[Runtime] Don't enable tracing in logd, diagnosticd, notifyd.

We can't use os_log functionality in logd, diagnosticd, or notifyd. Check for them and disable tracing in those processes.

Add a new TracingCommon.h for common code shared between swiftCore and swift_Concurrency tracing. Add a single function that checks if tracing should be enabled, which now checks if os_signpost_enabled is available, and if the process is one of these. Modify the tracing code to check this before creating os_log objects.

rdar://124226334

Author: mikeash

include/swift/Runtime/TracingCommon.h

@@ -0,0 +1,47 @@
+//===--- TracingCommon.h - Common code for runtime/Concurrency -----*- C++ -*-//
+//
+// This source file is part of the Swift.org open source project
+//
+// Copyright (c) 2014 - 2021 Apple Inc. and the Swift project authors
+// Licensed under Apache License v2.0 with Runtime Library Exception
+//
+// See https://swift.org/LICENSE.txt for license information
+// See https://swift.org/CONTRIBUTORS.txt for the list of Swift project authors
+//
+//===----------------------------------------------------------------------===//
+//
+// Support code shared between swiftCore and swift_Concurrency.
+//
+//===----------------------------------------------------------------------===//
+
+#ifndef SWIFT_TRACING_COMMON_H
+#define SWIFT_TRACING_COMMON_H
+
+#if SWIFT_STDLIB_TRACING
+
+#include "swift/Runtime/Config.h"
+#include <os/signpost.h>
+
+extern const char *__progname;
+
+namespace swift {
+namespace runtime {
+namespace trace {
+
+static inline bool shouldEnableTracing() {
+  if (!SWIFT_RUNTIME_WEAK_CHECK(os_signpost_enabled))
+    return false;
+  if (__progname && (strcmp(__progname, "logd") == 0 ||
+                     strcmp(__progname, "diagnosticd") == 0 ||
+                     strcmp(__progname, "notifyd") == 0))
+    return false;
+  return true;
+}
+
+} // namespace trace
+} // namespace runtime
+} // namespace swift
+
+#endif
+
+#endif // SWIFT_TRACING_H

stdlib/public/Concurrency/TracingSignpost.cpp

@@ -17,6 +17,7 @@
 #if SWIFT_STDLIB_CONCURRENCY_TRACING
 
 #include "TracingSignpost.h"
+#include "swift/Runtime/TracingCommon.h"
 #include <stdio.h>
 
 #define SWIFT_LOG_CONCURRENCY_SUBSYSTEM "com.apple.swift.concurrency"
@@ -30,8 +31,15 @@ namespace trace {
 os_log_t ActorLog;
 os_log_t TaskLog;
 swift::once_t LogsToken;
+bool TracingEnabled;
 
 void setupLogs(void *unused) {
+  if (!swift::runtime::trace::shouldEnableTracing()) {
+    TracingEnabled = false;
+    return;
+  }
+
+  TracingEnabled = true;
   ActorLog = os_log_create(SWIFT_LOG_CONCURRENCY_SUBSYSTEM,
                            SWIFT_LOG_ACTOR_CATEGORY);
   TaskLog = os_log_create(SWIFT_LOG_CONCURRENCY_SUBSYSTEM,

stdlib/public/Concurrency/TracingSignpost.h

@@ -70,6 +70,7 @@ namespace trace {
 extern os_log_t ActorLog;
 extern os_log_t TaskLog;
 extern swift::once_t LogsToken;
+extern bool TracingEnabled;
 
 void setupLogs(void *unused);
 
@@ -78,9 +79,9 @@ void setupLogs(void *unused);
 // optimized out.
 #define ENSURE_LOGS(...)                                                       \
   do {                                                                         \
-    if (!SWIFT_RUNTIME_WEAK_CHECK(os_signpost_enabled))                        \
-      return __VA_ARGS__;                                                      \
     swift::once(LogsToken, setupLogs, nullptr);                                \
+    if (!TracingEnabled)                                                       \
+      return __VA_ARGS__;                                                      \
   } while (0)
 
 // Every function does ENSURE_LOGS() before making any os_signpost calls, so

stdlib/public/runtime/Tracing.cpp

@@ -15,6 +15,7 @@
 //===----------------------------------------------------------------------===//
 
 #include "Tracing.h"
+#include "swift/Runtime/TracingCommon.h"
 
 #if SWIFT_STDLIB_TRACING
 
@@ -27,8 +28,15 @@ namespace trace {
 
 os_log_t ScanLog;
 swift::once_t LogsToken;
+bool TracingEnabled;
 
 void setupLogs(void *unused) {
+  if (!shouldEnableTracing()) {
+    TracingEnabled = false;
+    return;
+  }
+
+  TracingEnabled = true;
   ScanLog = os_log_create(SWIFT_LOG_SUBSYSTEM, SWIFT_LOG_SECTION_SCAN_CATEGORY);
 }
 

stdlib/public/runtime/Tracing.h

@@ -34,6 +34,7 @@ namespace trace {
 
 extern os_log_t ScanLog;
 extern swift::once_t LogsToken;
+extern bool TracingEnabled;
 
 void setupLogs(void *unused);
 
@@ -48,9 +49,9 @@ void setupLogs(void *unused);
 // optimized out.
 #define ENSURE_LOG(log)                                                        \
   do {                                                                         \
-    if (!SWIFT_RUNTIME_WEAK_CHECK(os_signpost_enabled))                        \
-      return {};                                                               \
     swift::once(LogsToken, setupLogs, nullptr);                                \
+    if (!TracingEnabled)                                                       \
+      return {};                                                               \
   } while (0)
 
 /// A struct that captures the state of a scan tracing signpost. When the scan