jsm:454:13 promise callback*inject@resource://gre/modules/ExtensionContent.jsm:445:50 async*injectInto@resource://gre/modules/ExtensionContent.jsm:400:14 async*loadContentScript@file:///home/birtles/src1/obj-debug-opt/dist/bin/components/extension-process-script.js:310:63 ]] [Child 19349, Main Thread] WARNING: NS_ENSURE_TRUE(doc) failed: file /home/birtles/src1/dom/base/nsDOMWindowUtils.cpp, line 3520 Extension error: [Exception... "Component returned failure code: 0x80004005 (NS_ERROR_FAILURE) [nsIDOMWindowUtils.removeSheetUsingURIString]" nsresult: "0x80004005 (NS_ERROR_FAILURE)" location: "JS frame :: resource://gre/modules/ExtensionCommon.jsm :: runSafeSyncWithoutClone :: line 65" data: no] undefined 65 [[Exception stack runSafeSyncWithoutClone@resource://gre/modules/ExtensionCommon.jsm:65:12 cleanup@resource://gre/modules/ExtensionContent.jsm:360:11 close@resource://gre/modules/ExtensionContent.jsm:906:7 inner-window-destroyed@resource://gre/modules/ExtensionContent.jsm:981:11 observe@resource://gre/modules/ExtensionContent.jsm:997:5 Current stack runSafeSyncWithoutClone@resource://gre/modules/ExtensionCommon.jsm:67:129 cleanup@resource://gre/modules/ExtensionContent.jsm:360:11 close@resource://gre/modules/ExtensionContent.jsm:906:7 inner-window-destroyed@resource://gre/modules/ExtensionContent.jsm:981:11 observe@resource://gre/modules/ExtensionContent.jsm:997:5 ]]

I'm not sure that previous error was related. I've been trying to bisect this but even after going back nearly 24 hours it still seems broken to me. Maybe an add-on updated and broke everything.

For what its worth, I upgraded Nightly again today, and I'm not seeing this problem anymore. I'm not on buildid 20181018123730.

Yeah, today's Nightly works for me too.