Update GPBMessage.m
Fix up some spelling/grammar.
diff --git a/objectivec/GPBMessage.m b/objectivec/GPBMessage.m
index 9efef70..1d26392 100644
--- a/objectivec/GPBMessage.m
+++ b/objectivec/GPBMessage.m
@@ -80,18 +80,17 @@
GPBFieldDescriptor *autocreatorField_;
GPBExtensionDescriptor *autocreatorExtension_;
- // Message can only be mutated from one thread. But some *readonly* operations modify internal
+ // Messages can only be mutated from one thread. But some *readonly* operations modify internal
// state because they autocreate things. The autocreatedExtensionMap_ is one such structure.
- // Access during readonly operations is protected via this semaphore.
+ // Access during readonly operations is protected via this lock.
//
- // Long ago, this was a OSSpinLock, but then it came to light that there were issues for that on
+ // Long ago, this was an OSSpinLock, but then it came to light that there were issues for that on
// iOS:
// http://mjtsai.com/blog/2015/12/16/osspinlock-is-unsafe/
// https://lists.swift.org/pipermail/swift-dev/Week-of-Mon-20151214/000372.html
- // So it was a dispatch_semaphore_t, but that has issues with priority inversion if developer code
- // uses queue for different things. But the minOS versions are now high enough, os_unfair_lock and
- // be used, and should provide all the support needed. For more information in the
- // concurrence/locking space see:
+ // It was changed to a dispatch_semaphore_t, but that has potential for priority inversion issues.
+ // The minOS versions are now high enough that os_unfair_lock can be used, and should provide
+ // all the support we need. For more information in the concurrency/locking space see:
// https://gist.github.com/tclementdev/6af616354912b0347cdf6db159c37057
// https://developer.apple.com/library/archive/documentation/Performance/Conceptual/EnergyGuide-iOS/PrioritizeWorkWithQoS.html
// https://developer.apple.com/videos/play/wwdc2017/706/
