Index: sys/dev/hwpmc/hwpmc_mod.c
===================================================================
--- sys/dev/hwpmc/hwpmc_mod.c
+++ sys/dev/hwpmc/hwpmc_mod.c
@@ -142,8 +142,7 @@
 
 
 /* various event handlers */
-static eventhandler_tag	pmc_exit_tag, pmc_fork_tag, pmc_kld_load_tag,
-    pmc_kld_unload_tag;
+static eventhandler_tag	pmc_kld_load_tag, pmc_kld_unload_tag;
 
 /* Module statistics */
 struct pmc_driverstats pmc_stats;
@@ -239,9 +238,8 @@
 static void	pmc_maybe_remove_owner(struct pmc_owner *po);
 static void	pmc_process_csw_in(struct thread *td);
 static void	pmc_process_csw_out(struct thread *td);
-static void	pmc_process_exit(void *arg, struct proc *p);
-static void	pmc_process_fork(void *arg, struct proc *p1,
-    struct proc *p2, int n);
+static void	pmc_process_exit(struct proc *p);
+static void	pmc_process_fork(struct proc *p1, struct proc *p2);
 static void	pmc_process_samples(int cpu, ring_type_t soft);
 static void	pmc_release_pmc_descriptor(struct pmc *pmc);
 static void	pmc_process_thread_add(struct thread *td);
@@ -2091,10 +2089,13 @@
 
 	switch (function)
 	{
+	case PMC_FN_PROCESS_EXIT:
+		pmc_process_exit(td->td_proc);
+		break;
 
-	/*
-	 * Process exec()
-	 */
+	case PMC_FN_PROCESS_FORK:
+		pmc_process_fork(td->td_proc, (struct proc *)arg);
+		break;
 
 	case PMC_FN_PROCESS_EXEC:
 	{
@@ -5057,7 +5058,7 @@
  */
 
 static void
-pmc_process_exit(void *arg __unused, struct proc *p)
+pmc_process_exit(struct proc *p)
 {
 	struct pmc *pm;
 	int adjri, cpu;
@@ -5240,8 +5241,7 @@
  */
 
 static void
-pmc_process_fork(void *arg __unused, struct proc *p1, struct proc *newproc,
-    int flags)
+pmc_process_fork(struct proc *p1, struct proc *newproc)
 {
 	int is_using_hwpmcs;
 	unsigned int ri;
@@ -5250,8 +5250,6 @@
 	struct pmc_owner *po;
 	struct pmc_process *ppnew, *ppold;
 
-	(void) flags;		/* unused parameter */
-
 	PROC_LOCK(p1);
 	is_using_hwpmcs = p1->p_flag & P_HWPMC;
 	PROC_UNLOCK(p1);
@@ -5720,12 +5718,6 @@
 	/* Initialize the task to prune the thread free list. */
 	TASK_INIT(&free_task, 0, pmc_thread_descriptor_pool_free_task, NULL);
 
-	/* register process {exit,fork,exec} handlers */
-	pmc_exit_tag = EVENTHANDLER_REGISTER(process_exit,
-	    pmc_process_exit, NULL, EVENTHANDLER_PRI_ANY);
-	pmc_fork_tag = EVENTHANDLER_REGISTER(process_fork,
-	    pmc_process_fork, NULL, EVENTHANDLER_PRI_ANY);
-
 	/* register kld event handlers */
 	pmc_kld_load_tag = EVENTHANDLER_REGISTER(kld_load, pmc_kld_load,
 	    NULL, EVENTHANDLER_PRI_ANY);
@@ -5769,9 +5761,11 @@
 	struct pmc_ownerhash *ph;
 	struct pmc_owner *po, *tmp;
 	struct pmc_binding pb;
+	struct proc *p, *phead;
 #ifdef	HWPMC_DEBUG
 	struct pmc_processhash *prh;
 #endif
+	bool draining;
 
 	PMCDBG0(MOD,INI,0, "cleanup");
 
@@ -5786,11 +5780,40 @@
 		return;
 	}
 
+	/*
+	 * Ensure that fork and exit hooks are not called.
+	 * New forked processes are added at the head of allproc p_list.
+	 * There is no need to drain processes before phead in allproc,
+	 * they were forked after pmc_hook was cleared.
+	 */
+	sx_slock(&allproc_lock);
 	pmc_hook = NULL; /* prevent new threads from entering module */
 
