procstat -kk

[silent@beastie][/a/cores]sudo sh -c 'i=0; while [ $i -lt 5 ]; do LC_ALL=C; date; procstat -kk `pgrep Xorg`; sleep 1; i=$((i+1)); done'
Sun Sep  4 20:12:42 EEST 2011
  PID    TID COMM             TDNAME           KSTACK
 1619 100424 Xorg             -                <running>
Sun Sep  4 20:12:43 EEST 2011
  PID    TID COMM             TDNAME           KSTACK
 1619 100424 Xorg             -                mi_switch+0x170 sleepq_catch_signals+0x27f sleepq_timedwait_sig+0x19 _cv_timedwait_sig+0x12b seltdwait+0x56 kern_select+0x64d select+0x5d syscallenter+0x19a syscall+0x4b Xfast_syscall+0xdd
Sun Sep  4 20:12:44 EEST 2011
  PID    TID COMM             TDNAME           KSTACK
 1619 100424 Xorg             -                mi_switch+0x170 sleepq_catch_signals+0x27f sleepq_timedwait_sig+0x19 _cv_timedwait_sig+0x12b seltdwait+0x56 kern_select+0x64d select+0x5d syscallenter+0x19a syscall+0x4b Xfast_syscall+0xdd
Sun Sep  4 20:12:45 EEST 2011
  PID    TID COMM             TDNAME           KSTACK
 1619 100424 Xorg             -                mi_switch+0x170 sleepq_catch_signals+0x27f sleepq_timedwait_sig+0x19 _cv_timedwait_sig+0x12b seltdwait+0x56 kern_select+0x64d select+0x5d syscallenter+0x19a syscall+0x4b Xfast_syscall+0xdd
Sun Sep  4 20:12:46 EEST 2011
  PID    TID COMM             TDNAME           KSTACK
 1619 100424 Xorg             -                mi_switch+0x170 sleepq_catch_signals+0x27f sleepq_timedwait_sig+0x19 _cv_timedwait_sig+0x12b seltdwait+0x56 kern_select+0x64d select+0x5d syscallenter+0x19a syscall+0x4b Xfast_syscall+0xdd