StoreGate: Fix potential deadlock between SGImplSvc and DataProxy

The SGImplSvc::proxy methods take out a lock on the store, fetch the proxy, then call isValid() on the proxy. DataProxy::isValid() will acquire a lock on the proxy and than can call back to the store via TransientAddress::contextFromStore(). Thus, we can get a deadlock if SGImplSvc::proxy() is called in one thread and DataProxy::isValid() in another.

Resolve by releasing the SGImplSvc lock in proxy() before calling DataProxy::isValid().

This merge request affects 1 package:

• Control/StoreGate

Adding @ssnyder as watcher

added Core master review-pending-level-1 labels

CI Result SUCCESS (hash 3ab73357)

	Athena	AthSimulation	AnalysisBase	AthGeneration
externals
cmake
make
required tests
optional tests

Full details available on this CI monitor view
Athena: number of compilation errors 0, warnings 7
AthSimulation: number of compilation errors 0, warnings 0
AnalysisBase: number of compilation errors 0, warnings 0
AthGeneration: number of compilation errors 0, warnings 0
For experts only: Jenkins output [CI-MERGE-REQUEST-CC7 16722]

I'm new to multi-threading, so it took me a bit to figure out that the lock was removed by the scope, but this change looks good to me. Approving. (L2)

added review-approved label and removed review-pending-level-1 label

merged

mentioned in commit 2582b90e

added sweep:ignore label