RDKEMW-21466: crash Observed in Vipa while zapping Linear channels

[dp0000]

Adds a lifecycle guard to DrmSession — three new methods (AcquireForUse(), ReleaseAfterUse(), PrepareForDestruction()) using a mutex + condition variable to track in-flight decrypt operations and block deletion until they finish.

Guards every decrypt() call in the GStreamer decryptor plugin (gstcdmidecryptor.cpp) with AcquireForUse() / ReleaseAfterUse(), so the session can't be freed mid-operation.

Calls PrepareForDestruction() before every delete in DrmSessionManager (session clearing, slot reuse/eviction), ensuring any in-flight decrypt drains first .

Minor fix: a sinkCaps reference-counting tweak to avoid accessing freed caps after unlocking the mutex.

[Copilot]

Pull request overview

This PR aims to prevent a use-after-free crash during rapid linear channel zaps by introducing a lifecycle guard on DrmSession and applying it around GStreamer decrypt operations, while also ensuring session teardown attempts to wait for in-flight decrypt work to finish.

Changes:

• Added DrmSession lifecycle-guard APIs (AcquireForUse(), ReleaseAfterUse(), PrepareForDestruction()) backed by a mutex/condition variable.
• Wrapped GStreamer decrypt calls with acquire/release guard calls to avoid decrypt running concurrently with session teardown.
• Updated DrmSessionManager deletion paths to call PrepareForDestruction() before deleting sessions; adjusted sink caps handling to avoid using freed caps after unlocking.

Reviewed changes

Copilot reviewed 4 out of 4 changed files in this pull request and generated 5 comments.

File	Description
gst-plugins/drm/gst/gstcdmidecryptor.cpp	Guards decrypt calls with AcquireForUse()/ReleaseAfterUse() and adjusts sink caps refcounting around unlock.
drm/DrmSessionManager.cpp	Calls PrepareForDestruction() before deleting DrmSession instances in multiple teardown/eviction paths.
drm/DrmSession.h	Adds lifecycle guard members and declares new lifecycle guard methods.
drm/DrmSession.cpp	Implements lifecycle guard methods using mutex/condition_variable and bounded wait.

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