[release/6.0] Fix ep_rt_atomic_compare_exchange_size_t in Mono EventPipe shim. #58369
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ep_rt_atomic_compare_exchange_size_t was always truncated to gint32 on Mono 64-bit platforms. This commit use 32 or 64-bit cas version depending on SIZEOF_SIZE_T. NOTE, CoreCLR used a template function for this and already picks 32 or 64 bit version depending on size of size_t. ep_rt_atomic_compare_exchange_size_t is currently used to reflect size of EventPipe buffer manager buffers and will most likely never need more than 2GB of data, but better to fix it and inline with CoreCLR shim implementation.
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marek-safar
approved these changes
Aug 30, 2021
ghost
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Backport of #58164 to release/6.0
/cc @lambdageek @lateralusX
Customer Impact
On Mono, in cases where the total size of reserved EventPipe buffer manager buffers exceed 2GB, there will be EventPipe data corruption on 64-bit platforms.
CoreCLR is not affected.
Testing
CI
Risk
Low. The event pipe reserved buffers should not approach that size in normal operation (each individual buffer is capped at 1mb. So we would need concurrent event pipe events on >2048 threads) . A workaround is to decrease the amount of logging, or the concurrency of the system.