2071951 - Thunderbird hangs on startup when restoring session.json.

Status: RESOLVED DUPLICATE of bug 2071123

(Thunderbird :: Untriaged, defect)

Description

[Ignazio]

User Agent: Mozilla/5.0 (Windows NT 10.0; Win64; x64; rv:140.0) Gecko/20100101 Firefox/140.0

Steps to reproduce:

Started Thunderbird with a previously saved session containing multiple open tabs. During session restoration, Thunderbird became permanently unresponsive.

Actual results:

Thunderbird remained permanently unresponsive during startup while restoring the previous session. Renaming session.json to session.json.old immediately resolved the problem. Thunderbird then created a new session and started normally again. No mail accounts, messages or other profile data were affected.

Expected results:

Thunderbird should detect a failed or stalled session restore and handle it as a recoverable error instead of remaining unresponsive.

If session restoration fails, Thunderbird should preserve the existing session.json for diagnostic purposes, log the technical cause, create a clean session and continue startup.

The user should be informed that the previous session could not be restored due to a technical error, that Thunderbird has started with a new session, and that accounts and messages are not affected.

Comment 1

[Wayne Mery (:wsmwk)]

https://mzl.la/46EHTYg lists several possible matches. Do any match yours?

Comment 2

[Ignazio]

Bug 2071123 appears to be a very close match.

My case showed the same essential behavior: Thunderbird 153.2.0esr became permanently unresponsive while restoring a session containing multiple open tabs. The hang occurred again on every startup. Renaming session.json immediately restored normal startup with the same profile.

I did not collect a stack dump, so I cannot confirm that the underlying deadlock is identical to Bug 2071123.

Best regards,
Ignazio Lamberti

Comment 3

[Wayne Mery (:wsmwk)]

How long have you been running version 153?
Are any of those tabs to be restored PDF files or other types of attachments?

"automatic recovery suggested" would be a separate bug report.

Comment 4

[Ignazio]

Attachment: Sanitized copy of the original session.json that caused the startup hang

I cannot determine exactly how long I had been running version 153.2.0esr before the hang occurred.
However, I still have the original session.json.old that caused the reproducible startup hang. I checked it, and yes, two of the tabs to be restored were PDF attachments.
They were both IMAP attachments from the same message:

1. Elternbrief_Infoabend.pdf

• Elternpräsentation-DSDZ25-26.pdf
  Both were stored as contentTab entries with type=application/pdf.
  The session contained 10 tabs in total. The selected tab (selectedIndex: 9) was not one of the PDF tabs, but a normal mailMessageTab for an IMAP message.
  I have also attached a sanitized copy of the original session.json.old. Personal account/server information and message identifiers have been anonymized, while the original tab structure and the two PDF attachment tabs have been preserved.
  Best regards,
  Ignazio Lamberti

Comment 6

[Ignazio]

Dear Thunderbird Development Team,

Thank you for investigating and fixing Bug 2071123.

I would like to clarify an important detail regarding our original report, Bug 2071951, which was marked as a duplicate of Bug 2071123.

In our case, Thunderbird consistently froze during startup when attempting to restore the previous session associated with the "session.json" file.

For reasons we could not determine, Thunderbird appeared unable to process this file correctly. Removing the problematic session file allowed Thunderbird to start normally again.

Our observation therefore points specifically to a problem during session-file processing. We have not established whether the file itself was corrupted or whether its contents triggered an internal Thunderbird error.

Could you please clarify whether the fix for Bug 2071123 also addresses situations in which Thunderbird encounters an unreadable, malformed, or otherwise problematic "session.json" file during startup?

Ideally, Thunderbird should handle such a situation gracefully, recover where possible, or start a new session rather than becoming permanently unresponsive.

We would appreciate confirmation that this scenario is covered by the fix, or whether it should be investigated separately.

Thank you for your work and support.

Kind regards,
Ignazio Lamberti

Comment 7

[Max Emig [:maxe]]

Hi Ignazio,

Thunderbird could not handle restoring a session if it included at least one PDF viewer IMAP tab as well as multiple other IMAP tabs.

No, this patch does not include a generalised solution against some kind of future restored session causing yet another hang, but fixes exactly what you were reporting.

Thanks

Max