1995973 - Firefox hangs on Mac Apple M4 Pro OS Tahoe 26.0.1 #184636

Status: RESOLVED DUPLICATE of bug 1982717

(Firefox :: Untriaged, defect)

Description

[natraj]

User Agent: Mozilla/5.0 (Macintosh; Intel Mac OS X 10.15; rv:144.0) Gecko/20100101 Firefox/144.0

Steps to reproduce:

It just hangs and no specific reason or action initiated caused the hang do find the analysis of the hang below int he actual results section.

Actual results:

This is actually a hang report (not a full crash) - Firefox became unresponsive for 1.08 seconds on October 23, 2025. The issue appears to be an infinite loop or stuck recursive call in the XUL rendering engine.
Key Issues Identified:

XUL Engine Loop: The stack trace shows repeated calls to the same memory address in XUL (Firefox's rendering library), indicating the main thread was stuck
Low Disk Space: 128.73 GB free (warning threshold: 3 GB) - could impact performance
GPU Restarts: 2 GPU restarts detected - potential graphics driver issues
Dual Display Setup: Running on built-in Retina + Dell U3419W external monitor

Comment 1

[BugBot [:suhaib / :marco]]

The Bugbug bot thinks this bug should belong to the 'Core::Graphics' component, and is moving the bug to that component. Please correct in case you think the bot is wrong.

Comment 2

[natraj]

Infinite Recursion in XUL Layout Engine

Identical Memory Address Loop

11 ??? (XUL + 17409672) [0x11f1da688]
11 ??? (XUL + 17409672) [0x11f1da688]
11 ??? (XUL + 17409672) [0x11f1da688]

The exact same memory address (0x11f1da688) is being called repeatedly - this is the smoking gun. This isn't a normal call stack; it's the same function hitting the same instruction point over and over.

2. Frame Rate Collapse Pattern

   Frame 1: 577 FPS → Normal rendering
   Frame 2: 6.56 FPS → Defer time spikes to 147ms (hang begins)
   Frame 3: 3.26 FPS → Defer time: 304ms (hang worsens)
   Frame 4: 2.30 FPS → Defer time: 426ms (peak hang)

The "Defer Length" shows the rendering thread waiting 426ms - it's blocked waiting for the main thread to finish its loop.

The XUL rendering engine entered an infinite recursion loop while calculating layout or style for a specific DOM element. This happens at offset 17409672 in the XUL library, which is typically in the layout reflow or CSS recalculation code.

Issue:
A webpage with circular CSS dependencies or complex flexbox/grid layout that caused the layout engine to endlessly recalculate element positions, especially across your dual-monitor setup (Retina 3456x2234 + Dell 3440x1440).
Contributing Factors:

2 GPU restarts before the hang indicates graphics driver instability
Dual display configuration with different resolutions increases layout complexity
Low-ish disk space (128 GB) may have prevented proper swap file operations

the complete log is available here.

https://drive.google.com/file/d/1NKw55KMNVw6-SrvFJ7c1fIwI_PLV5fEi/view?usp=drive_link

Comment 3

[08xjcec48]

Please post your findings here: Bug 1982717.