[Boost-users] [shared_ptr] Is reference counting thread safe in boost 1.38

Subject: [Boost-users] [shared_ptr] Is reference counting thread safe in boost 1.38
From: dhruva (dhruva_at_[hidden])
Date: 2009-02-21 01:26:19

Hello,
 I am trying to replace a home grown shared pointer which uses expensive lock (mutex) to make the increment and decrement thread safe. I went through the boost code and see it uses atomic operations. I am not able to figure out if the following case is handled:

1. Thread 1 has a shared_ptr and hence the reference is 1
2. Thread 1 is in the process of decrementing the reference and thread 2 is in the process of incrementing the the reference
3. If thread 1 succeeds in decrementing, the reference will become 0 and hence 'destroy' will get called.
4. Can thread 2 increment after when thread 1 is in a call to destroy?

The reference count variable is itself protected but is the call to destroy and reference count variable synchronized?

-dhruva



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