fix: Fix dde-session not start after treeland logged in

[calsys456]

This will work as intended, at least for now...

Summary by Sourcery

Bug Fixes:

• Prevent dde-session from failing to start after Treeland login by deferring VT signal handler setup until after the user process is spawned.

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[sourcery-ai]

Reviewer's guide (collapsed on small PRs)

Reviewer's Guide

Adjusts Treeland VT signal handler setup to temporarily disable it during session process startup to avoid a VT RELDISP-induced malloc deadlock, and encapsulates the handler registration in TreelandConnector so it can be reapplied after login.

Sequence diagram for VT signal handler handling during session startup

sequenceDiagram
    participant Display
    participant Auth
    participant VirtualTerminal
    participant DaemonApp
    participant TreelandConnector

    Display->>Auth: connect(userProcessFinished)
    Display->>VirtualTerminal: setVtSignalHandler(nullptr, nullptr)
    Display->>Auth: startUserProcess(sessionExec, cookie)
    Auth-->>Display: userProcessStarted
    Display->>DaemonApp: treelandConnector()
    DaemonApp-->>Display: TreelandConnector
    Display->>TreelandConnector: setSignalHandler()
    TreelandConnector->>VirtualTerminal: setVtSignalHandler(onAcquireDisplay, onReleaseDisplay)
    Auth-->>Display: userProcessFinished(exitCode)

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Updated class diagram for TreelandConnector VT signal handler management

classDiagram
    class Display {
        +userProcessFinished()
    }

    class Auth {
        +startUserProcess(execPath, cookie)
    }

    class VirtualTerminal {
        +setVtSignalHandler(onAcquireCallback, onReleaseCallback)
    }

    class TreelandConnector {
        +TreelandConnector()
        +~TreelandConnector()
        +isConnected() bool
        +setPrivateObject(ddm)
        +setSignalHandler()
        +connect(socketPath)
        +switchToGreeter()
    }

    class DaemonApp {
        +treelandConnector() TreelandConnector*
    }

    Display --> Auth : uses
    Display --> DaemonApp : uses
    DaemonApp --> TreelandConnector : provides
    TreelandConnector --> VirtualTerminal : configures VT signals
    Display --> VirtualTerminal : temporarily disables VT signals

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File-Level Changes

Change	Details	Files
Temporarily disable VT signal handling during user session process startup and re-enable it afterward via TreelandConnector.	Before starting the user desktop process, clear the VirtualTerminal VT signal handler to avoid a RELDISP-triggered glibc malloc arena deadlock during fork() After starting the user desktop process, re-register the VT signal handler by calling the TreelandConnector helper method	src/daemon/Display.cpp
Encapsulate Treeland VT signal handler registration into a dedicated TreelandConnector method so it can be reused.	Move the initial VirtualTerminal::setVtSignalHandler(onAcquireDisplay, onReleaseDisplay) call from the TreelandConnector constructor into a new setSignalHandler() method Expose setSignalHandler() in the TreelandConnector header for external callers Use setSignalHandler() in the TreelandConnector constructor to keep existing initialization behavior	src/daemon/TreelandConnector.cpp src/daemon/TreelandConnector.h

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[sourcery-ai]

Hey - I've left some high level feedback:

• The FIXME comment about VT RELDISP and glibc malloc deadlock is the only explanation for the change; consider briefly documenting why moving setVtSignalHandler after startUserProcess avoids the deadlock and what assumptions this relies on, so future refactors don’t inadvertently regress it.
• Now that TreelandConnector’s constructor no longer unconditionally sets the VT signal handler, make it explicit in the class contract (e.g., via naming or comments) that setSignalHandler() must be called after construction, and consider guarding against multiple calls or ensuring it’s safe to call idempotently.
• Review whether the destructor should explicitly reset or clear the VT signal handler now that it is set later via setSignalHandler() rather than in the constructor, to avoid leaving global state in an unexpected configuration on teardown.

Prompt for AI Agents

Please address the comments from this code review:

## Overall Comments
- The FIXME comment about VT RELDISP and glibc malloc deadlock is the only explanation for the change; consider briefly documenting why moving `setVtSignalHandler` after `startUserProcess` avoids the deadlock and what assumptions this relies on, so future refactors don’t inadvertently regress it.
- Now that `TreelandConnector`’s constructor no longer unconditionally sets the VT signal handler, make it explicit in the class contract (e.g., via naming or comments) that `setSignalHandler()` must be called after construction, and consider guarding against multiple calls or ensuring it’s safe to call idempotently.
- Review whether the destructor should explicitly reset or clear the VT signal handler now that it is set later via `setSignalHandler()` rather than in the constructor, to avoid leaving global state in an unexpected configuration on teardown.

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[deepin-ci-robot]

[APPROVALNOTIFIER] This PR is NOT APPROVED

This pull-request has been approved by: calsys456, zccrs

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