Mutex for Kotlin Common #494
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bbrockbernd
commented
Dec 10, 2024
bbrockbernd
commented
- Fair mutex for Kotlin/Common
- Thread parking based on futex/ulock/WaitOnAddress
- Thread parking based on pthread_cond and pthread_mutex
… and prevent value capturing in block() by defining contract. Fix expected constructor
| pthread_mutex_destroy(&pc->mutex); | ||
| pthread_cond_destroy(&pc->cond); | ||
| free(pc); | ||
| } |
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cinterop, while useful, should be avoided in Kotlin libraries, because libraries containing cinterop declarations get compiled to artifacts containing LLVM bitcode, whose representation can change across versions of the Kotlin compiler in incompatible ways: https://github.com/Kotlin/kotlinx-atomicfu/pull/440/files
Fortunately, it seems like everything here can be rewritten in pure Kotlin/Native, without cinterop.
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Alright that is good to know!
The reason why I used cinterop is because the provided posix library in kotlin/native is slightly different over different platforms.
For instance, on windows you use pthread_cond_tVar and on linux pthread_cond_t. Also the pthread_cond_init function is not available in at the nativeMain sourceset.
So instead of having to duplicate this over the platforms, I thought this would be the cleanest solution.
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Yep, the function API differences are why https://github.com/Kotlin/kotlinx-atomicfu/pull/440/files had to duplicate code and couldn't write it in nativeMain. That's a pity, but what can you do.
| actual fun isLocked(): Boolean = locked | ||
| actual fun tryLock(): Boolean = true | ||
| actual fun lock(): Unit { locked = true } | ||
| actual fun unlock(): Unit { locked = false } |
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Since the mutex is reentrant, you need to maintain a counter instead so the deepest unlock call does not release the mutex.
