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-rw-r--r--absl/base/thread_annotations.h12
1 files changed, 11 insertions, 1 deletions
diff --git a/absl/base/thread_annotations.h b/absl/base/thread_annotations.h
index fbb2797..2241ace 100644
--- a/absl/base/thread_annotations.h
+++ b/absl/base/thread_annotations.h
@@ -108,13 +108,23 @@
// The mutex is expected to be held both on entry to, and exit from, the
// function.
//
+// An exclusive lock allows read-write access to the guarded data member(s), and
+// only one thread can acquire a lock exclusively at any one time. A shared lock
+// allows read-only access, and any number of threads can acquire a shared lock
+// concurrently.
+//
+// Generally, non-const methods should be annotated with
+// EXCLUSIVE_LOCKS_REQUIRED, while const methods should be annotated with
+// SHARED_LOCKS_REQUIRED.
+//
// Example:
//
// Mutex mu1, mu2;
// int a GUARDED_BY(mu1);
// int b GUARDED_BY(mu2);
//
-// void foo() EXCLUSIVE_LOCKS_REQUIRED(mu1, mu2) { ... };
+// void foo() EXCLUSIVE_LOCKS_REQUIRED(mu1, mu2) { ... }
+// void bar() const SHARED_LOCKS_REQUIRED(mu1, mu2) { ... }
#define EXCLUSIVE_LOCKS_REQUIRED(...) \
THREAD_ANNOTATION_ATTRIBUTE__(exclusive_locks_required(__VA_ARGS__))