From: Oleg Nesterov Introduce the new PF_KTHREAD flag to mark the kernel threads. It is set by INIT_TASK() and copied to the forked childs (we could set it in kthreadd() along with PF_NOFREEZE instead). daemonize() was changed as well. In that case testing of PF_KTHREAD is racy, but daemonize() is hopeless anyway. This flag is cleared in do_execve(), before search_binary_handler(). Probably not the best place, we can do this in exec_mmap() or in start_thread(), or clear it along with PF_FORKNOEXEC. But I think this doesn't matter in practice, and if do_execve() fails kthread should die soon. Signed-off-by: Oleg Nesterov Cc: Roland McGrath Signed-off-by: Andrew Morton --- fs/exec.c | 1 + include/linux/init_task.h | 2 +- include/linux/sched.h | 1 + kernel/exit.c | 2 +- 4 files changed, 4 insertions(+), 2 deletions(-) diff -puN fs/exec.c~introduce-pf_kthread-flag fs/exec.c --- a/fs/exec.c~introduce-pf_kthread-flag +++ a/fs/exec.c @@ -1324,6 +1324,7 @@ int do_execve(char * filename, if (retval < 0) goto out; + current->flags &= ~PF_KTHREAD; retval = search_binary_handler(bprm,regs); if (retval >= 0) { /* execve success */ diff -puN include/linux/init_task.h~introduce-pf_kthread-flag include/linux/init_task.h --- a/include/linux/init_task.h~introduce-pf_kthread-flag +++ a/include/linux/init_task.h @@ -122,7 +122,7 @@ extern struct group_info init_groups; .state = 0, \ .stack = &init_thread_info, \ .usage = ATOMIC_INIT(2), \ - .flags = 0, \ + .flags = PF_KTHREAD, \ .lock_depth = -1, \ .prio = MAX_PRIO-20, \ .static_prio = MAX_PRIO-20, \ diff -puN include/linux/sched.h~introduce-pf_kthread-flag include/linux/sched.h --- a/include/linux/sched.h~introduce-pf_kthread-flag +++ a/include/linux/sched.h @@ -1507,6 +1507,7 @@ static inline void put_task_struct(struc #define PF_MEMPOLICY 0x10000000 /* Non-default NUMA mempolicy */ #define PF_MUTEX_TESTER 0x20000000 /* Thread belongs to the rt mutex tester */ #define PF_FREEZER_SKIP 0x40000000 /* Freezer should not count it as freezeable */ +#define PF_KTHREAD 0x80000000 /* I am a kernel thread */ /* * Only the _current_ task can read/write to tsk->flags, but other diff -puN kernel/exit.c~introduce-pf_kthread-flag kernel/exit.c --- a/kernel/exit.c~introduce-pf_kthread-flag +++ a/kernel/exit.c @@ -421,7 +421,7 @@ void daemonize(const char *name, ...) * We don't want to have TIF_FREEZE set if the system-wide hibernation * or suspend transition begins right now. */ - current->flags |= PF_NOFREEZE; + current->flags |= (PF_NOFREEZE | PF_KTHREAD); if (current->nsproxy != &init_nsproxy) { get_nsproxy(&init_nsproxy); _