+	phead = LIST_FIRST(&allproc);
+	for (;;) {
+		draining = false;
+		p = phead;
+		LIST_FOREACH_FROM(p, &allproc, p_list) {
+			PROC_LOCK(p);
+			if (p->p_state == PRS_NEW ||
+			    ((p->p_flag & P_WEXIT) != 0 &&
+			    p->p_state != PRS_ZOMBIE))
+				draining = true;
+			PROC_UNLOCK(p);
+			if (draining)
+				break;
+		}
+		if (draining) {
+			sx_sunlock(&allproc_lock);
+			pause("hwpmcd", 1);
+			sx_slock(&allproc_lock);
+		}
+		else
+			break;
+	}
+	sx_sunlock(&allproc_lock);
+
 	/* deregister event handlers */
-	EVENTHANDLER_DEREGISTER(process_fork, pmc_fork_tag);
-	EVENTHANDLER_DEREGISTER(process_exit, pmc_exit_tag);
 	EVENTHANDLER_DEREGISTER(kld_load, pmc_kld_load_tag);
 	EVENTHANDLER_DEREGISTER(kld_unload, pmc_kld_unload_tag);
 
Index: sys/kern/kern_exit.c
===================================================================
--- sys/kern/kern_exit.c
+++ sys/kern/kern_exit.c
@@ -39,6 +39,7 @@
 #include <sys/cdefs.h>
 __FBSDID("$FreeBSD$");
 
+#include "opt_hwpmc_hooks.h"
 #include "opt_ktrace.h"
 
 #include <sys/param.h>
@@ -73,6 +74,7 @@
 #include <sys/shm.h>
 #include <sys/sem.h>
 #include <sys/sysent.h>
+#include <sys/pmckern.h>
 #include <sys/timers.h>
 #include <sys/umtx.h>
 #ifdef KTRACE
@@ -331,6 +333,10 @@
 	if (p->p_sysent->sv_onexit != NULL)
 		p->p_sysent->sv_onexit(p);
 
+#ifdef	HWPMC_HOOKS
+	PMC_CALL_HOOK_UNLOCKED(td, PMC_FN_PROCESS_EXIT, NULL);
+#endif
+
 	/*
 	 * Check if any loadable modules need anything done at process exit.
 	 * E.g. SYSV IPC stuff.
Index: sys/kern/kern_fork.c
===================================================================
--- sys/kern/kern_fork.c
+++ sys/kern/kern_fork.c
@@ -39,6 +39,7 @@
 #include <sys/cdefs.h>
 __FBSDID("$FreeBSD$");
 
+#include "opt_hwpmc_hooks.h"
 #include "opt_ktrace.h"
 #include "opt_kstack_pages.h"
 
@@ -56,6 +57,7 @@
 #include <sys/lock.h>
 #include <sys/malloc.h>
 #include <sys/mutex.h>
+#include <sys/pmckern.h>
 #include <sys/priv.h>
 #include <sys/proc.h>
 #include <sys/procdesc.h>
@@ -672,6 +674,10 @@
 	if (fr->fr_flags & RFPROCDESC)
 		procdesc_new(p2, fr->fr_pd_flags);
 
+#ifdef	HWPMC_HOOKS
+	PMC_CALL_HOOK_UNLOCKED(td, PMC_FN_PROCESS_FORK, p2);
+#endif
+
 	/*
 	 * Both processes are set up, now check if any loadable modules want
 	 * to adjust anything.
Index: sys/sys/pmckern.h
===================================================================
--- sys/sys/pmckern.h
+++ sys/sys/pmckern.h
@@ -53,8 +53,8 @@
 #define	PMC_FN_CSW_IN			2
 #define	PMC_FN_CSW_OUT			3
 #define	PMC_FN_DO_SAMPLES		4
-#define	PMC_FN_UNUSED1			5
-#define	PMC_FN_UNUSED2			6
+#define	PMC_FN_PROCESS_EXIT		5
+#define	PMC_FN_PROCESS_FORK		6
 #define	PMC_FN_MMAP			7
 #define	PMC_FN_MUNMAP			8
 #define	PMC_FN_USER_CALLCHAIN		9