[compiler-rt] r219675 - tsan: refactor atexit handling
Dmitry Vyukov
dvyukov at google.com
Tue Oct 14 02:32:46 PDT 2014
Author: dvyukov
Date: Tue Oct 14 04:32:45 2014
New Revision: 219675
URL: http://llvm.org/viewvc/llvm-project?rev=219675&view=rev
Log:
tsan: refactor atexit handling
The current handling (manual execution of atexit callbacks)
is overly complex and leads to constant problems due to mutual ordering of callbacks.
Instead simply wrap callbacks into our wrapper to establish
the necessary synchronization.
Fixes issue https://code.google.com/p/thread-sanitizer/issues/detail?id=80
Added:
compiler-rt/trunk/test/tsan/dlclose.cc
Modified:
compiler-rt/trunk/lib/tsan/rtl/tsan_interceptors.cc
Modified: compiler-rt/trunk/lib/tsan/rtl/tsan_interceptors.cc
URL: http://llvm.org/viewvc/llvm-project/compiler-rt/trunk/lib/tsan/rtl/tsan_interceptors.cc?rev=219675&r1=219674&r2=219675&view=diff
==============================================================================
--- compiler-rt/trunk/lib/tsan/rtl/tsan_interceptors.cc (original)
+++ compiler-rt/trunk/lib/tsan/rtl/tsan_interceptors.cc Tue Oct 14 04:32:45 2014
@@ -105,11 +105,6 @@ typedef void (*sighandler_t)(int sig);
#define errno (*__errno_location())
-// 16K loaded modules should be enough for everyone.
-static const uptr kMaxModules = 1 << 14;
-static LoadedModule *modules;
-static uptr nmodules;
-
struct sigaction_t {
union {
sighandler_t sa_handler;
@@ -289,6 +284,7 @@ TSAN_INTERCEPTOR(int, nanosleep, void *r
return res;
}
+/*
class AtExitContext {
public:
AtExitContext()
@@ -346,6 +342,26 @@ class AtExitContext {
};
static AtExitContext *atexit_ctx;
+*/
+
+// The sole reason tsan wraps atexit callbacks is to establish synchronization
+// between callback setup and callback execution.
+struct AtExitCtx {
+ void (*f)();
+ void *arg;
+};
+
+static void at_exit_wrapper(void *arg) {
+ ThreadState *thr = cur_thread();
+ uptr pc = 0;
+ Acquire(thr, pc, (uptr)arg);
+ AtExitCtx *ctx = (AtExitCtx*)arg;
+ ((void(*)(void *arg))ctx->f)(ctx->arg);
+ __libc_free(ctx);
+}
+
+static int setup_at_exit_wrapper(ThreadState *thr, uptr pc, void(*f)(),
+ void *arg, void *dso);
TSAN_INTERCEPTOR(int, atexit, void (*f)()) {
if (cur_thread()->in_symbolizer)
@@ -353,40 +369,51 @@ TSAN_INTERCEPTOR(int, atexit, void (*f)(
// We want to setup the atexit callback even if we are in ignored lib
// or after fork.
SCOPED_INTERCEPTOR_RAW(atexit, f);
- return atexit_ctx->atexit(thr, pc, false, (void(*)())f, 0, 0);
+ return setup_at_exit_wrapper(thr, pc, (void(*)())f, 0, 0);
}
-TSAN_INTERCEPTOR(int, on_exit, void(*f)(int, void*), void *arg) {
+TSAN_INTERCEPTOR(int, __cxa_atexit, void (*f)(void *a), void *arg, void *dso) {
if (cur_thread()->in_symbolizer)
return 0;
- SCOPED_TSAN_INTERCEPTOR(on_exit, f, arg);
- return atexit_ctx->atexit(thr, pc, true, (void(*)())f, arg, 0);
+ SCOPED_TSAN_INTERCEPTOR(__cxa_atexit, f, arg, dso);
+ return setup_at_exit_wrapper(thr, pc, (void(*)())f, arg, dso);
}
-bool IsSaticModule(void *dso) {
- if (modules == 0)
- return false;
- for (uptr i = 0; i < nmodules; i++) {
- if (modules[i].containsAddress((uptr)dso))
- return true;
- }
- return false;
+static int setup_at_exit_wrapper(ThreadState *thr, uptr pc, void(*f)(),
+ void *arg, void *dso) {
+ AtExitCtx *ctx = (AtExitCtx*)__libc_malloc(sizeof(AtExitCtx));
+ ctx->f = f;
+ ctx->arg = arg;
+ Release(thr, pc, (uptr)ctx);
+ // Memory allocation in __cxa_atexit will race with free during exit,
+ // because we do not see synchronization around atexit callback list.
