timers: fix itimer/many thread hang, v2

This is the second resubmission of the posix timer rework patch, posted
a few days ago.

This includes the changes from the previous resubmittion, which addressed
Oleg Nesterov's comments, removing the RCU stuff from the patch and
un-inlining the thread_group_cputime() function for SMP.

In addition, per Ingo Molnar it simplifies the UP code, consolidating much
of it with the SMP version and depending on lower-level SMP/UP handling to
take care of the differences.

It also cleans up some UP compile errors, moves the scheduler stats-related
macros into kernel/sched_stats.h, cleans up a merge error in
kernel/fork.c and has a few other minor fixes and cleanups as suggested
by Oleg and Ingo. Thanks for the review, guys.

Signed-off-by: Frank Mayhar <fmayhar@google.com>
Cc: Roland McGrath <roland@redhat.com>
Cc: Alexey Dobriyan <adobriyan@gmail.com>
Cc: Andrew Morton <akpm@linux-foundation.org>
Signed-off-by: Ingo Molnar <mingo@elte.hu>

1 files changed, 7 insertions, 40 deletions

diff --git a/kernel/sched.c b/kernel/sched.c
index c51b5d27666..260c22cc530 100644
--- a/kernel/sched.c
+++ b/kernel/sched.c
@@ -4039,55 +4039,22 @@ EXPORT_PER_CPU_SYMBOL(kstat);
 /*
  * Return any ns on the sched_clock that have not yet been banked in
  * @p in case that task is currently running.
- *
- * Called with task_rq_lock() held on @rq.
  */
-static unsigned long long task_delta_exec(struct task_struct *p, struct rq *rq)
+unsigned long long task_delta_exec(struct task_struct *p)
 {
+	struct rq *rq;
+	unsigned long flags;
+	u64 ns = 0;
+
+	rq = task_rq_lock(p, &flags);
 	if (task_current(rq, p)) {
 		u64 delta_exec;
 
 		update_rq_clock(rq);
 		delta_exec = rq->clock - p->se.exec_start;
 		if ((s64)delta_exec > 0)
-			return delta_exec;
+			ns = delta_exec;
 	}
-	return 0;
-}
-
-/*
- * Return p->sum_exec_runtime plus any more ns on the sched_clock
- * that have not yet been banked in case the task is currently running.
- */
-unsigned long long task_sched_runtime(struct task_struct *p)
-{
-	unsigned long flags;
-	u64 ns;
-	struct rq *rq;
-
-	rq = task_rq_lock(p, &flags);
-	ns = p->se.sum_exec_runtime + task_delta_exec(p, rq);
-	task_rq_unlock(rq, &flags);
-
-	return ns;
-}
-
-/*
- * Return sum_exec_runtime for the thread group plus any more ns on the
- * sched_clock that have not yet been banked in case the task is currently
- * running.
- */
-unsigned long long thread_group_sched_runtime(struct task_struct *p)
-{
-	unsigned long flags;
-	u64 ns;
-	struct rq *rq;
-	struct task_cputime totals;
-
-	rq = task_rq_lock(p, &flags);
-	thread_group_cputime(p, &totals);
-	ns = totals.sum_exec_runtime + task_delta_exec(p, rq);
-	task_rq_unlock(rq, &flags);
 
 	return ns;
 }