PowerMax driver may deadlock moving volumes between SGs

Bug #1980870 reported by Gorka Eguileor
This bug affects 1 person
Affects Status Importance Assigned to Milestone
In Progress
Gorka Eguileor

Bug Description

There's a potential deadlock scenario in PowerMax's masking.py move_volume_between_storage_groups" method.

The method uses 2 locks, one for the source Storage Group and another for the destination Storage Group, and it could happen that if 2 requests going in opposite directions are received simultaneously their first lock acquisition interleaves resulting in a deadlock situation.

    def move_volume_between_storage_groups(
            self, serial_number, device_id, source_storagegroup_name,
            target_storagegroup_name, extra_specs, force=False,

The scenario would be like this:

- User requests an instance migration from A to B
- User requests an instance migration from B to A
- Driver acquires the first lock for A-to-B which is something like cinder-emc-sg-SGA-###
- Driver acquires the first lock for B-to-A which is something like cinder-emc-sgSGB-###

The deadlock happens because A-to-B waits forever for the lock held by the B-to-A operation, which in turn cannot proceed because it’s waiting for lock help by A-to-B.

Changed in cinder:
status: New → In Progress
Revision history for this message
Sofia Enriquez (lsofia-enriquez) wrote :
Changed in cinder:
importance: Undecided → Low
tags: added: deadlock powermax
Eric Harney (eharney)
tags: added: drivers
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