Improve crash handler

- Added two other signals, that generate a core dump by default to
  the crash handler: SIGQUIT and SIGSYS.
- Sending SIGABORT to processes in the same group would generate a
  core dump of another process - using SIGTERM now.
- Setup alternate signal stack only once and hence allocate the
  memory only once (there can be only one alternate signal stack)

Change-Id: I861505668dc2484730ec79410612f55698b695c4
Reviewed-by: Robert Griebl <robert.griebl@qt.io>

2 files changed, 27 insertions, 23 deletions

diff --git a/src/common-lib/crashhandler.cpp b/src/common-lib/crashhandler.cpp
index 22683612..9b2db648 100644
--- a/src/common-lib/crashhandler.cpp
+++ b/src/common-lib/crashhandler.cpp
@@ -326,7 +326,7 @@ static void initBacktraceUnix()
 #  endif
 
     UnixSignalHandler::instance()->install(UnixSignalHandler::RawSignalHandler,
-                                           { SIGFPE, SIGSEGV, SIGILL, SIGBUS, SIGPIPE, SIGABRT },
+                                           { SIGFPE, SIGSEGV, SIGILL, SIGBUS, SIGPIPE, SIGABRT, SIGQUIT, SIGSYS },
                                            [](int sig) {
         UnixSignalHandler::instance()->resetToDefault(sig);
         char buffer[256];
@@ -387,6 +387,7 @@ static void logCrashInfo(LogToDestination logTo, const char *why, int stackFrame
 #if defined(Q_OS_LINUX)
     long tid = syscall(SYS_gettid);
     bool isMainThread = (tid == pid);
+
 #else
     long tid = -1;
     bool isMainThread = pthread_main_np();
@@ -540,7 +541,8 @@ static void crashHandler(const char *why, int stackFramesToIgnore)
     //  1) avoid recursions
     //  2) SIGABRT to re-enable standard abort() handling
     //  3) SIGINT, so that you can Ctrl+C the app if the crash handler ends up freezing
-    UnixSignalHandler::instance()->resetToDefault({ SIGFPE, SIGSEGV, SIGILL, SIGBUS, SIGPIPE, SIGABRT, SIGINT });
+    UnixSignalHandler::instance()->resetToDefault({ SIGFPE, SIGSEGV, SIGILL, SIGBUS,
+                                                    SIGPIPE, SIGABRT, SIGINT, SIGQUIT, SIGSYS });
 
     logCrashInfo(Console, why, stackFramesToIgnore);
 
@@ -573,11 +575,12 @@ static void crashHandler(const char *why, int stackFramesToIgnore)
         logCrashInfo(Dlt, why, stackFramesToIgnore);
 #  endif
 
-    // make sure to kill our sub-process as well
-    kill(0, SIGABRT);
+    // make sure to terminate our sub-process as well, but not ourselves
+    signal(SIGTERM, SIG_IGN);
+    kill(0, SIGTERM);
 
     if (dumpCore) {
-        logMsg(Console, "\n > the process will be aborted (core dumped)\n\n");
+        logMsg(Console, "\n > the process will be aborted (core dumped)\n");
         abort();
     }
 
diff --git a/src/common-lib/unixsignalhandler.cpp b/src/common-lib/unixsignalhandler.cpp
index cd51fae3..c208412b 100644
--- a/src/common-lib/unixsignalhandler.cpp
+++ b/src/common-lib/unixsignalhandler.cpp
@@ -56,15 +56,6 @@
 
 QT_BEGIN_NAMESPACE_AM
 
-#if defined(Q_OS_UNIX)
-
-// make it clear in the valgrind backtrace that this is a deliberate leak
-static void *malloc_valgrind_ignore(size_t size)
-{
-    return malloc(size);
-}
-#endif
-
 // sigmask() is not available on Windows
 UnixSignalHandler::am_sigmask_t UnixSignalHandler::am_sigmask(int sig)
 {
@@ -73,12 +64,29 @@ UnixSignalHandler::am_sigmask_t UnixSignalHandler::am_sigmask(int sig)
 
 UnixSignalHandler *UnixSignalHandler::s_instance = nullptr;
 
+#if defined(Q_OS_UNIX)
+// make it clear in the valgrind backtrace that this is a deliberate leak
+static void *malloc_valgrind_ignore(size_t size)
+{
+    return malloc(size);
+}
+
 UnixSignalHandler::UnixSignalHandler()
     : QObject()
-#if defined(Q_OS_UNIX)
     , m_pipe { -1, -1 }
-#endif
+{
+    // Setup alternate signal stack (to get backtrace for stack overflow)
+    stack_t sigstack;
+    // valgrind will report this as leaked: nothing we can do about it
+    sigstack.ss_sp = malloc_valgrind_ignore(SIGSTKSZ);
+    sigstack.ss_size = SIGSTKSZ;
+    sigstack.ss_flags = 0;
+    sigaltstack(&sigstack, nullptr);
+}
+#else
+UnixSignalHandler::UnixSignalHandler() : QObject()
 { }
+#endif
 
 UnixSignalHandler *UnixSignalHandler::instance()
 {
@@ -208,13 +216,6 @@ bool UnixSignalHandler::install(Type handlerType, const std::initializer_list<in
         m_handlers.emplace_back(sig, handlerType == ForwardedToEventLoopHandler, handler);
 
 #if defined(Q_OS_UNIX)
-    // Use alternate signal stack to get backtrace for stack overflow
-    stack_t sigstack;
-    sigstack.ss_sp = malloc_valgrind_ignore(SIGSTKSZ); // valgrind will report this as leaked: nothing we can do about it
-    sigstack.ss_size = SIGSTKSZ;
-    sigstack.ss_flags = 0;
-    sigaltstack(&sigstack, nullptr);
-
     struct sigaction sigact;
     sigact.sa_flags = SA_ONSTACK;
     sigact.sa_handler = sigHandler;