In very few conditions it is possible that procfs subsystem may race with exit routine.

Panic string : kernel memory fault

>  0 boot                 src/kernel/arch/alpha/machdep.c : 2725
   1 panic                src/kernel/bsd/subr_prf.c : 1616
   2 trap                 src/kernel/arch/alpha/trap.c : 2289
   3 _XentMM              src/kernel/arch/alpha/locore.s : 2242
   4 simple_lock          src/kernel/arch/alpha/lockprim.s : 744
   5 task_deallocate      src/kernel/kern/task.c : 869
   6 procfs_lookup        src/kernel/procfs/procfs_vnops.c : 1198
   7 namei                src/kernel/vfs/vfs_lookup.c : 1081
   8 vn_open              src/kernel/vfs/vfs_vnops.c : 802
   9 copen                src/kernel/vfs/vfs_syscalls.c : 3660
  10 syscall              src/kernel/arch/alpha/syscall_trap.c : 725
  11 _Xsyscall            src/kernel/arch/alpha/locore.s : 1885

