commit 7a829a85638571abcf62b284fc0f884aaeb5d428
author Harald Alvestrand <hta@webrtc.org> Wed Feb 12 06:38:21 2020
committer Commit Bot <commit-bot@chromium.org> Wed Feb 12 08:34:12 2020
tree a69d0fcba2c9c49355cf5ce0a3fcbc9a13c5d2d0
parent bc1750d52b93da9651c0247cf64d5e0155ca281f

Sort threading for sctp_mid_ variable

Split the sctp_mid_ variable into two variables,
sctp_mid_n_ and sctp_mid_s_, each of which is only accessed
by one thread.

Bug: webrtc:9987
Change-Id: I4dce944b920f4698e2606a7b85776791cbf55c28
Reviewed-on: https://webrtc-review.googlesource.com/c/src/+/168243
Commit-Queue: Harald Alvestrand <hta@webrtc.org>
Reviewed-by: Karl Wiberg <kwiberg@webrtc.org>
Cr-Commit-Position: refs/heads/master@{#30503}

pc/peer_connection.h

diff --git a/pc/peer_connection.h b/pc/peer_connection.h
index 475029a..822930b 100644
--- a/pc/peer_connection.h
+++ b/pc/peer_connection.h
@@ -321,7 +321,7 @@
   void RequestUsagePatternReportForTesting();
   absl::optional<std::string> sctp_mid() {
     RTC_DCHECK_RUN_ON(signaling_thread());
-    return sctp_mid_;
+    return sctp_mid_s_;
   }
 
  protected:
@@ -1330,9 +1330,11 @@
   // Note: this is used as the data channel MID by both SCTP and data channel
   // transports.  It is set when either transport is initialized and unset when
   // both transports are deleted.
-  absl::optional<std::string>
-      sctp_mid_;  // TODO(bugs.webrtc.org/9987): Accessed on both signaling
-                  // and network thread.
+  // There is one copy on the signaling thread and another copy on the
+  // networking thread. Changes are always initiated from the signaling
+  // thread, but applied first on the networking thread via an invoke().
+  absl::optional<std::string> sctp_mid_s_ RTC_GUARDED_BY(signaling_thread());
+  absl::optional<std::string> sctp_mid_n_ RTC_GUARDED_BY(network_thread());
 
   // Whether this peer is the caller. Set when the local description is applied.
   absl::optional<bool> is_caller_ RTC_GUARDED_BY(signaling_thread());