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Commit 7b34e428 authored Jul 25, 2008 by Oleg Nesterov Committed by Linus Torvalds Jul 25, 2008

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>

parent 3d749b9e

fs/exec.c

+1 −0

Original line number	Original line	Diff line number	Diff line
	@@ -1326,6 +1326,7 @@ int do_execve(char * filename,
	if (retval < 0)		if (retval < 0)
	goto out;		goto out;

			current->flags &= ~PF_KTHREAD;
	retval = search_binary_handler(bprm,regs);		retval = search_binary_handler(bprm,regs);
	if (retval >= 0) {		if (retval >= 0) {
	/* execve success */		/* execve success */

include/linux/init_task.h

+1 −1

Original line number	Original line	Diff line number	Diff line
	@@ -122,7 +122,7 @@ extern struct group_info init_groups;
	.state = 0, \		.state = 0, \
	.stack = &init_thread_info, \		.stack = &init_thread_info, \
	.usage = ATOMIC_INIT(2), \		.usage = ATOMIC_INIT(2), \
	.flags = 0, \		.flags = PF_KTHREAD, \
	.lock_depth = -1, \		.lock_depth = -1, \
	.prio = MAX_PRIO-20, \		.prio = MAX_PRIO-20, \
	.static_prio = MAX_PRIO-20, \		.static_prio = MAX_PRIO-20, \

include/linux/sched.h

+1 −0

Original line number	Original line	Diff line number	Diff line
	@@ -1483,6 +1483,7 @@ static inline void put_task_struct(struct task_struct *t)
	#define PF_EXITING 0x00000004 /* getting shut down */		#define PF_EXITING 0x00000004 /* getting shut down */
	#define PF_EXITPIDONE 0x00000008 /* pi exit done on shut down */		#define PF_EXITPIDONE 0x00000008 /* pi exit done on shut down */
	#define PF_VCPU 0x00000010 /* I'm a virtual CPU */		#define PF_VCPU 0x00000010 /* I'm a virtual CPU */
			#define PF_KTHREAD 0x00000020 /* I am a kernel thread */
	#define PF_FORKNOEXEC 0x00000040 /* forked but didn't exec */		#define PF_FORKNOEXEC 0x00000040 /* forked but didn't exec */
	#define PF_SUPERPRIV 0x00000100 /* used super-user privileges */		#define PF_SUPERPRIV 0x00000100 /* used super-user privileges */
	#define PF_DUMPCORE 0x00000200 /* dumped core */		#define PF_DUMPCORE 0x00000200 /* dumped core */

kernel/exit.c

+1 −1

Original line number	Original line	Diff line number	Diff line
	@@ -430,7 +430,7 @@ void daemonize(const char *name, ...)
	* We don't want to have TIF_FREEZE set if the system-wide hibernation		* We don't want to have TIF_FREEZE set if the system-wide hibernation
	* or suspend transition begins right now.		* or suspend transition begins right now.
	*/		*/
	current->flags \|= PF_NOFREEZE;		current->flags \|= (PF_NOFREEZE \| PF_KTHREAD);

	if (current->nsproxy != &init_nsproxy) {		if (current->nsproxy != &init_nsproxy) {
	get_nsproxy(&init_nsproxy);		get_nsproxy(&init_nsproxy);