[9fans] syscall silently kill processes

[andrey100100100@gmail.com]

Hi all!

Strange behavior of syscall 'read' with signal 'alarm' in followed
simple program (ip/port - not matter):

-----------------------------------------------------------------------
#include <u.h>
#include <libc.h>
#include <thread.h>

static int
handler_alarm(void *, char *msg)
{
        if(strstr(msg, "alarm"))
                return 1;

        return 0;
}

static void
proc_udp(void *)
{
        char resp[512];
        char req[] = "request";
        int fd;

        threadnotify(handler_alarm, 1);

        if((fd = dial("udp!185.157.221.201!5678", nil, nil, nil)) >=
0){
                if(write(fd, req, strlen(req)) == strlen(req)){
                        fprint(1, "start\n");
                        alarm(2000);
                        read(fd, resp, sizeof(resp));
                        alarm(0);
                        fprint(1, "end\n");
                }
                close(fd);
        }

        threadexits(nil);
}

int mainstacksize = 5242880;

void
threadmain(int argc, char *argv[])
{
        for(int i = 0; i < 80; i++){
                proccreate(proc_udp, nil, 10240);
        }

        sleep(5000);
        threadexitsall(nil);
}
-----------------------------------------------------------------------


cpu% 6.out | grep end | wc -l
     33

sometimes little more or less
but

cpu% 6.out | grep start | wc -l
     80
     
always.

Testing on Miller's RPi and 9front (amd64 & RPi 2)


Why does read() kill process?
Why not always?
Why number of 'ended' processes arond 33?
This is normal behavior?
How to fix the program so that the processes do not lost?


Can someone point me in the right direction?


Thanks!
Andrey

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