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Only do PHAsset metadata requests one at a time to workaround Photos framework deadlock

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This commit is contained in:
Adlai Holler
2015-10-05 21:05:27 -07:00
parent 2e5da5599d
commit d94dcdef0f
1 changed files with 19 additions and 3 deletions
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22
AsyncDisplayKit/ASMultiplexImageNode.mm
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@@ -518,17 +518,33 @@ typedef void(^ASMultiplexImageLoadCompletionBlock)(UIImage *image, id imageIdent
ASDisplayNodeAssertNotNil(request, @"request is required");
ASDisplayNodeAssertNotNil(completionBlock, @"completionBlock is required");
/*
* Locking rationale:
* As of iOS 9, Photos.framework will eventually deadlock if you hit it with concurrent fetch requests. rdar://22984886
* Image requests are OK, but metadata requests aren't, so we limit ourselves to one at a time.
* -[PHFetchResult dealloc] plays a role in this deadlock, so we help the fetch result die ASAP by never storing it.
*/
static NSLock *phRequestLock;
static dispatch_once_t onceToken;
dispatch_once(&onceToken, ^{
phRequestLock = [NSLock new];
});
// This is sometimes called on main but there's no reason to stay there
dispatch_async(dispatch_get_global_queue(QOS_CLASS_DEFAULT, 0), ^{
// Get the PHAsset itself.
PHFetchResult *assetFetchResult = [PHAsset fetchAssetsWithLocalIdentifiers:@[request.assetIdentifier] options:nil];
if ([assetFetchResult count] == 0) {
[phRequestLock lock];
PHAsset *imageAsset = [PHAsset fetchAssetsWithLocalIdentifiers:@[request.assetIdentifier] options:nil].firstObject;
[phRequestLock unlock];
if (imageAsset == nil) {
// Error.
completionBlock(nil, nil);
return;
}
PHAsset *imageAsset = [assetFetchResult firstObject];
PHImageRequestOptions *options = [request.options copy];
// We don't support opportunistic delivery – one request, one image.