512 lines
14 KiB
V
512 lines
14 KiB
V
module sync
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import time
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import rand
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#flag windows -I @VROOT/thirdparty/stdatomic/win
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#flag linux -I @VROOT/thirdparty/stdatomic/nix
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#flag darwin -I @VROOT/thirdparty/stdatomic/nix
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#flag freebsd -I @VROOT/thirdparty/stdatomic/nix
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#flag solaris -I @VROOT/thirdparty/stdatomic/nix
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$if linux {
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$if tinyc {
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// most Linux distributions have /usr/lib/libatomic.so, but Ubuntu uses gcc version specific dir
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#flag -L/usr/lib/gcc/x86_64-linux-gnu/8 -L/usr/lib/gcc/x86_64-linux-gnu/9 -latomic
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}
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}
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#include <atomic.h>
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// the following functions are actually generic in C
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fn C.atomic_load_ptr(voidptr) voidptr
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fn C.atomic_store_ptr(voidptr, voidptr)
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fn C.atomic_compare_exchange_weak_ptr(voidptr, voidptr, voidptr) bool
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fn C.atomic_compare_exchange_strong_ptr(voidptr, voidptr, voidptr) bool
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fn C.atomic_exchange_ptr(voidptr, voidptr) voidptr
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fn C.atomic_fetch_add_ptr(voidptr, voidptr) voidptr
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fn C.atomic_fetch_sub_ptr(voidptr, voidptr) voidptr
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fn C.atomic_load_u16(voidptr) u16
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fn C.atomic_store_u16(voidptr, u16)
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fn C.atomic_compare_exchange_weak_u16(voidptr, voidptr, u16) bool
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fn C.atomic_compare_exchange_strong_u16(voidptr, voidptr, u16) bool
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fn C.atomic_exchange_u16(voidptr, u16) u16
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fn C.atomic_fetch_add_u16(voidptr, u16) u16
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fn C.atomic_fetch_sub_u16(voidptr, u16) u16
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fn C.atomic_load_u32(voidptr) u32
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fn C.atomic_store_u32(voidptr, u32)
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fn C.atomic_compare_exchange_weak_u32(voidptr, voidptr, u32) bool
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fn C.atomic_compare_exchange_strong_u32(voidptr, voidptr, u32) bool
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fn C.atomic_exchange_u32(voidptr, u32) u32
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fn C.atomic_fetch_add_u32(voidptr, u32) u32
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fn C.atomic_fetch_sub_u32(voidptr, u32) u32
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fn C.atomic_load_u64(voidptr) u64
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fn C.atomic_store_u64(voidptr, u64)
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fn C.atomic_compare_exchange_weak_u64(voidptr, voidptr, u64) bool
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fn C.atomic_compare_exchange_strong_u64(voidptr, voidptr, u64) bool
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fn C.atomic_exchange_u64(voidptr, u64) u64
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fn C.atomic_fetch_add_u64(voidptr, u64) u64
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fn C.atomic_fetch_sub_u64(voidptr, u64) u64
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const (
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// how often to try to get data without blocking before to wait for semaphore
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spinloops = 750
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spinloops_sem = 4000
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)
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enum BufferElemStat {
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unused = 0
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writing
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written
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reading
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}
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struct Subscription {
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mut:
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sem Semaphore
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prev &&Subscription
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nxt &Subscription
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}
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enum Direction {
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pop
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push
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}
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struct Channel {
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writesem Semaphore // to wake thread that wanted to write, but buffer was full
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readsem Semaphore // to wake thread that wanted to read, but buffer was empty
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writesem_im Semaphore
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readsem_im Semaphore
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ringbuf byteptr // queue for buffered channels
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statusbuf byteptr // flags to synchronize write/read in ringbuf
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objsize u32
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queue_length u32 // in #objects
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mut: // atomic
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write_adr C.atomic_uintptr_t // if != NULL the next obj can be written here without wait
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read_adr C.atomic_uintptr_t // if != NULL an obj can be read from here without wait
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adr_read C.atomic_uintptr_t // used to identify origin of writesem
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adr_written C.atomic_uintptr_t // used to identify origin of readsem
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write_free u32 // for queue state
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read_avail u32
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buf_elem_write_idx u32
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buf_elem_read_idx u32
