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Firefox process stays behind after quit (Windows 10)

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When I quit Firefox, the process stays running forever; I have to open the task manager and kill it. (I wait until CPU usage is down to 0 so I know it's actually done, so it doesn't think it crashed.) Running Windows 10. I think this started more or less when the Anniversary Update landed.

To prevent wasted time from either party, here are some things I already tried:

  • disabled all extensions one by one
  • fresh profile
  • fresh install of Developer Edition
  • wiped all traces of Firefox from my system, and still got this on a fresh install → 32 and 64 bit, latest release, oldest release I was able to download, Developer Edition
  • switched antivirus
  • turned antivirus off entirely
  • Windows' own safe mode
When I quit Firefox, the process stays running forever; I have to open the task manager and kill it. (I wait until CPU usage is down to 0 so I know it's actually done, so it doesn't think it crashed.) Running Windows 10. I think this started more or less when the Anniversary Update landed. To prevent wasted time from either party, here are some things I already tried: * disabled all extensions one by one * fresh profile * fresh install of Developer Edition * wiped all traces of Firefox from my system, and still got this on a fresh install → 32 and 64 bit, latest release, oldest release I was able to download, Developer Edition * switched antivirus * turned antivirus off entirely * Windows' own safe mode

Modified by lalomartins

Additional System Details

Installed Plug-ins

  • Shockwave Flash 23.0 r0

Application

  • User Agent: Mozilla/5.0 (Windows NT 10.0; Win64; x64; rv:49.0) Gecko/20100101 Firefox/49.0

More Information

FredMcD
  • Top 10 Contributor
4245 solutions 59390 answers
How to crash Firefox; Instructions here; https://developer.mozilla.org/en-US/docs/Mozilla/How_to_report_a_hung_Firefox --------------- You did not say if you tried Firefox in Safe Mode. ----------- '''https://support.mozilla.org/en-US/kb/firefox-hangs-or-not-responding''' '''https://support.mozilla.org/kb/Firefox+is+already+running+but+is+not+responding'''

Question owner

Hi FredMcD, thanks for your reply. Here's the results along with some extra debugging:

  • crashfirefox.exe fails on my stable install (whether I run it while the process is hanging, or when it's running normally) with “Could not create remote thread.” I guess it's not 64b-compatible? With Developer Edition it hangs.
  • I couldn't find any other way to generate a crash report. I thought I could trick Developer Edition into doing it but no. Which makes sense since, well, it's not crashing. A report would only be meaningful if I could make it crash after it's in the hanging state, and that seems epistemologically difficult ;-)
  • Issue also happens in Safe Mode. (BTW it wasn't trivial at all to get to Safe Mode to start with, since the browser isn't able to restart.)
  • Playing around with a clean profile, I discovered one and only one situation where it exits successfully: if I change settings to “When Firefox starts: Show a blank page”, and then quit without navigating to anything at all, it quits. If I open anything at all, even the settings UI, the process hangs.
  • Memory usage displayed in the task manager after CPU reaches 0 varies according to how many tabs I had open and, I think, their content.
  • It makes no difference whether I close the window (using the X button or alt-f4) or exit Firefox via the menu.
  • And BTW it's not a matter of waiting it out. Sometimes I forget to kill it and it stays there hanging for hours while I'm doing Chrome work.
  • The Developer Edition install has multiprocess (Electrolysis) on, the stable install doesn't. That doesn't seem to make a difference. However, only one process stays behind. (That said, even when it's running, with 4 tabs open, I only see 2 processes — so maybe I misunderstand how Electrolysis works, or how to list/count processes on Windows.)

FredMcD said

How to crash Firefox; Instructions here; https://developer.mozilla.org/en-US/docs/Mozilla/How_to_report_a_hung_Firefox

You did not say if you tried Firefox in Safe Mode.


https://support.mozilla.org/en-US/kb/firefox-hangs-or-not-responding

https://support.mozilla.org/kb/Firefox+is+already+running+but+is+not+responding

Hi FredMcD, thanks for your reply. Here's the results along with some extra debugging: * crashfirefox.exe fails on my stable install (whether I run it while the process is hanging, or when it's running normally) with “Could not create remote thread.” I guess it's not 64b-compatible? With Developer Edition it hangs. * I couldn't find any other way to generate a crash report. I thought I could trick Developer Edition into doing it but no. Which makes sense since, well, it's not crashing. A report would only be meaningful if I could make it crash after it's in the hanging state, and that seems epistemologically difficult ;-) * Issue also happens in Safe Mode. (BTW it wasn't trivial at all to get to Safe Mode to start with, since the browser isn't able to restart.) * Playing around with a clean profile, I discovered one and only one situation where it exits successfully: if I change settings to “When Firefox starts: Show a blank page”, and then quit without navigating to anything at all, it quits. If I open anything at all, even the settings UI, the process hangs. * Memory usage displayed in the task manager after CPU reaches 0 varies according to how many tabs I had open and, I think, their content. * It makes no difference whether I close the window (using the X button or alt-f4) or exit Firefox via the menu. * And BTW it's not a matter of waiting it out. Sometimes I forget to kill it and it stays there hanging for hours while I'm doing Chrome work. * The Developer Edition install has multiprocess (Electrolysis) on, the stable install doesn't. That doesn't seem to make a difference. However, only one process stays behind. (That said, even when it's running, with 4 tabs open, I only see 2 processes — so maybe I misunderstand how Electrolysis works, or how to list/count processes on Windows.) ''FredMcD [[#answer-935158|said]]'' <blockquote> How to crash Firefox; Instructions here; https://developer.mozilla.org/en-US/docs/Mozilla/How_to_report_a_hung_Firefox --------------- You did not say if you tried Firefox in Safe Mode. ----------- '''https://support.mozilla.org/en-US/kb/firefox-hangs-or-not-responding''' '''https://support.mozilla.org/kb/Firefox+is+already+running+but+is+not+responding''' </blockquote>
FredMcD
  • Top 10 Contributor
4245 solutions 59390 answers

Create a batch file on your Windows computer and call it something like ‘KillFirefox.bat’ Place this in the batch file;

TASKKILL /IM Firefox.exe /t

Now place a shortcut on the desktop to the batch.

Create a batch file on your Windows computer and call it something like ‘KillFirefox.bat’ Place this in the batch file; TASKKILL /IM Firefox.exe /t Now place a shortcut on the desktop to the batch.