Index: sys/sparc64/pci/schizo.c
===================================================================
--- sys/sparc64/pci/schizo.c	(revisione 242468)
+++ sys/sparc64/pci/schizo.c	(copia locale)
@@ -51,6 +51,7 @@ __FBSDID("$FreeBSD$");
 #include <sys/module.h>
 #include <sys/mutex.h>
 #include <sys/pcpu.h>
+#include <sys/proc.h>
 #include <sys/rman.h>
 #include <sys/sysctl.h>
 #include <sys/time.h>
Index: sys/sparc64/pci/fire.c
===================================================================
--- sys/sparc64/pci/fire.c	(revisione 242468)
+++ sys/sparc64/pci/fire.c	(copia locale)
@@ -53,6 +53,7 @@ __FBSDID("$FreeBSD$");
 #include <sys/mutex.h>
 #include <sys/pciio.h>
 #include <sys/pcpu.h>
+#include <sys/proc.h>
 #include <sys/rman.h>
 #include <sys/smp.h>
 #include <sys/sysctl.h>
Index: sys/i386/i386/i686_mem.c
===================================================================
--- sys/i386/i386/i686_mem.c	(revisione 242468)
+++ sys/i386/i386/i686_mem.c	(copia locale)
@@ -32,6 +32,7 @@ __FBSDID("$FreeBSD$");
 #include <sys/systm.h>
 #include <sys/malloc.h>
 #include <sys/memrange.h>
+#include <sys/proc.h>
 #include <sys/smp.h>
 #include <sys/sysctl.h>
 
Index: sys/i386/pci/pci_cfgreg.c
===================================================================
--- sys/i386/pci/pci_cfgreg.c	(revisione 242468)
+++ sys/i386/pci/pci_cfgreg.c	(copia locale)
@@ -39,6 +39,7 @@ __FBSDID("$FreeBSD$");
 #include <sys/kernel.h>
 #include <sys/mutex.h>
 #include <sys/malloc.h>
+#include <sys/proc.h>
 #include <sys/queue.h>
 #include <sys/sysctl.h>
 #include <dev/pci/pcivar.h>
Index: sys/amd64/amd64/amd64_mem.c
===================================================================
--- sys/amd64/amd64/amd64_mem.c	(revisione 242468)
+++ sys/amd64/amd64/amd64_mem.c	(copia locale)
@@ -32,6 +32,7 @@ __FBSDID("$FreeBSD$");
 #include <sys/systm.h>
 #include <sys/malloc.h>
 #include <sys/memrange.h>
+#include <sys/proc.h>
 #include <sys/smp.h>
 #include <sys/sysctl.h>
 
Index: sys/sys/buf_ring.h
===================================================================
--- sys/sys/buf_ring.h	(revisione 242468)
+++ sys/sys/buf_ring.h	(copia locale)
@@ -30,6 +30,8 @@
 #ifndef	_SYS_BUF_RING_H_
 #define	_SYS_BUF_RING_H_
 
+#include <sys/proc.h>
+
 #include <machine/cpu.h>
 
 #if defined(INVARIANTS) && !defined(DEBUG_BUFRING)
Index: sys/sys/systm.h
===================================================================
--- sys/sys/systm.h	(revisione 242468)
+++ sys/sys/systm.h	(copia locale)
@@ -171,10 +171,24 @@ void	g_waitidle(void);
 
 void	panic(const char *, ...) __dead2 __printflike(1, 2);
 
+void	_critical_enter(const char *, int);
+
+#define	_critical_acquire(td)	((td)->td_critnest++)
+
+#define	_critical_enter_fast() do {					\
+	_critical_acquire(curthread);					\
+	__compiler_membar();						\
+} while (0)
+
+#ifdef KTR
+#define	critical_enter()	_critical_enter(__FILE__, __LINE__)
+#else
+#define	critical_enter()	_critical_enter_fast()
+#endif
+
 void	cpu_boot(int);
 void	cpu_flush_dcache(void *, size_t);
 void	cpu_rootconf(void);
-void	critical_enter(void);
 void	critical_exit(void);
 void	init_param1(void);
 void	init_param2(long physpages);
Index: sys/kern/kern_switch.c
===================================================================
--- sys/kern/kern_switch.c	(revisione 242468)
+++ sys/kern/kern_switch.c	(copia locale)
@@ -174,20 +174,28 @@ retry:
 }
 
 /*
- * Kernel thread preemption implementation.  Critical sections mark
+ * Kernel thread preemption implementation, hard path.  Critical sections mark
  * regions of code in which preemptions are not allowed.
  */
 void
-critical_enter(void)
+_critical_enter(const char *file, int line)
 {
 	struct thread *td;
 
 	td = curthread;
-	td->td_critnest++;
-	CTR4(KTR_CRITICAL, "critical_enter by thread %p (%ld, %s) to %d", td,
-	    (long)td->td_proc->p_pid, td->td_name, td->td_critnest);
+	_critical_acquire(td);
+	CTR6(KTR_CRITICAL, "critical_enter: thread %p (%ld, %s) to %d @ %s:%d",
+	    td, (long)td->td_proc->p_pid, td->td_name, td->td_critnest, file,
+	    line);
 }
 
