sync: simplify `WaitGroup` and `PoolProcessor` and use atomic counters (#8715)
parent
d03c1d615a
commit
835b3b2b81
|
@ -4,6 +4,9 @@ import sync
|
||||||
|
|
||||||
import runtime
|
import runtime
|
||||||
|
|
||||||
|
[trusted]
|
||||||
|
fn C.atomic_fetch_add_u32(voidptr, u32) u32
|
||||||
|
|
||||||
pub const (
|
pub const (
|
||||||
no_result = voidptr(0)
|
no_result = voidptr(0)
|
||||||
)
|
)
|
||||||
|
@ -14,9 +17,8 @@ mut:
|
||||||
njobs int
|
njobs int
|
||||||
items []voidptr
|
items []voidptr
|
||||||
results []voidptr
|
results []voidptr
|
||||||
ntask int // writing to this should be locked by ntask_mtx.
|
ntask u32 // reading/writing to this should be atomic
|
||||||
ntask_mtx &sync.Mutex
|
waitgroup sync.WaitGroup
|
||||||
waitgroup &sync.WaitGroup
|
|
||||||
shared_context voidptr
|
shared_context voidptr
|
||||||
thread_contexts []voidptr
|
thread_contexts []voidptr
|
||||||
}
|
}
|
||||||
|
@ -44,17 +46,16 @@ pub fn new_pool_processor(context PoolProcessorConfig) &PoolProcessor {
|
||||||
if isnil(context.callback) {
|
if isnil(context.callback) {
|
||||||
panic('You need to pass a valid callback to new_pool_processor.')
|
panic('You need to pass a valid callback to new_pool_processor.')
|
||||||
}
|
}
|
||||||
pool := &PoolProcessor {
|
mut pool := &PoolProcessor {
|
||||||
items: []
|
items: []
|
||||||
results: []
|
results: []
|
||||||
shared_context: voidptr(0)
|
shared_context: voidptr(0)
|
||||||
thread_contexts: []
|
thread_contexts: []
|
||||||
njobs: context.maxjobs
|
njobs: context.maxjobs
|
||||||
ntask: 0
|
ntask: 0
|
||||||
ntask_mtx: sync.new_mutex()
|
|
||||||
waitgroup: sync.new_waitgroup()
|
|
||||||
thread_cb: voidptr(context.callback)
|
thread_cb: voidptr(context.callback)
|
||||||
}
|
}
|
||||||
|
pool.waitgroup.init()
|
||||||
return pool
|
return pool
|
||||||
}
|
}
|
||||||
|
|
||||||
|
@ -104,16 +105,9 @@ pub fn (mut pool PoolProcessor) work_on_pointers(items []voidptr) {
|
||||||
// method in a callback.
|
// method in a callback.
|
||||||
fn process_in_thread(mut pool PoolProcessor, task_id int) {
|
fn process_in_thread(mut pool PoolProcessor, task_id int) {
|
||||||
cb := ThreadCB(pool.thread_cb)
|
cb := ThreadCB(pool.thread_cb)
|
||||||
mut idx := 0
|
|
||||||
ilen := pool.items.len
|
ilen := pool.items.len
|
||||||
for {
|
for {
|
||||||
if pool.ntask >= ilen {
|
idx := int(C.atomic_fetch_add_u32(&pool.ntask, 1))
|
||||||
break
|
|
||||||
}
|
|
||||||
pool.ntask_mtx.@lock()
|
|
||||||
idx = pool.ntask
|
|
||||||
pool.ntask++
|
|
||||||
pool.ntask_mtx.unlock()
|
|
||||||
if idx >= ilen {
|
if idx >= ilen {
|
||||||
break
|
break
|
||||||
}
|
}
|
||||||
|
|
|
@ -3,47 +3,49 @@
|
||||||
// that can be found in the LICENSE file.
|
// that can be found in the LICENSE file.
|
||||||
module sync
|
module sync
|
||||||
|
|
||||||
// WaitGroup implementation. wait() blocks until all tasks complete.
|
[trusted]
|
||||||
|
fn C.atomic_fetch_add_u32(voidptr, u32) u32
|
||||||
|
|
||||||
|
// WaitGroup
|
||||||
// Do not copy an instance of WaitGroup, use a ref instead.
|
// Do not copy an instance of WaitGroup, use a ref instead.