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// for select
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write_subscriber &Subscription
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read_subscriber &Subscription
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write_sub_mtx u16
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read_sub_mtx u16
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}
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pub fn new_channel<T>(n u32) &Channel {
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st := sizeof(T)
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return &Channel{
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writesem: new_semaphore_init(if n > 0 { n + 1 } else { 1 })
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readsem: new_semaphore_init(if n > 0 { u32(0) } else { 1 })
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writesem_im: new_semaphore()
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readsem_im: new_semaphore()
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objsize: st
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queue_length: n
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write_free: n
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read_avail: 0
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ringbuf: if n > 0 { malloc(int(n * st)) } else { byteptr(0) }
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statusbuf: if n > 0 { vcalloc(int(n * 2)) } else { byteptr(0) }
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write_subscriber: 0
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read_subscriber: 0
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}
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}
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pub fn (mut ch Channel) push(src voidptr) {
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ch.try_push(src, false)
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}
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fn (mut ch Channel) try_push(src voidptr, no_block bool) bool {
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spinloops_, spinloops_sem_ := if no_block { 1, 1 } else { spinloops, spinloops_sem }
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mut have_swapped := false
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for {
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mut got_sem := false
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mut wradr := C.atomic_load_ptr(&ch.write_adr)
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for wradr != C.NULL {
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if C.atomic_compare_exchange_strong_ptr(&ch.write_adr, &wradr, voidptr(0)) {
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// there is a reader waiting for us
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unsafe { C.memcpy(wradr, src, ch.objsize) }
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mut nulladr := voidptr(0)
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for !C.atomic_compare_exchange_weak_ptr(&ch.adr_written, &nulladr, wradr) {
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nulladr = voidptr(0)
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}
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ch.readsem_im.post()
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return true
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}
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}
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if no_block && ch.queue_length == 0 {
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return false
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}
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// get token to read
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for _ in 0 .. spinloops_sem_ {
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if got_sem {
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break
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}
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got_sem = ch.writesem.try_wait()
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}
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if !got_sem {
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ch.writesem.wait()
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}
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if ch.queue_length == 0 {
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// try to advertise current object as readable
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mut read_in_progress := false
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C.atomic_store_ptr(&ch.read_adr, src)
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wradr = C.atomic_load_ptr(&ch.write_adr)
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if wradr != C.NULL {
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mut src2 := src
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if C.atomic_compare_exchange_strong_ptr(&ch.read_adr, &src2, voidptr(0)) {
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ch.writesem.post()
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continue
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} else {
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read_in_progress = true
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}
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}
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if !read_in_progress {
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mut null16 := u16(0)
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for !C.atomic_compare_exchange_weak_u16(&ch.read_sub_mtx, &null16, u16(1)) {
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null16 = u16(0)
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}
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if ch.read_subscriber != voidptr(0) {
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ch.read_subscriber.sem.post()
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}
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C.atomic_store_u16(&ch.read_sub_mtx, u16(0))
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}
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mut src2 := src
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for sp := u32(0); sp < spinloops_ || read_in_progress; sp++ {
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if C.atomic_compare_exchange_strong_ptr(&ch.adr_read, &src2, voidptr(0)) {
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have_swapped = true
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read_in_progress = true
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break
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}
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src2 = src
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}
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mut got_im_sem := false
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for sp := u32(0); sp < spinloops_sem_ || read_in_progress; sp++ {
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got_im_sem = ch.writesem_im.try_wait()
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if got_im_sem {
