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Timers: binary heap in a fixed array - #28
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pt_sleep() inserted into a deadline-sorted list with interrupts masked. A new sleep usually has the latest deadline, so a typical insert walked every sleeper, and pt_timer_cancel() did the same. Keep the sleepers in a binary min-heap instead, an array of PT_NTIMERS (default 16) pointers inside pt_timers_t. Each env stores its slot, in place of next, so the env doesn't grow and cancel is O(log N) too. A fixed array fits PT_NO_MALLOC. A sleeper that finds every slot in use waits on the timer set for one. It sets full_wait in the same critical section as its enqueue, and pt_timer_run() broadcasts when it sees full_wait and a free slot. A slot freed by pt_timer_cancel() is handed on at the next pt_timer_run(), since cancel has no protothread_t to broadcast with. Equal deadlines no longer wake in FIFO order. Nothing documented or tested that. test_timer_heap fills the heap with random deadlines, cancels random entries, and checks the heap after every step, over 100 seeds. test_timer_full covers waiting for a slot, including after a cancel. Both catch a broken slot hand-off and a missing sift-up. Co-Authored-By: Claude Opus 5.5 <noreply@anthropic.com> Claude-Session: https://claude.ai/code/session_01SR7v9BVsFrHiEhQBSqZmAs
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pt_sleep()inserted into a deadline-sorted list with interrupts masked. A new sleep usually has the latest deadline, so a typical insert walked every sleeper, andpt_timer_cancel()did the same.This keeps the sleepers in a binary min-heap instead, an array of
PT_NTIMERS(default 16) pointers insidept_timers_t. A sleep, a cancel, and each wakeup are now O(log N) with interrupts masked. Each env stores its slot in place ofnext, so it doesn't grow. There's no API change.pt_sleep()waits for one, and its sleep starts then.pt_timer_run()hands on a freed slot, including one freed bypt_timer_cancel()(at the next run, since cancel has noprotothread_t).New tests:
test_timer_heapchecks the heap after every step, with random deadlines and cancels, over 100 seeds.test_timer_fullcovers waiting for a slot.Both fail against a broken slot hand-off and a missing sift-up. Passes locally with gcc and clang-22, several
PT_NWAIT/PT_NTIMERSsettings, ASan/UBSan, C++11, and freestanding C99.🤖 Generated with Claude Code
https://claude.ai/code/session_01SR7v9BVsFrHiEhQBSqZmAs