[#1010996] Not correct double checked locking in CreateAndLoadInitialTypesMapping

Date:
2011-02-22 10:36 Priority:
3

State:
Open

Submitted by:
Alex A Ermoshenko (erax) Assigned to:
Nobody (None)

Npgsql Version:
2.0.11 Category:

Group: Resolution:
None

Summary:
Not correct double checked locking in CreateAndLoadInitialTypesMapping

Detailed description
Our server could not start normally, when hаs big queue of requests from users. We are healed this by making pre-heating (warming up) the server - creating multiple connections to the database before processing requests. I read you comments on this method, you wrote about "... problem with temporarily having two copies of the same mapping", in our situation created 14 NpgsqlBackendTypeMapping objects :-) You variant of code: CreateAndLoadInitialTypesMapping { if(mapping = TryGetLoadedMapping()) return mapping; newMapping = CreateAndLoadMapping(); if(mapping = TryGetLoadedMapping()) return mapping; lock(mappings) { if(mapping = TryGetLoadedMapping()) return mapping; mappings.Add(newMapping); } } Proposed variant: CreateAndLoadInitialTypesMapping { if(mapping = TryGetLoadedMapping()) return mapping; lock(mappings) { if(mapping = TryGetLoadedMapping()) return mapping; newMapping = CreateAndLoadMapping(); mappings.Add(newMapping); } }

Followup

Message
Date: 2011-02-22 10:55 Sender: Alex A Ermoshenko i forgot returns mappings.Add(newMapping); return newMapping;

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