introduce PF_KTHREAD flag

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 <oleg@tv-sign.ru>
Cc: Roland McGrath <roland@redhat.com>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>

1 files changed, 1 insertions, 1 deletions

diff --git a/kernel/exit.c b/kernel/exit.c
index a7799d8a6404..28a44a2612dc 100644
--- a/kernel/exit.c
+++ b/kernel/exit.c
@@ -430,7 +430,7 @@ 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);