+/*
+ * Mark the end of critical section.
+ * This function has not a fast version because nested critical sections are
+ * pretty much rare and then a function call will happen anyway (besides other
+ * minor factor to carefully evaluate like possible branch misprediction,
+ * performance burden of __compile_membar(), text size increase, etc.).
+ */
 void
 critical_exit(void)
 {
Index: sys/kern/subr_smp.c
===================================================================
--- sys/kern/subr_smp.c	(revisione 242468)
+++ sys/kern/subr_smp.c	(copia locale)
@@ -368,7 +368,7 @@ smp_rendezvous_action(void)
 	 * during this routine.
 	 */
 	td = curthread;
-	td->td_critnest++;
+	critical_enter();
 #ifdef INVARIANTS
 	owepreempt = td->td_owepreempt;
 #endif
Index: sys/kern/kern_rmlock.c
===================================================================
--- sys/kern/kern_rmlock.c	(revisione 242468)
+++ sys/kern/kern_rmlock.c	(copia locale)
@@ -347,10 +347,8 @@ _rm_rlock(struct rmlock *rm, struct rm_priotracker
 	tracker->rmp_thread = td;
 	tracker->rmp_rmlock = rm;
 
-	td->td_critnest++;	/* critical_enter(); */
+	critical_enter();
 
-	__compiler_membar();
-
 	pc = cpuid_to_pcpu[td->td_oncpu]; /* pcpu_find(td->td_oncpu); */
 
 	rm_tracker_add(pc, tracker);
@@ -415,7 +413,7 @@ _rm_runlock(struct rmlock *rm, struct rm_priotrack
 	if (SCHEDULER_STOPPED())
 		return;
 
-	td->td_critnest++;	/* critical_enter(); */
+	critical_enter();
 	pc = cpuid_to_pcpu[td->td_oncpu]; /* pcpu_find(td->td_oncpu); */
 	rm_tracker_remove(pc, tracker);
 	td->td_critnest--;
Index: sys/mips/nlm/tick.c
===================================================================
--- sys/mips/nlm/tick.c	(revisione 242468)
+++ sys/mips/nlm/tick.c	(copia locale)
@@ -43,6 +43,7 @@ __FBSDID("$FreeBSD$");
 #include <sys/module.h>
 #include <sys/rman.h>
 #include <sys/power.h>
+#include <sys/proc.h>
 #include <sys/smp.h>
 #include <sys/time.h>
 #include <sys/timeet.h>
Index: sys/mips/nlm/intr_machdep.c
===================================================================
--- sys/mips/nlm/intr_machdep.c	(revisione 242468)
+++ sys/mips/nlm/intr_machdep.c	(copia locale)
@@ -35,6 +35,7 @@ __FBSDID("$FreeBSD$");
 #include <sys/bus.h>
 #include <sys/interrupt.h>
 #include <sys/kernel.h>
+#include <sys/proc.h>
 
 #include <machine/cpu.h>
 #include <machine/cpufunc.h>
Index: sys/mips/mips/tick.c
===================================================================
--- sys/mips/mips/tick.c	(revisione 242468)
+++ sys/mips/mips/tick.c	(copia locale)
@@ -41,6 +41,7 @@ __FBSDID("$FreeBSD$");
 #include <sys/module.h>
 #include <sys/rman.h>
 #include <sys/power.h>
+#include <sys/proc.h>
 #include <sys/smp.h>
 #include <sys/time.h>
 #include <sys/timeet.h>
Index: sys/dev/scd/scd.c
===================================================================
--- sys/dev/scd/scd.c	(revisione 242468)
+++ sys/dev/scd/scd.c	(copia locale)
@@ -55,6 +55,7 @@ __FBSDID("$FreeBSD$");
 #include <sys/cdio.h>
 #include <sys/disk.h>
 #include <sys/bus.h>
+#include <sys/proc.h>
 
 #include <machine/stdarg.h>
 
Index: sys/dev/mcd/mcd.c
===================================================================
--- sys/dev/mcd/mcd.c	(revisione 242468)
+++ sys/dev/mcd/mcd.c	(copia locale)
@@ -55,6 +55,7 @@ static const char COPYRIGHT[] = "mcd-driver (C)199
 #include <sys/cdio.h>
 #include <sys/disk.h>
 #include <sys/bus.h>
+#include <sys/proc.h>
 
 #include <machine/bus.h>
 #include <machine/resource.h>
Index: sys/dev/glxiic/glxiic.c
===================================================================
--- sys/dev/glxiic/glxiic.c	(revisione 242468)
+++ sys/dev/glxiic/glxiic.c	(copia locale)
@@ -42,6 +42,7 @@ __FBSDID("$FreeBSD$");
 #include <sys/module.h>
 #include <sys/lock.h>
 #include <sys/mutex.h>
+#include <sys/proc.h>
 #include <sys/sysctl.h>
 #ifdef GLXIIC_DEBUG
 #include <sys/syslog.h>