signal_handler: fallback to strsignal when sys_siglist is not impleme…

…nted

musl libc does not provide sys_siglist.

Added feature check for sys_siglist and a fallback to strsignal().

Assumes strsignal(3) is not thread safe (http://pubs.opengroup.org/onlinepubs/9699919799/functions/strsignal.html). Added WITH_THREAD_SAFE_STRSIGNAL build option for thread safe impls.

Signed-off-by: John Coyle <dx9err@gmail.com>

CMakeLists.txt

@@ -82,8 +82,8 @@ include(CheckSymbolExists)
 CHECK_SYMBOL_EXISTS(__u8 "sys/types.h;linux/types.h" HAVE___U8)
 CHECK_SYMBOL_EXISTS(__u64 "sys/types.h;linux/types.h" HAVE___U64)
 CHECK_SYMBOL_EXISTS(__s64 "sys/types.h;linux/types.h" HAVE___S64)
-
 CHECK_SYMBOL_EXISTS(res_nquery "resolv.h" HAVE_RES_NQUERY)
+CHECK_SYMBOL_EXISTS(sys_siglist "signal.h;string.h" HAVE_SYS_SIGLIST)
 
 include(CheckCXXSourceCompiles)
 CHECK_CXX_SOURCE_COMPILES("
@@ -223,6 +223,11 @@ if(WITH_THREAD_SAFE_RES_QUERY)
     set(HAVE_THREAD_SAFE_RES_QUERY 1 CACHE INTERNAL "Thread safe res_query supported.")
 endif(WITH_THREAD_SAFE_RES_QUERY)
 
+option(WITH_THREAD_SAFE_STRSIGNAL "strsignal is thread safe" OFF)
+if(WITH_THREAD_SAFE_STRSIGNAL)
+    set(HAVE_THREAD_SAFE_STRSIGNAL 1 CACHE INTERNAL "Thread safe strsignal supported.")
+endif(WITH_THREAD_SAFE_STRSIGNAL)
+
 # Now create a useable config.h
 configure_file(
   ${PROJECT_SOURCE_DIR}/src/include/config-h.in.cmake

configure.ac

@@ -1090,6 +1090,9 @@ AC_CHECK_FUNC([pthread_spin_init],
 LIBS="$saved_LIBS"
 CFLAGS="$saved_CFLAGS"
 
+
+AC_CHECK_DECL([sys_siglist],[AC_DEFINE(HAVE_SYS_SIGLIST, 1, [Define if you have sys_siglist])],[], [#include <signal.h> #include <string.h>])
+
 AC_CHECK_TYPES([int8_t, uint8_t, int16_t, uint16_t, int32_t, uint32_t,
   int64_t, uint64_t])
 

src/global/signal_handler.cc

@@ -12,6 +12,7 @@
  *
  */
 
+#include "acconfig.h"
 #include "common/BackTrace.h"
 #include "common/perf_counters.h"
 #include "common/config.h"
@@ -30,6 +31,9 @@
 extern char *sys_siglist[]; 
 #endif 
 
+#ifndef HAVE_THREAD_SAFE_STRSIGNAL
+static Mutex lock("strsignal");
+#endif
 
 void install_sighandler(int signum, signal_handler_t handler, int flags)
 {
@@ -54,7 +58,7 @@ void install_sighandler(int signum, signal_handler_t handler, int flags)
 #else
     snprintf(buf, sizeof(buf), "install_sighandler: sigaction returned "
 	    "%d when trying to install a signal handler for %s\n",
-	     ret, sys_siglist[signum]);
+	     ret, sig_str(signum));
 #endif
     dout_emergency(buf);
     exit(1);
@@ -99,8 +103,9 @@ static void handle_fatal_signal(int signum)
 	    "in thread %llx\n", message, (unsigned long long)pthread_self());
 #else
   snprintf(buf, sizeof(buf), "*** Caught signal (%s) **\n "
-	    "in thread %llx\n", sys_siglist[signum], (unsigned long long)pthread_self());
+	    "in thread %llx\n", sig_str(signum), (unsigned long long)pthread_self());
 #endif
+
   dout_emergency(buf);
   pidfile_remove();
 
@@ -376,5 +381,14 @@ void unregister_async_signal_handler(int signum, signal_handler_t handler)
   g_signal_handler->unregister_handler(signum, handler);
 }
 
-
-
+char* sig_str(int signum)
+{
+#ifdef HAVE_SYS_SIGLIST
+  return sys_siglist[signum];
+#else
+# ifndef HAVE_THREAD_SAFE_STRSIGNAL
+  Mutex::Locker l(lock);
+# endif
+  return strsignal(signum);
+#endif
+}

src/global/signal_handler.h

@@ -20,6 +20,8 @@
 
 typedef void (*signal_handler_t)(int);
 
+char* sig_str(int signum);
+
 void install_sighandler(int signum, signal_handler_t handler, int flags);
 
 // handles SIGHUP

src/include/config-h.in.cmake

@@ -246,4 +246,10 @@
 /* res_query is thread safe */
 #cmakedefine HAVE_THREAD_SAFE_RES_QUERY
 
+/* Define if HAVE_SYS_SIGLIST */
+#cmakedefine HAVE_SYS_SIGLIST
+
+/* Define if HAVE_THREAD_SAFE_STRSIGNAL */
+#cmakedefine HAVE_THREAD_SAFE_STRSIGNAL
+
 #endif /* CONFIG_H */

src/mds/MDSDaemon.cc

@@ -993,7 +993,7 @@ void MDSDaemon::_handle_mds_map(MDSMap *oldmap)
 void MDSDaemon::handle_signal(int signum)
 {
   assert(signum == SIGINT || signum == SIGTERM);
-  derr << "*** got signal " << sys_siglist[signum] << " ***" << dendl;
+  derr << "*** got signal " << sig_str(signum) << " ***" << dendl;
   {
     Mutex::Locker l(mds_lock);
     if (stopping) {

src/mon/Monitor.cc

@@ -62,6 +62,8 @@
 #include "common/perf_counters.h"
 #include "common/admin_socket.h"
 
+#include "global/signal_handler.h"
+
 #include "include/color.h"
 #include "include/ceph_fs.h"
 #include "include/str_list.h"
@@ -356,7 +358,7 @@ void Monitor::do_admin_command(string command, cmdmap_t& cmdmap, string format,
 void Monitor::handle_signal(int signum)
 {
   assert(signum == SIGINT || signum == SIGTERM);
-  derr << "*** Got Signal " << sys_siglist[signum] << " ***" << dendl;
+  derr << "*** Got Signal " << sig_str(signum) << " ***" << dendl;
   shutdown();
 }
 

src/osd/OSD.cc

@@ -1648,7 +1648,7 @@ void cls_initialize(ClassHandler *ch);
 void OSD::handle_signal(int signum)
 {
   assert(signum == SIGINT || signum == SIGTERM);
-  derr << "*** Got signal " << sys_siglist[signum] << " ***" << dendl;
+  derr << "*** Got signal " << sig_str(signum) << " ***" << dendl;
   shutdown();
 }
 

src/test/mon/test_mon_workloadgen.cc

@@ -935,7 +935,7 @@ void handle_test_signal(int signum)
   if ((signum != SIGINT) && (signum != SIGTERM))
     return;
 
-  std::cerr << "*** Got signal " << sys_siglist[signum] << " ***" << std::endl;
+  std::cerr << "*** Got signal " << sig_str(signum) << " ***" << std::endl;
   Mutex::Locker l(shutdown_lock);
   if (shutdown_timer) {
     shutdown_timer->cancel_all_events();