Backed out 2 changesets (bug 1674773) for turning Bug 1646925 into almost permafail.

Backed out changeset acd441508a66 (bug 1674773)
Backed out changeset 89babec1b885 (bug 1674773)

browser/config/mozconfigs/linux64/tsan

@@ -18,6 +18,9 @@ export MOZ_PKG_SPECIAL=tsan
 # Disable telemetry
 ac_add_options MOZ_TELEMETRY_REPORTING=
 
+# Ensure Rust also gets the necessary instrumentation
+export RUSTFLAGS="-Zsanitizer=thread"
+
 # rustfmt is currently missing in Rust nightly
 unset RUSTFMT
 

config/makefiles/rust.mk

@@ -53,11 +53,6 @@ ifeq (1,$(MOZ_PARALLEL_BUILD))
 cargo_build_flags += -j1
 endif
 
-# This should also be paired with -Zbuild-std, but that doesn't work yet.
-ifdef MOZ_TSAN
-RUSTFLAGS += -Zsanitizer=thread
-endif
-
 # These flags are passed via `cargo rustc` and only apply to the final rustc
 # invocation (i.e., only the top-level crate, not its dependencies).
 cargo_rustc_flags = $(CARGO_RUSTCFLAGS)

taskcluster/ci/spidermonkey/linux.yml

@@ -237,7 +237,7 @@ sm-tsan-linux64/opt:
         toolchain:
             - linux64-binutils
             - linux64-clang
-            - linux64-rust-nightly
+            - linux64-rust
             - linux64-dump-syms
 
 sm-rootanalysis-linux64/debug:

toolkit/library/gtest/rust/Cargo.toml

@@ -35,7 +35,6 @@ glean = ["gkrust-shared/glean", "fog-gtest"]
 glean_with_gecko = ["gkrust-shared/glean_with_gecko", "fog-gtest"]
 rust_fxa_client = ["gkrust-shared/rust_fxa_client"]
 with_dbus = ["gkrust-shared/with_dbus"]
-thread_sanitizer = ["gkrust-shared/thread_sanitizer"]
 
 [dependencies]
 bench-collections-gtest = { path = "../../../../xpcom/rust/gtest/bench-collections" }

toolkit/library/rust/Cargo.toml

@@ -36,7 +36,6 @@ glean = ["gkrust-shared/glean"]
 glean_with_gecko = ["gkrust-shared/glean_with_gecko"]
 rust_fxa_client = ["gkrust-shared/rust_fxa_client"]
 with_dbus = ["gkrust-shared/with_dbus"]
-thread_sanitizer = ["gkrust-shared/thread_sanitizer"]
 
 [dependencies]
 gkrust-shared = { path = "shared" }

toolkit/library/rust/gkrust-features.mozbuild

@@ -12,9 +12,6 @@ if CONFIG['MOZ_DEBUG']:
         'gecko_refcount_logging',
     ]
 
-if CONFIG['MOZ_TSAN']:
-    gkrust_features += ['thread_sanitizer']
-
 gkrust_features += ['quantum_render', 'webgpu']
 if CONFIG['MOZ_WEBRENDER_DEBUGGER']:
     gkrust_features += ['webrender_debugger']

toolkit/library/rust/shared/Cargo.toml

@@ -108,7 +108,6 @@ glean = ["fog_control"]
 glean_with_gecko = ["fog_control/with_gecko"]
 rust_fxa_client = ["firefox-accounts-bridge"]
 with_dbus = ["audio_thread_priority/with_dbus"]
-thread_sanitizer = ["xpcom/thread_sanitizer"]
 
 [lib]
 path = "lib.rs"

xpcom/rust/xpcom/Cargo.toml

@@ -11,6 +11,3 @@ nserror = { path = "../nserror" }
 threadbound = "0.1"
 xpcom_macros = { path = "xpcom_macros" }
 thin-vec = { version = "0.2.1", features = ["gecko-ffi"] }
-
-[features]
-thread_sanitizer = []

xpcom/rust/xpcom/src/refptr.rs

@@ -298,18 +298,8 @@ impl AtomicRefcnt {
     pub unsafe fn dec(&self) -> nsrefcnt {
         let result = self.0.fetch_sub(1, Ordering::Release) as nsrefcnt - 1;
         if result == 0 {
-            // We're going to destroy the object on this thread, so we need
-            // acquire semantics to synchronize with the memory released by
-            // the last release on other threads, that is, to ensure that
-            // writes prior to that release are now visible on this thread.
-            if cfg!(feature = "thread_sanitizer") {
-                // TSan doesn't understand atomic::fence, so in order to avoid
-                // a false positive for every time a refcounted object is
-                // deleted, we replace the fence with an atomic operation.
-                self.0.load(Ordering::Acquire);
-            } else {
-                atomic::fence(Ordering::Acquire);
-            }
+            // We're going to destroy the object on this thread.
+            atomic::fence(Ordering::Acquire);
         }
         result
     }