Merge pull request #80018 from mikeash/eager-tracing-non-platform-binaries

[Runtime] Only use lazy os_signpost initialization for platform binaries.

Author: mikeash

include/swift/Runtime/TracingCommon.h

@@ -19,6 +19,7 @@
 
 #if SWIFT_STDLIB_TRACING
 
+#include "swift/Basic/Lazy.h"
 #include "swift/Runtime/Config.h"
 #include <os/signpost.h>
 
@@ -35,24 +36,51 @@ 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 ||
-                     strcmp(__progname, "xpcproxy") == 0 ||
-                     strcmp(__progname, "logd_helper") == 0))
-    return false;
   return true;
 }
 
-static inline bool tracingReady() {
 #if SWIFT_USE_OS_TRACE_LAZY_INIT
+#if __has_include(<sys/codesign.h>)
+#include <sys/codesign.h>
+#else
+// SPI
+#define CS_OPS_STATUS 0
+#define CS_PLATFORM_BINARY 0x04000000
+extern "C" int csops(pid_t, unsigned int, void *, size_t);
+#endif
+
+#include <unistd.h>
+
+static inline bool isPlatformBinary() {
+  unsigned int flags = 0;
+  int error = csops(getpid(), CS_OPS_STATUS, &flags, sizeof(flags));
+  if (error)
+    return true; // Fail safe if the call fails, assume it's a platform binary.
+  return (flags & CS_PLATFORM_BINARY) != 0;
+}
+
+static inline bool tracingReady() {
+  // For non-platform binaries, consider tracing to always be ready. We can
+  // safely initiate setup if it isn't.
+  bool platformBinary = SWIFT_LAZY_CONSTANT(isPlatformBinary());
+  if (!platformBinary)
+    return true;
+
+  // For platform binaries, we may be on the path that sets up tracing, and
+  // making tracing calls may deadlock in that case. Wait until something else
+  // set up tracing before using it.
   if (!_os_trace_lazy_init_completed_4swift())
     return false;
-#endif
 
   return true;
 }
 
+#else
+
+static inline bool tracingReady() { return true; }
+
+#endif
+
 } // namespace trace
 } // namespace runtime
 } // namespace swift