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break
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}
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}
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for {
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if got_im_sem {
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got_im_sem = false
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} else {
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ch.writesem_im.wait()
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}
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if have_swapped || C.atomic_compare_exchange_strong_ptr(&ch.adr_read, &src2, voidptr(0)) {
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ch.writesem.post()
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break
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} else {
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// this semaphore was not for us - repost in
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ch.writesem_im.post()
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src2 = src
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}
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}
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return true
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} else {
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// buffered channel
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mut space_in_queue := false
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mut wr_free := C.atomic_load_u32(&ch.write_free)
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for wr_free > 0 {
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space_in_queue = C.atomic_compare_exchange_weak_u32(&ch.write_free, &wr_free, wr_free-1)
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if space_in_queue {
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break
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}
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}
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if space_in_queue {
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mut wr_idx := C.atomic_load_u32(&ch.buf_elem_write_idx)
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for {
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mut new_wr_idx := wr_idx + 1
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for new_wr_idx >= ch.queue_length {
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new_wr_idx -= ch.queue_length
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}
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if C.atomic_compare_exchange_strong_u32(&ch.buf_elem_write_idx, &wr_idx, new_wr_idx) {
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break
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}
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}
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mut wr_ptr := ch.ringbuf
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mut status_adr := ch.statusbuf
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unsafe {
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wr_ptr += wr_idx * ch.objsize
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status_adr += wr_idx * sizeof(u16)
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}
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mut expected_status := u16(BufferElemStat.unused)
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for !C.atomic_compare_exchange_weak_u16(status_adr, &expected_status, u16(BufferElemStat.writing)) {
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expected_status = u16(BufferElemStat.unused)
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}
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unsafe {
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C.memcpy(wr_ptr, src, ch.objsize)
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}
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C.atomic_store_u16(status_adr, u16(BufferElemStat.written))
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old_read_avail := C.atomic_fetch_add_u32(&ch.read_avail, 1)
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ch.readsem.post()
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if old_read_avail == 0 {
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mut null16 := u16(0)
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for !C.atomic_compare_exchange_weak_u16(&ch.read_sub_mtx, &null16, u16(1)) {
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null16 = u16(0)
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}
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if ch.read_subscriber != voidptr(0) {
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ch.read_subscriber.sem.post()
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}
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C.atomic_store_u16(&ch.read_sub_mtx, u16(0))
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}
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return true
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} else {
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ch.writesem.post()
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}
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}
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}
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}
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pub fn (mut ch Channel) pop(dest voidptr) {
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ch.try_pop(dest, false)
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}
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fn (mut ch Channel) try_pop(dest voidptr, no_block bool) bool {
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spinloops_, spinloops_sem_ := if no_block { 1, 1 } else { spinloops, spinloops_sem }
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mut have_swapped := false
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mut write_in_progress := false
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for {
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mut got_sem := false
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if ch.queue_length == 0 {
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// unbuffered channel - first see if a `push()` has adversized
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mut rdadr := C.atomic_load_ptr(&ch.read_adr)
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for rdadr != C.NULL {
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if C.atomic_compare_exchange_strong_ptr(&ch.read_adr, &rdadr, voidptr(0)) {
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// there is a writer waiting for us
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unsafe { C.memcpy(dest, rdadr, ch.objsize) }
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mut nulladr := voidptr(0)
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for !C.atomic_compare_exchange_weak_ptr(&ch.adr_read, &nulladr, rdadr) {
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nulladr = voidptr(0)
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}
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ch.writesem_im.post()
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return true
