Some small fixes to CPU accounting for threads:

- Only initialize the per-cpu switchticks and switchtime in sched_throw()
  for the very first context switch on APs during boot.  This avoids a
  small gap between the middle of thread_exit() and sched_throw() where
  time is not accounted to any thread.
- In thread_exit(), update the timestamp bookkeeping to track the changes
  to mi_switch() introduced by td_rux so that the code once again matches
  the comment claiming it is mimicing mi_switch().  Specifically, only
  update the per-thread stats directly and depend on ruxagg() to update
  p_rux rather than adjusting p_rux directly.  While here, move the
  timestamp bookkeeping as late in the function as possible.

Reviewed by:	bde, kib
MFC after:	1 week

1 files changed, 2 insertions, 2 deletions

diff --git a/sys/kern/sched_4bsd.c b/sys/kern/sched_4bsd.c
index 0fd6481f9cfc..16cc033204e4 100644
--- a/sys/kern/sched_4bsd.c
+++ b/sys/kern/sched_4bsd.c
@@ -1572,14 +1572,14 @@ sched_throw(struct thread *td)
 	if (td == NULL) {
 		mtx_lock_spin(&sched_lock);
 		spinlock_exit();
+		PCPU_SET(switchtime, cpu_ticks());
+		PCPU_SET(switchticks, ticks);
 	} else {
 		lock_profile_release_lock(&sched_lock.lock_object);
 		MPASS(td->td_lock == &sched_lock);
 	}
 	mtx_assert(&sched_lock, MA_OWNED);
 	KASSERT(curthread->td_md.md_spinlock_count == 1, ("invalid count"));
-	PCPU_SET(switchtime, cpu_ticks());
-	PCPU_SET(switchticks, ticks);
 	cpu_throw(td, choosethread());	/* doesn't return */
 }