1964406 - Multiple running flatpak instances (profiles) cause content process to crash

Status: RESOLVED FIXED

(Toolkit :: Crash Reporting, defect)

Description

[Kestrel]

STR:

1. Install latest flatpak Nightly (unofficial) on Ubuntu 25.04:
   flatpak install https://gitlab.com/projects261/firefox-nightly-flatpak/-/raw/main/firefox-nightly.flatpakref
2. Launch two instances with separate profiles:
   flatpak run org.mozilla.FirefoxNightly -P

Alternatively with latest flatpak Beta:

flatpak remote-add --if-not-exists flathub-beta https://flathub.org/beta-repo/flathub-beta.flatpakrepo
flatpak install org.mozilla.firefox/x86_64/beta
flatpak run org.mozilla.firefox/x86_64/beta -P

Only first instance works, content processes always crash in second instance.

Terminal error:
[Parent 2, IPC I/O Parent] WARNING: process 48 exited on signal 11: file /builds/worker/checkouts/gecko/ipc/chromium/src/chrome/common/process_watcher_posix_sigchld.cc:132

Regression window between 2025-04-18 and 2025-04-19.

Likely regressed by Bug 1620998.

Comment 1

[BugBot [:suhaib / :marco/ :calixte]]

:gsvelto, since you are the author of the regressor, bug 1620998, could you take a look? Also, could you set the severity field?

For more information, please visit BugBot documentation.

Comment 2

[Gabriele Svelto [:gsvelto]]

Could you please get a stack trace of a crashing content process? I don't understand why this would work differently on Flatpak so I need a hint of what's going wrong.

Comment 3

[BugBot [:suhaib / :marco/ :calixte]]

The bug is marked as tracked for firefox139 (beta) and tracked for firefox140 (nightly). However, the bug still isn't assigned.

:gcp, could you please find an assignee for this tracked bug? Given that it is a regression and we know the cause, we could also simply backout the regressor. If you disagree with the tracking decision, please talk with the release managers.

For more information, please visit BugBot documentation.

Comment 4

[Kestrel]

It works after restarting from inside the browser (type "restart" in the address bar and click "Restart Nightly").

It works when running from inside the flatpak shell so gdb cannot be used to stack trace and there is nothing listed in about:crashes.

flatpak run --command=sh org.mozilla.FirefoxNightly
/app/bin/firefox-nightly

Comment 5

[Donal Meehan [:dmeehan]]

This is the final week of beta for Fx139, with only 2 beta builds left
:gsvelto, any concerns with a fix for this week?

Comment 6

[Gabriele Svelto [:gsvelto]]

I still don't know what the problem is but I have a hunch. I'll write a tentative patch and we'll see if it fixes the issue. In the meantime I'll try to repo locally but analyzing Flatpak issues always takes a while.

Comment 7

[Gabriele Svelto [:gsvelto]]

Attachment: Bug 1964406 - Prevent child processes from crashing if the crash helper wasn't launched r=afranchuk

Comment 8

[Gabriele Svelto [:gsvelto]]

Setting the leave-open flag since I'm not sure if this patch will fix the issue. We'll have to verify that before we close the bug.

Comment 9

[Pulsebot]

Pushed by [e-mail]:
https://hg.mozilla.org/integration/autoland/rev/5fc9bc094fd0
Prevent child processes from crashing if the crash helper wasn't launched r=afranchuk

Comment 10

[Sandor Molnar[:smolnar]]

https://hg.mozilla.org/mozilla-central/rev/5fc9bc094fd0

Comment 11

[Kestrel]

Fixed for me with the latest flatpak Nightly 140.0a1 (2025-05-14).

Comment 12

[Gabriele Svelto [:gsvelto]]

Thank you for confirming the fix. I'll file a follow-up to investigate why the crash helper isn't starting properly when using multiple instances.

Comment 13

[BugBot [:suhaib / :marco/ :calixte]]

The patch landed in nightly and beta is affected.
:gsvelto, is this bug important enough to require an uplift?

• If yes, please nominate the patch for beta approval.
  • See https://wiki.mozilla.org/Release_Management/Requesting_an_Uplift for documentation on how to request an uplift.
• If no, please set status-firefox139 to wontfix.

For more information, please visit BugBot documentation.

Comment 14

[Gabriele Svelto [:gsvelto]]

Attachment: Bug 1964406 - Prevent child processes from crashing if the crash helper wasn't launched r=afranchuk

Original Revision: https://phabricator.services.mozilla.com/D249037

Comment 15

[Phabricator Automation]

firefox-beta Uplift Approval Request

• User impact if declined: Multiple sessions of Firefox launched using the same version crash
• Code covered by automated testing: no
• Fix verified in Nightly: yes
• Needs manual QE test: no
• Steps to reproduce for manual QE testing: no
• Risk associated with taking this patch: low
• Explanation of risk level: This is a straightforward change that ensures we don't crash in a corner-case
• String changes made/needed: none
• Is Android affected?: no

Comment 16

[Pulsebot]

https://hg.mozilla.org/releases/mozilla-beta/rev/5f48cfb9b477