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}
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}
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if no_block {
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return false
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}
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}
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// get token to read
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for _ in 0 .. spinloops_sem_ {
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if got_sem {
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break
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}
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got_sem = ch.readsem.try_wait()
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}
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if !got_sem {
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if no_block {
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return false
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}
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ch.readsem.wait()
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}
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if ch.queue_length > 0 {
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// try to get buffer token
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mut obj_in_queue := false
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mut rd_avail := C.atomic_load_u32(&ch.read_avail)
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for rd_avail > 0 {
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obj_in_queue = C.atomic_compare_exchange_weak_u32(&ch.read_avail, &rd_avail, rd_avail-1)
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if obj_in_queue {
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break
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}
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}
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if obj_in_queue {
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mut rd_idx := C.atomic_load_u32(&ch.buf_elem_read_idx)
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for {
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mut new_rd_idx := rd_idx + 1
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for new_rd_idx >= ch.queue_length {
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new_rd_idx -= ch.queue_length
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}
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if C.atomic_compare_exchange_weak_u32(&ch.buf_elem_read_idx, &rd_idx, new_rd_idx) {
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break
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}
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}
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mut rd_ptr := ch.ringbuf
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mut status_adr := ch.statusbuf
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unsafe {
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rd_ptr += rd_idx * ch.objsize
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status_adr += rd_idx * sizeof(u16)
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}
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mut expected_status := u16(BufferElemStat.written)
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for !C.atomic_compare_exchange_weak_u16(status_adr, &expected_status, u16(BufferElemStat.reading)) {
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expected_status = u16(BufferElemStat.written)
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}
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unsafe {
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C.memcpy(dest, rd_ptr, ch.objsize)
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}
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C.atomic_store_u16(status_adr, u16(BufferElemStat.unused))
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old_write_free := C.atomic_fetch_add_u32(&ch.write_free, 1)
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ch.writesem.post()
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if old_write_free == 0 {
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mut null16 := u16(0)
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for !C.atomic_compare_exchange_weak_u16(&ch.write_sub_mtx, &null16, u16(1)) {
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null16 = u16(0)
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}
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if ch.write_subscriber != voidptr(0) {
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ch.write_subscriber.sem.post()
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}
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C.atomic_store_u16(&ch.write_sub_mtx, u16(0))
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}
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return true
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}
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}
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// try to advertise `dest` as writable
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C.atomic_store_ptr(&ch.write_adr, dest)
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if ch.queue_length == 0 {
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mut rdadr := C.atomic_load_ptr(&ch.read_adr)
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if rdadr != C.NULL {
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mut dest2 := dest
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if C.atomic_compare_exchange_strong_ptr(&ch.write_adr, &dest2, voidptr(0)) {
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ch.readsem.post()
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continue
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} else {
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write_in_progress = true
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}
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}
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}
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if ch.queue_length == 0 && !write_in_progress {
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mut null16 := u16(0)
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for !C.atomic_compare_exchange_weak_u16(&ch.write_sub_mtx, &null16, u16(1)) {
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null16 = u16(0)
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}
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if ch.write_subscriber != voidptr(0) {
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ch.write_subscriber.sem.post()
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}
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C.atomic_store_u16(&ch.write_sub_mtx, u16(0))
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}
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mut dest2 := dest
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for sp := u32(0); sp < spinloops_ || write_in_progress; sp++ {
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if C.atomic_compare_exchange_strong_ptr(&ch.adr_written, &dest2, voidptr(0)) {