+ ThreadIgnoreBegin(thr, pc);
+ int res = REAL(__cxa_atexit)(at_exit_wrapper, ctx, dso);
+ ThreadIgnoreEnd(thr, pc);
+ return res;
}
-TSAN_INTERCEPTOR(int, __cxa_atexit, void (*f)(void *a), void *arg, void *dso) {
+static void on_exit_wrapper(int status, void *arg) {
+ ThreadState *thr = cur_thread();
+ uptr pc = 0;
+ Acquire(thr, pc, (uptr)arg);
+ AtExitCtx *ctx = (AtExitCtx*)arg;
+ ((void(*)(int status, void *arg))ctx->f)(status, ctx->arg);
+ __libc_free(ctx);
+}
+
+TSAN_INTERCEPTOR(int, on_exit, void(*f)(int, void*), void *arg) {
if (cur_thread()->in_symbolizer)
return 0;
- SCOPED_TSAN_INTERCEPTOR(__cxa_atexit, f, arg, dso);
- // If it's the main executable or a statically loaded library,
- // we will call the callback.
- if (dso == 0 || IsSaticModule(dso))
- return atexit_ctx->atexit(thr, pc, false, (void(*)())f, arg, dso);
-
- // Dynamically load module, don't know when to call the callback for it.
+ SCOPED_TSAN_INTERCEPTOR(on_exit, f, arg);
+ AtExitCtx *ctx = (AtExitCtx*)__libc_malloc(sizeof(AtExitCtx));
+ ctx->f = (void(*)())f;
+ ctx->arg = arg;
+ Release(thr, pc, (uptr)ctx);
// Memory allocation in __cxa_atexit will race with free during exit,
// because we do not see synchronization around atexit callback list.
ThreadIgnoreBegin(thr, pc);
- int res = REAL(__cxa_atexit)(f, arg, dso);
+ int res = REAL(on_exit)(on_exit_wrapper, ctx);
ThreadIgnoreEnd(thr, pc);
return res;
}
@@ -2244,8 +2271,6 @@ namespace __tsan {
static void finalize(void *arg) {
ThreadState *thr = cur_thread();
- uptr pc = 0;
- atexit_ctx->exit(thr, pc);
int status = Finalize(thr);
// Make sure the output is not lost.
// Flushing all the streams here may freeze the process if a child thread is
@@ -2433,9 +2458,6 @@ void InitializeInterceptors() {
// Need to setup it, because interceptors check that the function is resolved.
// But atexit is emitted directly into the module, so can't be resolved.
REAL(atexit) = (int(*)(void(*)()))unreachable;
- atexit_ctx = new(internal_alloc(MBlockAtExit, sizeof(AtExitContext)))
- AtExitContext();
-
if (REAL(__cxa_atexit)(&finalize, 0, 0)) {
Printf("ThreadSanitizer: failed to setup atexit callback\n");
Die();
@@ -2447,11 +2469,6 @@ void InitializeInterceptors() {
}
FdInit();
-
- // Remember list of loaded libraries for atexit interceptors.
- modules = (LoadedModule*)MmapOrDie(sizeof(*modules)*kMaxModules,
- "LoadedModule");
- nmodules = GetListOfModules(modules, kMaxModules, 0);
}
void *internal_start_thread(void(*func)(void *arg), void *arg) {
Added: compiler-rt/trunk/test/tsan/dlclose.cc
URL: http://llvm.org/viewvc/llvm-project/compiler-rt/trunk/test/tsan/dlclose.cc?rev=219675&view=auto
==============================================================================
--- compiler-rt/trunk/test/tsan/dlclose.cc (added)
+++ compiler-rt/trunk/test/tsan/dlclose.cc Tue Oct 14 04:32:45 2014
@@ -0,0 +1,56 @@
+// RUN: %clangxx_tsan -O1 %s -DBUILD_SO -fPIC -shared -o %t-so.so
+// RUN: %clangxx_tsan -O1 %s -o %t && %run %t 2>&1 | FileCheck %s
+
+// Test case for
+// https://code.google.com/p/thread-sanitizer/issues/detail?id=80
+
+#ifdef BUILD_SO
+
+#include <stdio.h>
+
+extern "C"
+void sofunc() {
+ fprintf(stderr, "HELLO FROM SO\n");
+}
+
+#else // BUILD_SO
+
+#include <dlfcn.h>
+#include <stdio.h>
+#include <stddef.h>
+#include <unistd.h>
+#include <string>
+
+void *lib;
+void *lib2;
+
+struct Closer {
+ ~Closer() {
+ dlclose(lib);
+ fprintf(stderr, "CLOSED SO\n");
+ }
+};
+static Closer c;
+
+int main(int argc, char *argv[]) {
+ lib = dlopen((std::string(argv[0]) + std::string("-so.so")).c_str(),
+ RTLD_NOW|RTLD_NODELETE);
+ if (lib == 0) {
+ printf("error in dlopen: %s\n", dlerror());
+ return 1;
+ }
+ void *f = dlsym(lib, "sofunc");
+ if (f == 0) {
+ printf("error in dlsym: %s\n", dlerror());
+ return 1;
+ }
+ ((void(*)())f)();
+ return 0;
+}
+
+#endif // BUILD_SO
+
+// CHECK: HELLO FROM SO
+// CHECK-NOT: Inconsistency detected by ld.so
+// CHECK: CLOSED SO
+
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