[PATCH] kill PF_DEAD flag

After the previous change (->flags & PF_DEAD) <=> (->state == EXIT_DEAD), we
don't need PF_DEAD any longer.
Signed-off-by: Oleg Nesterov <oleg@tv-sign.ru>
Cc: Ingo Molnar <mingo@elte.hu>
Signed-off-by: Andrew Morton <akpm@osdl.org>
Signed-off-by: Linus Torvalds <torvalds@osdl.org>

include/linux/sched.h

@@ -1061,7 +1061,6 @@ static inline void put_task_struct(struct task_struct *t)
 					/* Not implemented yet, only for 486*/
 #define PF_STARTING	0x00000002	/* being created */
 #define PF_EXITING	0x00000004	/* getting shut down */
-#define PF_DEAD		0x00000008	/* Dead */
 #define PF_FORKNOEXEC	0x00000040	/* forked but didn't exec */
 #define PF_SUPERPRIV	0x00000100	/* used super-user privileges */
 #define PF_DUMPCORE	0x00000200	/* dumped core */

kernel/exit.c

@@ -953,10 +953,8 @@ fastcall NORET_TYPE void do_exit(long code)
 	if (tsk->splice_pipe)
 		__free_pipe_info(tsk->splice_pipe);
 
-	/* PF_DEAD causes final put_task_struct after we schedule. */
 	preempt_disable();
-	BUG_ON(tsk->flags & PF_DEAD);
-	tsk->flags |= PF_DEAD;
+	/* causes final put_task_struct in finish_task_switch(). */
 	tsk->state = EXIT_DEAD;
 
 	schedule();

kernel/sched.c

@@ -1755,27 +1755,27 @@ static inline void finish_task_switch(struct rq *rq, struct task_struct *prev)
 	__releases(rq->lock)
 {
 	struct mm_struct *mm = rq->prev_mm;
-	unsigned long prev_task_flags;
+	long prev_state;
 
 	rq->prev_mm = NULL;
 
 	/*
 	 * A task struct has one reference for the use as "current".
-	 * If a task dies, then it sets EXIT_ZOMBIE in tsk->exit_state and
-	 * calls schedule one last time. The schedule call will never return,
-	 * and the scheduled task must drop that reference.
-	 * The test for EXIT_ZOMBIE must occur while the runqueue locks are
+	 * If a task dies, then it sets EXIT_DEAD in tsk->state and calls
+	 * schedule one last time. The schedule call will never return, and
+	 * the scheduled task must drop that reference.
+	 * The test for EXIT_DEAD must occur while the runqueue locks are
 	 * still held, otherwise prev could be scheduled on another cpu, die
 	 * there before we look at prev->state, and then the reference would
 	 * be dropped twice.
 	 *		Manfred Spraul <manfred@colorfullife.com>
 	 */
-	prev_task_flags = prev->flags;
+	prev_state = prev->state;
 	finish_arch_switch(prev);
 	finish_lock_switch(rq, prev);
 	if (mm)
 		mmdrop(mm);
-	if (unlikely(prev_task_flags & PF_DEAD)) {
+	if (unlikely(prev_state == EXIT_DEAD)) {
 		/*
 		 * Remove function-return probe instances associated with this
 		 * task and put them back on the free list.
@@ -5153,7 +5153,7 @@ static void migrate_dead(unsigned int dead_cpu, struct task_struct *p)
 	BUG_ON(p->exit_state != EXIT_ZOMBIE && p->exit_state != EXIT_DEAD);
 
 	/* Cannot have done final schedule yet: would have vanished. */
-	BUG_ON(p->flags & PF_DEAD);
+	BUG_ON(p->state == EXIT_DEAD);
 
 	get_task_struct(p);
 

mm/oom_kill.c

@@ -226,8 +226,8 @@ static struct task_struct *select_bad_process(unsigned long *ppoints)
 		releasing = test_tsk_thread_flag(p, TIF_MEMDIE) ||
 						p->flags & PF_EXITING;
 		if (releasing) {
-			/* PF_DEAD tasks have already released their mm */
-			if (p->flags & PF_DEAD)
+			/* TASK_DEAD tasks have already released their mm */
+			if (p->state == EXIT_DEAD)
 				continue;
 			if (p->flags & PF_EXITING && p == current) {
 				chosen = p;