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let initOnce take a shared Mutex #5661

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Merged
dlang-bot merged 2 commits into from
Sep 14, 2017
Merged

let initOnce take a shared Mutex #5661

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82fe75f
let initOnce take a shared Mutex
aG0aep6G Jul 28, 2017
0123ea9
don't deprecate initOnce with unshared Mutex
aG0aep6G Sep 2, 2017
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24 changes: 15 additions & 9 deletions std/concurrency.d
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Original file line number Diff line number Diff line change
Expand Up @@ -2390,15 +2390,15 @@ version (unittest)
}
}

private @property Mutex initOnceLock()
private @property shared(Mutex) initOnceLock()
{
__gshared Mutex lock;
if (auto mtx = cast() atomicLoad!(MemoryOrder.acq)(*cast(shared)&lock))
static shared Mutex lock;
if (auto mtx = atomicLoad!(MemoryOrder.acq)(lock))
return mtx;
auto mtx = new Mutex;
if (cas(cast(shared)&lock, cast(shared) null, cast(shared) mtx))
auto mtx = new shared Mutex;
if (cas(&lock, cast(shared) null, mtx))
return mtx;
return cast() atomicLoad!(MemoryOrder.acq)(*cast(shared)&lock);
return atomicLoad!(MemoryOrder.acq)(lock);
}

/**
Expand Down Expand Up @@ -2476,7 +2476,7 @@ auto ref initOnce(alias var)(lazy typeof(var) init)
* Returns:
* A reference to the initialized variable
*/
auto ref initOnce(alias var)(lazy typeof(var) init, Mutex mutex)
auto ref initOnce(alias var)(lazy typeof(var) init, shared Mutex mutex)
{
// check that var is global, can't take address of a TLS variable
static assert(is(typeof({ __gshared p = &var; })),
Expand All @@ -2498,14 +2498,20 @@ auto ref initOnce(alias var)(lazy typeof(var) init, Mutex mutex)
return var;
}

/// ditto
auto ref initOnce(alias var)(lazy typeof(var) init, Mutex mutex)
{
return initOnce!var(init, cast(shared) mutex);
}

/// Use a separate mutex when init blocks on another thread that might also call initOnce.
@system unittest
{
import core.sync.mutex : Mutex;

static shared bool varA, varB;
__gshared Mutex m;
m = new Mutex;
static shared Mutex m;
m = new shared Mutex;

spawn({
// use a different mutex for varB to avoid a dead-lock
Expand Down