Integration #45
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Integration #45
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Sync with upstream before checking in new workloads
CLH is a starvation-free queue spinlock which has FCFS (first come, first served) order like MCS spinlock. CLH spinlock is simpler than MCS spinlock, and each thread is spinning on its previous node's wait flag. Our CLH spinlock has an optional parameter to disable SEVL and WFE.
clh_unlock() now returns node->prev directly. Also disable wfe() for all non-aarch64 systems by default.
Now sweep mode has 5 tests: -c 0ns -p 0ns (heavy load) -c 200ns -p 0ns (baseline) -c 1000ns -p 0ns (baseline) -c 200ns -p 1000ns (median load) -c 1000ns -p 5000ns (light load)
Because each thread may finish and join randomly, some thread may reference other thread's __thread (thread local storage) even if that thread has been joined (removed). This will cause segmentation fault. Another issue is DDEBUG mode printf may cause clh_spinlock live lock if thread number is too high.
This may reflect the real unlock state
Need to save node->prev to a temporary variable, because once clh_unlock() has been called, the current clh_node may be used by another thread for many times and node->prev value might be changed. Therefore two thread may end up using the same clh_node next time and cause circular linked list problem (live-lock on the same clh_node)
Lockhammer clh (Craig Landin Hagersten, 1994) queue spinlocks from Arm
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New CLH spinlock workload