GDB not reacting Ctrl-C when after fork() and setsid() - gdb

Question

I'm debugging a daemon and after it forks and child calls setsid() the execution cannot be interrupted by pressing Ctrl-C.
Here is a simple example:
// test.c
#include <unistd.h>
#include <stdio.h>
int main()
{
int i = 0;
if(fork())
{
printf("Parent\n");
return 1;
}
printf("Child\n");
setsid();
for(;;)
i++;
return 0;
}
Steps to reproduce:
gcc -g -o test test.c
gdb ./test
In gdb shell:
set follow-fork-mode child (because by default gdb follows parent process)
run
press Ctrl-C
And nothing happens. Even if I send SIGINT to the process, it is hanging. I have to kill gdb to stop this.
But I can interrupt loop if I send SIGINT before pressing Ctrl-C. If I set breakpoint inside loop, process stops on it fine.
If I comment out one of "fork()" or "setsid()", everything works as expected.
Some workarounds I know are:
Run process in foreground for debugging purpose
Add some sleep in child process after it daemonizes. And attach gdb to it
But maybe someone knows better solution or can explain, why this is happening.
Thanks in advance
Linux 4.12.10-1 x86_64
gcc 7.1.1
GNU gdb (GDB) 8.0
UPD 2017-09-11:
Some more research (here stat <process> stands for grep State /proc/<pid of process>/status)
Scenario 1 (send SIGINT before pressing Ctrl-C, in this case everything work as expected)
$ stat gdb
State: S (sleeping)
$ stat test
State: R (running)
$ killall -SIGINT test
$ stat gdb
State: S (sleeping)
$ stat test
State: t (tracing stop)
Scenario 2 (send SIGINT after pressing Ctrl-C, in this case gdb seems to be hanging)
$ stat gdb
State: R (running)
$ stat test
State: R (running)
$ killall -SIGINT test
$ stat gdb
State: R (running)
$ stat test
State: t (tracing stop)
$ grep TracerPid /proc/`pidof test`/status
TracerPid: 26533
Backtrace of gdb:
#0 0x00007fbf7bb316c0 in __write_nocancel () from /usr/lib/libpthread.so.0
#1 0x00005625e2cc090c in serial_event_set(serial_event*) ()
#2 <signal handler called>
#3 0x00007fbf7aae3ba7 in kill () from /usr/lib/libc.so.6
#4 0x00005625e2cf908b in default_target_pass_ctrlc(target_ops*) ()
#5 0x00005625e2d0b3a4 in maybe_quit() ()
#6 0x00005625e2c24e92 in invoke_async_signal_handlers() ()
#7 0x00005625e2c259e6 in start_event_loop() ()
#8 0x00005625e2c7d33b in captured_command_loop(void*) ()
#9 0x00005625e2c27c55 in catch_errors(int (*)(void*), void*, char const*, return_mask) ()
#10 0x00005625e2c7e63f in gdb_main(captured_main_args*) ()
#11 0x00005625e2a62bec in main ()