ref: 0f7fbc2dcbb934a3aa62aa4a69db432b4d20b7c1
dir: /lib/thread/condvar+linux.myr/
use std use sys use "atomic" use "common" use "mutex" pkg thread = type cond = struct _mtx : mutex# _seq : int32 ;; const mkcond : (mtx : mutex# -> cond) const condwait : (cond : cond# -> void) const condsignal : (cond : cond# -> void) const condbroadcast : (cond : cond# -> void) ;; const mkcond = {mtx -> [._mtx = mtx, ._seq = 0] } const condwait = {cond var seq var mtx mtx = cond._mtx seq = cond._seq mtxunlock(mtx) sys.futex(&cond._seq, sys.Futexwait | sys.Futexpriv, seq, Zptr, Zptr, 0) /* We need to atomically set the mutex to contended. This allows us to pass responsibility for waking up the potential other waiters on to the unlocker of the mutex. */ while xchg(&mtx._state, Contended) != Unlocked sys.futex(&mtx._state, sys.Futexwait | sys.Futexpriv, \ Contended, Zptr, Zptr, 0) ;; } const condsignal = {cond : cond# xadd(&cond._seq, 1) sys.futex(&cond._seq, sys.Futexwake | sys.Futexpriv, 1, Zptr, Zptr, 0) } const condbroadcast = {cond : cond# xadd(&cond._seq, 1) /* The futex docs seem to be broken -- the timeout parameter seems to be used for the number of threads to move, and is not ignored when requeueing */ sys.futex(&cond._seq, sys.Futexcmprequeue | sys.Futexpriv, \ 1, (0x7fffffff : sys.timespec#), \ &cond._mtx._state, cond._seq) }