glustershd crashed since the fresh_children were -1. 

Setup:

On the setup of bugs 3637, 3639 (2 replica volume with 1 fuse and 1 nfs client).
ran the tests.

On fuse client kernel untar in a while loop
On nfs client rm -rf of the untarred kernel

Killed one of the bricks, slept and brought the brick up. On other machine volume set was running in a loop.

This is the backtrace of the core.

Core was generated by `/usr/local/sbin/glusterfs -s localhost --volfile-id gluster/glustershd -p /etc/'.
Program terminated with signal 6, Aborted.
#0  0x00000030b8e30265 in raise () from /lib64/libc.so.6
(gdb) bt
#0  0x00000030b8e30265 in raise () from /lib64/libc.so.6
#1  0x00000030b8e31d10 in abort () from /lib64/libc.so.6
#2  0x00000030b8e296e6 in __assert_fail () from /lib64/libc.so.6
#3  0x00002aaaacf2ba12 in afr_inode_set_read_ctx (this=0x15659800, inode=0x2aaab29e3b38, read_child=1, fresh_children=0x1570a380)
    at ../../../../../xlators/cluster/afr/src/afr-common.c:419
#4  0x00002aaaacf06dbd in afr_sh_inode_set_read_ctx (sh=0x156fb7e8, this=0x15659800)
    at ../../../../../xlators/cluster/afr/src/afr-self-heal-data.c:642
#5  0x00002aaaacf070e4 in afr_sh_data_fix (frame=0x2b771b93cad8, this=0x15659800)
    at ../../../../../xlators/cluster/afr/src/afr-self-heal-data.c:705
#6  0x00002aaaacf079b0 in afr_sh_data_fstat_cbk (frame=0x2b771b93cad8, cookie=0x1, this=0x15659800, op_ret=-1, op_errno=107, 
    buf=0x7fff6d689d70) at ../../../../../xlators/cluster/afr/src/afr-self-heal-data.c:885
#7  0x00002aaaaccb5248 in client3_1_fstat_cbk (req=0x2aaaad36c534, iov=0x7fff6d689ee0, count=1, myframe=0x2b771b6b2790)
    at ../../../../../xlators/protocol/client/src/client3_1-fops.c:1198
#8  0x00002b771a9f6410 in saved_frames_unwind (saved_frames=0x15666290) at ../../../../rpc/rpc-lib/src/rpc-clnt.c:385
#9  0x00002b771a9f652f in saved_frames_destroy (frames=0x15666290) at ../../../../rpc/rpc-lib/src/rpc-clnt.c:403
#10 0x00002b771a9f6a03 in rpc_clnt_connection_cleanup (conn=0x1565fa60) at ../../../../rpc/rpc-lib/src/rpc-clnt.c:559
#11 0x00002b771a9f7455 in rpc_clnt_notify (trans=0x1565fd60, mydata=0x1565fa60, event=RPC_TRANSPORT_DISCONNECT, data=0x1565fd60)
    at ../../../../rpc/rpc-lib/src/rpc-clnt.c:863
#12 0x00002b771a9f39f3 in rpc_transport_notify (this=0x1565fd60, event=RPC_TRANSPORT_DISCONNECT, data=0x1565fd60)
    at ../../../../rpc/rpc-lib/src/rpc-transport.c:498
#13 0x00002aaaaab59006 in socket_event_poll_err (this=0x1565fd60) at ../../../../../rpc/rpc-transport/socket/src/socket.c:694
#14 0x00002aaaaab5d47c in socket_event_handler (fd=27, idx=20, data=0x1565fd60, poll_in=1, poll_out=0, poll_err=24)
    at ../../../../../rpc/rpc-transport/socket/src/socket.c:1797
#15 0x00002b771a79f84c in event_dispatch_epoll_handler (event_pool=0x1564c960, events=0x156513f0, i=0)
    at ../../../libglusterfs/src/event.c:794
#16 0x00002b771a79fa51 in event_dispatch_epoll (event_pool=0x1564c960) at ../../../libglusterfs/src/event.c:856
#17 0x00002b771a79fdab in event_dispatch (event_pool=0x1564c960) at ../../../libglusterfs/src/event.c:956
#18 0x000000000040784d in main (argc=11, argv=0x7fff6d68a518) at ../../../glusterfsd/src/glusterfsd.c:1592
(gdb) f 3
#3  0x00002aaaacf2ba12 in afr_inode_set_read_ctx (this=0x15659800, inode=0x2aaab29e3b38, read_child=1, fresh_children=0x1570a380)
    at ../../../../../xlators/cluster/afr/src/afr-common.c:419
419             GF_ASSERT (afr_is_child_present (fresh_children, priv->child_count,
(gdb) l
414             afr_private_t      *priv  = NULL;
415
416             priv = this->private;
417             GF_ASSERT (read_child >= 0);
418             GF_ASSERT (fresh_children);
419             GF_ASSERT (afr_is_child_present (fresh_children, priv->child_count,
420                                              read_child));
421
422             params.op = AFR_INODE_SET_READ_CTX;
423             params.u.read_ctx.read_child     = read_child;
(gdb) l afr_is_child_present
455     }
456
457     gf_boolean_t
458     afr_is_child_present (int32_t *success_children, int32_t child_count,
459                           int32_t child)
460     {
461             gf_boolean_t             success_child = _gf_false;
462             int                      i = 0;
463
464             GF_ASSERT (child < child_count);
(gdb) 
465
466             for (i = 0; i < child_count; i++) {
467                     if (success_children[i] == -1)
468                             break;
469                     if (child == success_children[i]) {
470                             success_child = _gf_true;
471                             break;
472                     }
473             }
474             return success_child;
(gdb) p fresh_children
$1 = (int32_t *) 0x1570a380
(gdb) p fresh_children[0]
$2 = -1
(gdb) p fresh_children[1]
$3 = -1
(gdb)  p read_child
$4 = 1
(gdb)