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have_swapped = true
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break
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}
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dest2 = dest
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}
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mut got_im_sem := false
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for sp := u32(0); sp < spinloops_sem_ || write_in_progress; sp++ {
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got_im_sem = ch.readsem_im.try_wait()
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if got_im_sem {
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break
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}
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}
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for {
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if got_im_sem {
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got_im_sem = false
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} else {
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ch.readsem_im.wait()
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}
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if have_swapped || C.atomic_compare_exchange_strong_ptr(&ch.adr_written, &dest2, voidptr(0)) {
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ch.readsem.post()
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break
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} else {
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// this semaphore was not for us - repost in
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ch.readsem_im.post()
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dest2 = dest
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}
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}
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return true
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}
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}
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// Wait `timeout` on any of `channels[i]` until one of them can push (`is_push[i] = true`) or pop (`is_push[i] = false`)
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// object referenced by `objrefs[i]`. `timeout = 0` means wait unlimited time
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pub fn channel_select(mut channels []&Channel, dir []Direction, mut objrefs []voidptr, timeout time.Duration) int {
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assert channels.len == dir.len
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assert dir.len == objrefs.len
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mut subscr := []Subscription{len: channels.len}
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sem := new_semaphore()
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for i, ch in channels {
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if dir[i] == .push {
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mut null16 := u16(0)
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for !C.atomic_compare_exchange_weak_u16(&ch.write_sub_mtx, &null16, u16(1)) {
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null16 = u16(0)
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}
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subscr[i].sem = sem
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subscr[i].prev = &ch.write_subscriber
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subscr[i].nxt = C.atomic_exchange_ptr(&ch.write_subscriber, &subscr[i])
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if voidptr(subscr[i].nxt) != voidptr(0) {
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subscr[i].nxt.prev = &subscr[i]
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}
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C.atomic_store_u16(&ch.write_sub_mtx, u16(0))
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} else {
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mut null16 := u16(0)
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for !C.atomic_compare_exchange_weak_u16(&ch.read_sub_mtx, &null16, u16(1)) {
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null16 = u16(0)
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}
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subscr[i].sem = sem
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subscr[i].prev = &ch.read_subscriber
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subscr[i].nxt = C.atomic_exchange_ptr(&ch.read_subscriber, &subscr[i])
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if voidptr(subscr[i].nxt) != voidptr(0) {
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subscr[i].nxt.prev = &subscr[i]
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}
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C.atomic_store_u16(&ch.read_sub_mtx, u16(0))
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}
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}
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stopwatch := if timeout == 0 { time.StopWatch{} } else { time.new_stopwatch({}) }
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mut event_idx := -1 // negative index means `timed out`
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for {
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rnd := rand.u32_in_range(0, u32(channels.len))
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for j, _ in channels {
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mut i := j + int(rnd)
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if i >= channels.len {
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i -= channels.len
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}
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if dir[i] == .push {
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if channels[i].try_push(objrefs[i], true) {
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event_idx = i
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goto restore
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}
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} else {
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if channels[i].try_pop(objrefs[i], true) {
|
|
event_idx = i
|
|
goto restore
|
|
}
|
|
}
|
|
}
|
|
if timeout > 0 {
|
|
remaining := timeout - stopwatch.elapsed()
|
|
if !sem.timed_wait(remaining) {
|
|
goto restore
|
|
}
|
|
} else {
|
|
sem.wait()
|
|
}
|
|
}
|
|
restore:
|
|
// reset subscribers
|
|
for i, ch in channels {
|
|
if dir[i] == .push {
|
|
mut null16 := u16(0)
|
|
for !C.atomic_compare_exchange_weak_u16(&ch.write_sub_mtx, &null16, u16(1)) {
|
|
null16 = u16(0)
|
|
}
|
|
subscr[i].prev = subscr[i].nxt
|
|
if subscr[i].nxt != 0 {
|
|
// just in case we have missed a semaphore during restore
|
|
subscr[i].nxt.sem.post()
|
|
}
|
|
C.atomic_store_u16(&ch.write_sub_mtx, u16(0))
|
|
} else {
|
|
mut null16 := u16(0)
|
|
for !C.atomic_compare_exchange_weak_u16(&ch.read_sub_mtx, &null16, u16(1)) {
|
|
null16 = u16(0)
|
|
}
|
|
subscr[i].prev = subscr[i].nxt
|
|
if subscr[i].nxt != 0 {
|
|
subscr[i].nxt.sem.post()
|
|
}
|
|
C.atomic_store_u16(&ch.read_sub_mtx, u16(0))
|
|
}
|
|
}
|
|
sem.destroy()
|
|
return event_idx
|
|
}
|