Is it possible to write a CHESS test that proves that reads and writes of 64-bit values are not atomic on 32-bit systems?

Question

Is it possible to write a CHESS test that proves that reads and writes of 64-bit values are not atomic on 32-bit systems?

Answer 1

At the MSIL level, I believe that a read/write of a 64-bit value is a single instruction. Since we instrument at the MSIL level, the answer would then be "no".

-- Tom

Answer 2

Yes you are right about the single instruction. I ran ildasm on "long l = 10L;" and "int i = 10;" and both compile to "ldc.i4.s 10" in MSIL.

My next question is: Is it possible to write a CHESS test that fails because a long was read using "=" instead of Interlocked.Read()?

Answer 3

The answer also is "no" because of the same reason above and the fact that CHESS serializes the execution of a multi-threaded program, which ends up having the effect of treating a read/write of a 64-bit value as atomic.  Now, with race detection turned on, CHESS will find that read/writes of longs (without any surrounding synchronization) have races, where it won't complain about interlocked operations. But same is true for 32-bit values.

-- Tom

Answer 4

Okay thanks Tom.