[perl #129228] [SEGV] concurrent network access segfaults in libmoar.so

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# New Ticket Created by  Robert Lemmen 
# Please include the string:  [perl #129228]
# in the subject line of all future correspondence about this issue. 
# <URL: https://rt.perl.org/Ticket/Display.html?id=129228 >


this simple program:

-----------------------8<-------------------------------

use v6;

use HTTP::Client;

my $n = 4;

my @promises;
for 1..$n {
    push @promises, start {
        my $i = 0;
        # when increasing n above, the total runtime changes as expected
#        for 1..(5/$n) {
#            say $*THREAD.id;
#            sleep 1;
#        }
        # funkyly, it increases dramatically from n=1 to n=2 , and then
        # stays there for n=3 and n=4
        my $client = HTTP::Client.new;
        for 1..100 {
            say sprintf("%2i %2i", $*THREAD.id,  $i++) ~ ' ' ~ now;
            for 1..(100/$n) {
               my $response = $client.get('http://localhost:80/');
           }
        }
    }
}
await Promise.allof(@promises)
----------------------->8-------------------------------

segfaults for me every now and then if n>=2. core dumps show:

Program terminated with signal SIGABRT, Aborted.
#0  0x00007fa0e1435067 in __GI_raise (sig=sig@entry=6) at 
../nptl/sysdeps/unix/sysv/linux/raise.c:56
56      ../nptl/sysdeps/unix/sysv/linux/raise.c: No such file or directory.
(gdb) bt
#0  0x00007fa0e1435067 in __GI_raise (sig=sig@entry=6) at 
../nptl/sysdeps/unix/sysv/linux/raise.c:56
#1  0x00007fa0e1436448 in __GI_abort () at abort.c:89
#2  0x00007fa0e14731b4 in __libc_message (do_abort=do_abort@entry=1, 
fmt=fmt@entry=0x7fa0e1568530 "*** Error in `%s': %s: 0x%s ***\n")
    at ../sysdeps/posix/libc_fatal.c:175
#3  0x00007fa0e147898e in malloc_printerr (action=1, str=0x7fa0e1568718 "double 
free or corruption (fasttop)", ptr=<optimized out>)
    at malloc.c:4996
#4  0x00007fa0e1479696 in _int_free (av=<optimized out>, p=<optimized out>, 
have_lock=0) at malloc.c:3840
#5  0x00007fa0e190eb42 in MVM_interp_run (tc=0x5e09, tc@entry=0x43b72e0, 
initial_invoke=0x0, invoke_data=0x6, invoke_data@entry=0x43dfde0)
    at src/core/interp.c:1601
#6  0x00007fa0e19238de in start_thread (data=0x43dfde0) at src/core/threads.c:77
#7  0x00007fa0e19ea267 in uv.thread_start () from 
//home/rlemmen/perl6env/rakudobrew/moar-nom/nqp/MoarVM/../../install/lib/libmoar.so
#8  0x00007fa0e0eea0a4 in start_thread (arg=0x7fa0ddd36700) at 
pthread_create.c:309
#9  0x00007fa0e14e887d in clone () at 
../sysdeps/unix/sysv/linux/x86_64/clone.S:111

(perhaps)interestingly this program also hangs for a second or so every now and 
then

please let me know how I can help debug this!

regards  robert