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use std
use sys
use "atomic.use"
use "common.use"
use "mutex.use"
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)
}
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