Do init_profile_extras constructor tasks only once
Bug: http://b/116873221
Currently, every coverage-enabled binary (the main executable or shared
library) in the process executes the init_profile_extras constructor
leading to redundant initialization.
Instead, add a weak global value that gets set once so following
constructors don't set a signal handler or create a pthread. It's ok to
do this before the constructor succeeds because if pthread creation or
signal handler registration failed once, they are unlikely to succeed
the second time.
This is thread-safe since constructor initialization is single-threaded.
The one possibility for a race - the process doesn't have any
coverage-enabled library, and multiple threads dlopen() coverage-enabled
shared libraries - seems quite unlikely.
Test: Verify that only one extra thread is created for a daemon (adbd).
Change-Id: Ie969311c2ddac147497c870b5c365b4617b3c60a
diff --git a/toolchain-extras/profile-extras.cpp b/toolchain-extras/profile-extras.cpp
index 2d68508..f999a6b 100644
--- a/toolchain-extras/profile-extras.cpp
+++ b/toolchain-extras/profile-extras.cpp
@@ -67,6 +67,8 @@
}
}
+__attribute__((weak)) int init_profile_extras_once = 0;
+
// Initialize libprofile-extras:
// - Install a signal handler that triggers __gcov_flush on <GCOV_FLUSH_SIGNAL>.
// - Create a thread that calls __gcov_flush when <kCoveragePropName> sysprop
@@ -81,6 +83,10 @@
// We force the linker to include init_profile_extras() by passing
// '-uinit_profile_extras' to the linker (in build/soong).
__attribute__((constructor)) int init_profile_extras(void) {
+ if (init_profile_extras_once)
+ return 0;
+ init_profile_extras_once = 1;
+
sighandler_t ret1 = signal(GCOV_FLUSH_SIGNAL, gcov_signal_handler);
if (ret1 == SIG_ERR) {
return -1;