|
||||||
//
|
//
|
||||||
// Two mutexes are required so that wait() doesn't unblock on done()/add() before
|
// usage: in main thread:
|
||||||
// task_count becomes zero.
|
// `wg := sync.new_waitgroup()
|
||||||
|
// `wg.add(nr_jobs)` before starting jobs with `go ...`
|
||||||
|
// `wg.wait()` to wait for all jobs to have finished
|
||||||
|
//
|
||||||
|
// in each parallel job:
|
||||||
|
// `wg.done()` when finished
|
||||||
//
|
//
|
||||||
// [init_with=new_waitgroup] // TODO: implement support for init_with struct attribute, and disallow WaitGroup{} from outside the sync.new_waitgroup() function.
|
// [init_with=new_waitgroup] // TODO: implement support for init_with struct attribute, and disallow WaitGroup{} from outside the sync.new_waitgroup() function.
|
||||||
[ref_only]
|
[ref_only]
|
||||||
struct WaitGroup {
|
struct WaitGroup {
|
||||||
mut:
|
mut:
|
||||||
task_count int // current task count
|
task_count u32 // current task count - reading/writing should be atomic
|
||||||
task_count_mutex Mutex // This mutex protects the task_count count in add()
|
sem Semaphore // This blocks wait() until tast_countreleased by add()
|
||||||
wait_blocker Semaphore // This blocks the wait() until released by add()
|
|
||||||
}
|
}
|
||||||
|
|
||||||
pub fn new_waitgroup() &WaitGroup {
|
pub fn new_waitgroup() &WaitGroup {
|
||||||
mut wg := &WaitGroup{}
|
mut wg := &WaitGroup{}
|
||||||
wg.task_count_mutex.init()
|
wg.init()
|
||||||
wg.wait_blocker.init(1)
|
|
||||||
return wg
|
return wg
|
||||||
}
|
}
|
||||||
|
|
||||||
|
pub fn (mut wg WaitGroup) init() {
|
||||||
|
wg.sem.init(0)
|
||||||
|
}
|
||||||
|
|
||||||
// add increments (+ve delta) or decrements (-ve delta) task count by delta
|
// add increments (+ve delta) or decrements (-ve delta) task count by delta
|
||||||
// and unblocks any wait() calls if task count becomes zero.
|
// and unblocks any wait() calls if task count becomes zero.
|
||||||
// add panics if task count drops below zero.
|
// add panics if task count drops below zero.
|
||||||
pub fn (mut wg WaitGroup) add(delta int) {
|
pub fn (mut wg WaitGroup) add(delta int) {
|
||||||
// protect task_count
|
old_nrjobs := int(C.atomic_fetch_add_u32(&wg.task_count, u32(delta)))
|
||||||
wg.task_count_mutex.@lock()
|
new_nrjobs := old_nrjobs + delta
|
||||||
defer {
|
if new_nrjobs < 0 {
|
||||||
wg.task_count_mutex.unlock()
|
|
||||||
}
|
|
||||||
// If task_count likely to leave zero, set wait() to block
|
|
||||||
if wg.task_count == 0 {
|
|
||||||
wg.wait_blocker.wait()
|
|
||||||
}
|
|
||||||
wg.task_count += delta
|
|
||||||
if wg.task_count < 0 {
|
|
||||||
panic('Negative number of jobs in waitgroup')
|
panic('Negative number of jobs in waitgroup')
|
||||||
}
|
}
|
||||||
if wg.task_count == 0 { // if no more task_count tasks
|
if new_nrjobs == 0 {
|
||||||
wg.wait_blocker.post() // unblock wait()
|
wg.sem.post()
|
||||||
}
|
}
|
||||||
}
|
}
|
||||||
|
|
||||||
|
@ -54,6 +56,5 @@ pub fn (mut wg WaitGroup) done() {
|
||||||
|
|
||||||
// wait blocks until all tasks are done (task count becomes zero)
|
// wait blocks until all tasks are done (task count becomes zero)
|
||||||
pub fn (mut wg WaitGroup) wait() {
|
pub fn (mut wg WaitGroup) wait() {
|
||||||
wg.wait_blocker.wait() // blocks until task_count becomes 0
|
wg.sem.wait() // blocks until task_count becomes 0
|
||||||
wg.wait_blocker.post() // allow other wait()s to unblock or reuse wait group
|
|
||||||
}
|
}
|
||||||
|
|
Loading…
Reference in New Issue