Removed sched_nest variable in sched_switch(). Context switches always

begin with sched_lock held but not recursed, so this variable was
always 0.

Removed fixup of sched_lock.mtx_recurse after context switches in
sched_switch().  Context switches always end with this variable in the
same state that it began in, so there is no need to fix it up.  Only
sched_lock.mtx_lock really needs a fixup.

Replaced fixup of sched_lock.mtx_recurse in fork_exit() by an assertion
that sched_lock is owned and not recursed after it is fixed up.  This
assertion much match the one in mi_switch(), and if sched_lock were
recursed then a non-null fixup of sched_lock.mtx_recurse would probably
be needed again, unlike in sched_switch(), since fork_exit() doesn't
return to its caller in the normal way.

3 files changed, 1 insertions, 7 deletions

diff --git a/sys/kern/kern_fork.c b/sys/kern/kern_fork.c
index 5330dcd..94b2553 100644
--- a/sys/kern/kern_fork.c
+++ b/sys/kern/kern_fork.c
@@ -778,7 +778,7 @@ fork_exit(callout, arg, frame)
 	 * non-nested critical section with sched_lock held but not recursed.
 	 */
 	sched_lock.mtx_lock = (uintptr_t)td;
-	sched_lock.mtx_recurse = 0;
+	mtx_assert(&sched_lock, MA_OWNED | MA_NOTRECURSED);
 	cpu_critical_fork_exit();
 	CTR3(KTR_PROC, "fork_exit: new thread %p (pid %d, %s)", td, p->p_pid,
 	    p->p_comm);
diff --git a/sys/kern/sched_4bsd.c b/sys/kern/sched_4bsd.c
index 6480b49..1a23157 100644
--- a/sys/kern/sched_4bsd.c
+++ b/sys/kern/sched_4bsd.c
@@ -567,7 +567,6 @@ void
 sched_switch(struct thread *td)
 {
 	struct thread *newtd;
-	u_long sched_nest;
 	struct kse *ke;
 	struct proc *p;
 
@@ -597,11 +596,9 @@ sched_switch(struct thread *td)
 		 */
 		kse_reassign(ke);
 	}
-	sched_nest = sched_lock.mtx_recurse;
 	newtd = choosethread();
 	if (td != newtd)
 		cpu_switch(td, newtd);
-	sched_lock.mtx_recurse = sched_nest;
 	sched_lock.mtx_lock = (uintptr_t)td;
 	td->td_oncpu = PCPU_GET(cpuid);
 }
diff --git a/sys/kern/sched_ule.c b/sys/kern/sched_ule.c
index a41d712..c8c4618 100644
--- a/sys/kern/sched_ule.c
+++ b/sys/kern/sched_ule.c
@@ -806,7 +806,6 @@ void
 sched_switch(struct thread *td)
 {
 	struct thread *newtd;
-	u_int sched_nest;
 	struct kse *ke;
 
 	mtx_assert(&sched_lock, MA_OWNED);
@@ -847,11 +846,9 @@ sched_switch(struct thread *td)
 		if (td->td_proc->p_flag & P_SA)
 			kse_reassign(ke);
 	}
-	sched_nest = sched_lock.mtx_recurse;
 	newtd = choosethread();
 	if (td != newtd)
 		cpu_switch(td, newtd);
-	sched_lock.mtx_recurse = sched_nest;
 	sched_lock.mtx_lock = (uintptr_t)td;
 
 	td->td_oncpu = PCPU_GET(cpuid);