svn commit: r286256 - head/sys/kern

[John Baldwin]

Author: jhb
Date: Mon Aug  3 20:43:36 2015
New Revision: 286256
URL: https://svnweb.freebsd.org/changeset/base/286256

Log:
  kgdb uses td_oncpu to determine if a thread is running and should use
  a pcb from stoppcbs[] rather than the thread's PCB.  However, exited threads
  retained td_oncpu from the last time they ran, and newborn threads had their
  CPU fields cleared to zero during fork and thread creation since they are
  in the set of fields zeroed when threads are setup.  To fix, explicitly
  update the CPU fields for exiting threads in sched_throw() to reflect the
  switch out and reset the CPU fields for new threads in sched_fork_thread()
  to NOCPU.
  
  Reviewed by:	kib
  MFC after:	1 week
  Differential Revision:	https://reviews.freebsd.org/D3193

Modified:
  head/sys/kern/sched_4bsd.c
  head/sys/kern/sched_ule.c

Modified: head/sys/kern/sched_4bsd.c
==============================================================================
--- head/sys/kern/sched_4bsd.c	Mon Aug  3 20:30:27 2015	(r286255)
+++ head/sys/kern/sched_4bsd.c	Mon Aug  3 20:43:36 2015	(r286256)
@@ -792,6 +792,8 @@ sched_fork_thread(struct thread *td, str
 {
 	struct td_sched *ts;
 
+	childtd->td_oncpu = NOCPU;
+	childtd->td_lastcpu = NOCPU;
 	childtd->td_estcpu = td->td_estcpu;
 	childtd->td_lock = &sched_lock;
 	childtd->td_cpuset = cpuset_ref(td->td_cpuset);
@@ -1671,6 +1673,8 @@ sched_throw(struct thread *td)
 	} else {
 		lock_profile_release_lock(&sched_lock.lock_object);
 		MPASS(td->td_lock == &sched_lock);
+		td->td_lastcpu = td->td_oncpu;
+		td->td_oncpu = NOCPU;
 	}
 	mtx_assert(&sched_lock, MA_OWNED);
 	KASSERT(curthread->td_md.md_spinlock_count == 1, ("invalid count"));

Modified: head/sys/kern/sched_ule.c
==============================================================================
--- head/sys/kern/sched_ule.c	Mon Aug  3 20:30:27 2015	(r286255)
+++ head/sys/kern/sched_ule.c	Mon Aug  3 20:43:36 2015	(r286256)
@@ -2080,6 +2080,8 @@ sched_fork_thread(struct thread *td, str
 	 */
 	ts = td->td_sched;
 	ts2 = child->td_sched;
+	child->td_oncpu = NOCPU;
+	child->td_lastcpu = NOCPU;
 	child->td_lock = TDQ_LOCKPTR(tdq);
 	child->td_cpuset = cpuset_ref(td->td_cpuset);
 	ts2->ts_cpu = ts->ts_cpu;
@@ -2703,6 +2705,8 @@ sched_throw(struct thread *td)
 		MPASS(td->td_lock == TDQ_LOCKPTR(tdq));
 		tdq_load_rem(tdq, td);
 		lock_profile_release_lock(&TDQ_LOCKPTR(tdq)->lock_object);
+		td->td_lastcpu = td->td_oncpu;
+		td->td_oncpu = NOCPU;
 	}
 	KASSERT(curthread->td_md.md_spinlock_count == 1, ("invalid count"));
 	newtd = choosethread();