From b99aa0fbb203fa85c8be47b883449d6516393c66 Mon Sep 17 00:00:00 2001
From: Matt Macy <mmacy@FreeBSD.org>
Date: Tue, 29 May 2018 18:03:48 +0000
Subject: [PATCH] hwpmc: don't enter epoch section across mmap hook

---
 sys/dev/hwpmc/hwpmc_mod.c | 3 ++-
 sys/kern/vfs_vnops.c      | 2 +-
 sys/sys/pmckern.h         | 3 ++-
 3 files changed, 5 insertions(+), 3 deletions(-)

diff --git a/sys/dev/hwpmc/hwpmc_mod.c b/sys/dev/hwpmc/hwpmc_mod.c
index ba9f0cff19b..dab8dfe789a 100644
--- a/sys/dev/hwpmc/hwpmc_mod.c
+++ b/sys/dev/hwpmc/hwpmc_mod.c
@@ -1717,7 +1717,7 @@ pmc_process_mmap(struct thread *td, struct pmckern_map_in *pkm)
 	const struct pmc_process *pp;
 
 	freepath = fullpath = NULL;
-	epoch_exit_preempt(global_epoch_preempt);
+	MPASS(!in_epoch());
 	pmc_getfilename((struct vnode *) pkm->pm_file, &fullpath, &freepath);
 
 	pid = td->td_proc->p_pid;
@@ -1743,6 +1743,7 @@ pmc_process_mmap(struct thread *td, struct pmckern_map_in *pkm)
   done:
 	if (freepath)
 		free(freepath, M_TEMP);
+	epoch_exit_preempt(global_epoch_preempt);
 }
 
 
diff --git a/sys/kern/vfs_vnops.c b/sys/kern/vfs_vnops.c
index 5d3efc7a820..f8fb7ca4c12 100644
--- a/sys/kern/vfs_vnops.c
+++ b/sys/kern/vfs_vnops.c
@@ -2494,7 +2494,7 @@ vn_mmap(struct file *fp, vm_map_t map, vm_offset_t *addr, vm_size_t size,
 		if ((prot & VM_PROT_EXECUTE) != 0 && error == 0) {
 			pkm.pm_file = vp;
 			pkm.pm_address = (uintptr_t) *addr;
-			PMC_CALL_HOOK(td, PMC_FN_MMAP, (void *) &pkm);
+			PMC_CALL_HOOK_UNLOCKED(td, PMC_FN_MMAP, (void *) &pkm);
 		}
 	}
 #endif
diff --git a/sys/sys/pmckern.h b/sys/sys/pmckern.h
index a0e59b99ed4..da2aae5fc84 100644
--- a/sys/sys/pmckern.h
+++ b/sys/sys/pmckern.h
@@ -217,7 +217,8 @@ do {						\
  */
 #define	PMC_CALL_HOOK_UNLOCKED(t, cmd, arg)	\
 do {						\
-	if (pmc_hook != NULL)			\
+	MPASS(!in_epoch());					\
+	if (pmc_hook != NULL)				\
 		(pmc_hook)((t), (cmd), (arg));	\
 } while (0)