[tsan] Don't delay SIGTRAP handler

[vitalybuka]

remove unneeded final trap

[vitalybuka]

fix handle_sigtrap value

[eugenis]

LGTM

[stevewan]

Hi @vitalybuka,

This is causing LIT failures in clang-s390x-linux. Can you please take a look? Thanks!

Steven

compiler-rt/lib/tsan/rtl/tsan_interceptors_posix.cpp

 #else
 const int PTHREAD_MUTEX_RECURSIVE = 2;
 const int PTHREAD_MUTEX_RECURSIVE_NP = 2;
 #endif
 #if !SANITIZER_FREEBSD && !SANITIZER_MAC && !SANITIZER_NETBSD
 const int EPOLL_CTL_ADD = 1;
 #endif
 const int SIGILL = 4;
+const int SIGTRAP = 5;
 const int SIGABRT = 6;
 const int SIGFPE = 8;
 const int SIGSEGV = 11;
 const int SIGPIPE = 13;
 const int SIGTERM = 15;
 #if defined(__mips__) || SANITIZER_FREEBSD || SANITIZER_MAC || SANITIZER_NETBSD
 const int SIGBUS = 10;
 const int SIGSYS = 12;
void ProcessPendingSignals(ThreadState *thr) {
   res = REAL(pthread_sigmask)(SIG_SETMASK, &sctx->oldset, 0);
   CHECK_EQ(res, 0);
   atomic_fetch_add(&thr->in_signal_handler, -1, memory_order_relaxed);
 }
 
 }  // namespace __tsan
 
 static bool is_sync_signal(ThreadSignalContext *sctx, int sig) {
-  return sig == SIGSEGV || sig == SIGBUS || sig == SIGILL ||
+  return sig == SIGSEGV || sig == SIGBUS || sig == SIGILL || sig == SIGTRAP ||
          sig == SIGABRT || sig == SIGFPE || sig == SIGPIPE || sig == SIGSYS ||
          // If we are sending signal to ourselves, we must process it now.
          (sctx && sig == sctx->int_signal_send);
 }
 
 void ALWAYS_INLINE rtl_generic_sighandler(bool sigact, int sig,
                                           __sanitizer_siginfo *info,
                                           void *ctx) {
   cur_thread_init();
   ThreadState *thr = cur_thread();
   ThreadSignalContext *sctx = SigCtx(thr);

compiler-rt/test/sanitizer_common/TestCases/Linux/signal_trap_handler.cpp

+// RUN: %clangxx -O1 %s -o %t && %env_tool_opts=handle_sigtrap=1 %run %t 2>&1 | FileCheck %s
+
+#include <assert.h>
+#include <signal.h>
+#include <stdio.h>
+
+int handled;
+
+void handler(int signo, siginfo_t *info, void *uctx) {
+  handled = 1;
+}
+
+int main() {
+  struct sigaction a = {}, old = {};
+  a.sa_sigaction = handler;
+  a.sa_flags = SA_SIGINFO;
+  sigaction(SIGTRAP, &a, &old);
+
+  a = {};
+  sigaction(SIGTRAP, 0, &a);
+  assert(a.sa_sigaction == handler);
+  assert(a.sa_flags & SA_SIGINFO);
+
+  __builtin_debugtrap();
+  assert(handled);
+  fprintf(stderr, "HANDLED %d\n", handled);
+}
+
+// CHECK: HANDLED 1