typically I run "emacs -nw" within xterm, and often I stop them with CTRL-Z and keep them in background.

now I've seen 2+ times that emacs loops and hogs both memory and cpu after shutting down X11 going to runlevel 3.  likely this was a leftover emacs from background.

from top:

  PID USER      PR  NI  VIRT  RES  SHR S %CPU %MEM    TIME+  COMMAND                                                                                        
23902 harald    20   0 7222m 3.4g  608 R  100 88.9  59:28.72 emacs-gtk                                                                                       

from strace:

ioctl(3, SNDCTL_TMR_TIMEBASE or TCGETS, 0x7fff1f32e320) = -1 EIO (Input/output error)
ioctl(3, SNDCTL_TMR_STOP or TCSETSW, {B0 -opost -isig -icanon -echo ...}) = -1 EIO (Input/output error)
write(3, "\7", 1)                       = -1 EIO (Input/output error)
brk(0x1bb35e000)                        = 0x1bb339000
mmap(NULL, 1048576, PROT_READ|PROT_WRITE, MAP_PRIVATE|MAP_ANONYMOUS, -1, 0) = -1 ENOMEM (Cannot allocate memory)
brk(0x1bb35e000)                        = 0x1bb339000
mmap(NULL, 1048576, PROT_READ|PROT_WRITE, MAP_PRIVATE|MAP_ANONYMOUS, -1, 0) = -1 ENOMEM (Cannot allocate memory)
brk(0x1bb35a000)                        = 0x1bb339000
mmap(NULL, 1048576, PROT_READ|PROT_WRITE, MAP_PRIVATE|MAP_ANONYMOUS, -1, 0) = -1 ENOMEM (Cannot allocate memory)
mmap(NULL, 134217728, PROT_NONE, MAP_PRIVATE|MAP_ANONYMOUS|MAP_NORESERVE, -1, 0) = -1 ENOMEM (Cannot allocate memory)
mmap(NULL, 67108864, PROT_NONE, MAP_PRIVATE|MAP_ANONYMOUS|MAP_NORESERVE, -1, 0) = -1 ENOMEM (Cannot allocate memory)
mmap(NULL, 134217728, PROT_NONE, MAP_PRIVATE|MAP_ANONYMOUS|MAP_NORESERVE, -1, 0) = -1 ENOMEM (Cannot allocate memory)
mmap(NULL, 67108864, PROT_NONE, MAP_PRIVATE|MAP_ANONYMOUS|MAP_NORESERVE, -1, 0) = -1 ENOMEM (Cannot allocate memory)
ioctl(3, SNDCTL_TMR_TIMEBASE or TCGETS, 0x7fff1f32e320) = -1 EIO (Input/output error)
ioctl(3, SNDCTL_TMR_STOP or TCSETSW, {B0 -opost -isig -icanon -echo ...}) = -1 EIO (Input/output error)
write(3, "\7", 1)                       = -1 EIO (Input/output error)
brk(0x1bb35e000)                        = 0x1bb339000
mmap(NULL, 1048576, PROT_READ|PROT_WRITE, MAP_PRIVATE|MAP_ANONYMOUS, -1, 0) = -1 ENOMEM (Cannot allocate memory)
brk(0x1bb35e000)                        = 0x1bb339000
mmap(NULL, 1048576, PROT_READ|PROT_WRITE, MAP_PRIVATE|MAP_ANONYMOUS, -1, 0) = -1 ENOMEM (Cannot allocate memory)
rt_sigprocmask(SIG_BLOCK, [IO], [HUP TERM IO], 8) = 0
ioctl(3, FIONREAD, [0])                 = -1 EIO (Input/output error)
kill(23902, SIGHUP)                     = 0
brk(0x1bb35a000)                        = 0x1bb339000
mmap(NULL, 1048576, PROT_READ|PROT_WRITE, MAP_PRIVATE|MAP_ANONYMOUS, -1, 0) = -1 ENOMEM (Cannot allocate memory)
mmap(NULL, 134217728, PROT_NONE, MAP_PRIVATE|MAP_ANONYMOUS|MAP_NORESERVE, -1, 0) = -1 ENOMEM (Cannot allocate memory)
mmap(NULL, 67108864, PROT_NONE, MAP_PRIVATE|MAP_ANONYMOUS|MAP_NORESERVE, -1, 0) = -1 ENOMEM (Cannot allocate memory)
mmap(NULL, 134217728, PROT_NONE, MAP_PRIVATE|MAP_ANONYMOUS|MAP_NORESERVE, -1, 0) = -1 ENOMEM (Cannot allocate memory)
mmap(NULL, 67108864, PROT_NONE, MAP_PRIVATE|MAP_ANONYMOUS|MAP_NORESERVE, -1, 0) = -1 ENOMEM (Cannot allocate memory)
ioctl(3, SNDCTL_TMR_TIMEBASE or TCGETS, 0x7fff1f32e320) = -1 EIO (Input/output error)
ioctl(3, SNDCTL_TMR_STOP or TCSETSW, {B0 -opost -isig -icanon -echo ...}) = -1 EIO (Input/output error)
write(3, "\7", 1)                       = -1 EIO (Input/output error)
brk(0x1bb35e000)                        = 0x1bb339000
mmap(NULL, 1048576, PROT_READ|PROT_WRITE, MAP_PRIVATE|MAP_ANONYMOUS, -1, 0) = -1 ENOMEM (Cannot allocate memory)
brk(0x1bb35e000)                        = 0x1bb339000
mmap(NULL, 1048576, PROT_READ|PROT_WRITE, MAP_PRIVATE|MAP_ANONYMOUS, -1, 0) = -1 ENOMEM (Cannot allocate memory)
brk(0x1bb35a000)                        = 0x1bb339000
mmap(NULL, 1048576, PROT_READ|PROT_WRITE, MAP_PRIVATE|MAP_ANONYMOUS, -1, 0) = -1 ENOMEM (Cannot allocate memory)
mmap(NULL, 134217728, PROT_NONE, MAP_PRIVATE|MAP_ANONYMOUS|MAP_NORESERVE, -1, 0) = -1 ENOMEM (Cannot allocate memory)
mmap(NULL, 67108864, PROT_NONE, MAP_PRIVATE|MAP_ANONYMOUS|MAP_NORESERVE, -1, 0) = -1 ENOMEM (Cannot allocate memory)
mmap(NULL, 134217728, PROT_NONE, MAP_PRIVATE|MAP_ANONYMOUS|MAP_NORESERVE, -1, 0) = -1 ENOMEM (Cannot allocate memory)
mmap(NULL, 67108864, PROT_NONE, MAP_PRIVATE|MAP_ANONYMOUS|MAP_NORESERVE, -1, 0) = -1 ENOMEM (Cannot allocate memory)
ioctl(3, SNDCTL_TMR_TIMEBASE or TCGETS, 0x7fff1f32e320) = -1 EIO (Input/output error)
ioctl(3, SNDCTL_TMR_STOP or TCSETSW, {B0 -opost -isig -icanon -echo ...}) = -1 EIO (Input/output error)
write(3, "\7", 1)                       = -1 EIO (Input/output error)
brk(0x1bb35e000)                        = 0x1bb339000