core: unblock fatal (crashing) signals in all threads

Currently all non-main threads have all the signals blocked, however
according to `man pthread_sigmask':

> If SIGBUS, SIGFPE, SIGILL, or SIGSEGV are generated while they
> are blocked, the result is undefined, unless the signal was
> generated by kill(2), sigqueue(3), or raise(3).

On macOS they are actually blocked, causing the faulting instruction
to loop indefinitely. While on Linux they are not blocked, however the
signal handler registered by sigaction is not executed. Don't block them.

Closes #8023
Closes #8083

NO_DOC=bugfix

changelogs/unreleased/gh-8083-fatal-signal-handler.md

+## bugfix/core
+
+* Fixed Tarantool being stuck during a crash on macOS (gh-8023).
+
+* Fixed a bug that prevents crash report being collected (gh-8083).

src/lib/core/errinj.h

@@ -119,6 +119,7 @@ struct errinj {
 	_(ERRINJ_REPLICASET_VCLOCK, ERRINJ_BOOL, {.bparam = false}) \
 	_(ERRINJ_REPLICA_JOIN_DELAY, ERRINJ_BOOL, {.bparam = false}) \
 	_(ERRINJ_SIGILL_MAIN_THREAD, ERRINJ_BOOL, {.bparam = false}) \
+	_(ERRINJ_SIGILL_NONMAIN_THREAD, ERRINJ_BOOL, {.bparam = false}) \
 	_(ERRINJ_SIO_READ_MAX, ERRINJ_INT, {.iparam = -1}) \
 	_(ERRINJ_SNAP_COMMIT_DELAY, ERRINJ_BOOL, {.bparam = false}) \
 	_(ERRINJ_SNAP_COMMIT_FAIL, ERRINJ_BOOL, {.bparam = false}) \

src/lib/core/fiber.c

@@ -1732,6 +1732,7 @@ void *cord_thread_func(void *p)
 	ct_arg->is_started = true;
 	tt_pthread_cond_signal(&ct_arg->start_cond);
 	tt_pthread_mutex_unlock(&ct_arg->start_mutex);
+	ERROR_INJECT_SIGILL(ERRINJ_SIGILL_NONMAIN_THREAD);
 	void *res = f(arg);
 	/*
 	 * cord()->on_exit initially holds NULL. This field is

src/tt_pthread.h

@@ -264,12 +264,18 @@
 	tt_pthread_error(e__);			\
 })
 
-/** Make sure the created thread blocks all signals,
- * they are handled in the main thread.
+/**
+ * Make sure the created thread blocks all signals, they are handled in the main
+ * thread. Except SIGILL, SIGBUS, SIGFPE and SIGSEGV, that cannot be blocked and
+ * are handled by the thread that triggered them (see crash_signal_init).
  */
 #define tt_pthread_create(thread, attr, run, arg)	\
 ({	sigset_t set, oldset;				\
 	sigfillset(&set);				\
+	sigdelset(&set, SIGILL);			\
+	sigdelset(&set, SIGBUS);			\
+	sigdelset(&set, SIGFPE);			\
+	sigdelset(&set, SIGSEGV);			\
 	pthread_sigmask(SIG_BLOCK, &set, &oldset);	\
 	int e__ = pthread_create(thread, attr, run, arg);\
 	pthread_sigmask(SIG_SETMASK, &oldset, NULL);	\

test/app-luatest/gh_8083_fatal_signal_handler_test.lua

 local t = require('luatest')
-local g = t.group('gh-8083', {{errinj = 'ERRINJ_SIGILL_MAIN_THREAD'}})
+local g = t.group('gh-8083', {{errinj = 'ERRINJ_SIGILL_MAIN_THREAD'},
+                              {errinj = 'ERRINJ_SIGILL_NONMAIN_THREAD'}})
 
 g.before_each(function(cg)
     local server = require('luatest.server')

test/box/errinj.result

@@ -94,6 +94,7 @@ evals
   - ERRINJ_REPLICASET_VCLOCK: false
   - ERRINJ_REPLICA_JOIN_DELAY: false
   - ERRINJ_SIGILL_MAIN_THREAD: false
+  - ERRINJ_SIGILL_NONMAIN_THREAD: false
   - ERRINJ_SIO_READ_MAX: -1
   - ERRINJ_SNAP_COMMIT_DELAY: false
   - ERRINJ_SNAP_COMMIT_FAIL: false