From 94ddc7076d38c1ddbea48dda096b2a34e64f17e6 Mon Sep 17 00:00:00 2001
From: Alan Cox <alc@FreeBSD.org>
Date: Fri, 3 Sep 2004 05:11:32 +0000
Subject: [PATCH] Push Giant deep into vm_forkproc(), acquiring it only if the
 process has mapped System V shared memory segments (see shmfork_myhook()) or
 requires the allocation of an ldt (see vm_fault_wire()).

---
 sys/kern/kern_fork.c | 28 ++++++++++++----------------
 sys/kern/sysv_shm.c  |  2 ++
 sys/vm/vm_fault.c    |  4 ++++
 sys/vm/vm_glue.c     |  2 --
 sys/vm/vm_map.c      |  3 ---
 5 files changed, 18 insertions(+), 21 deletions(-)

diff --git a/sys/kern/kern_fork.c b/sys/kern/kern_fork.c
index 43a5595f28b5..b5459d8651aa 100644
--- a/sys/kern/kern_fork.c
+++ b/sys/kern/kern_fork.c
@@ -219,9 +219,7 @@ fork1(td, flags, pages, procp)
 	 * certain parts of a process from itself.
 	 */
 	if ((flags & RFPROC) == 0) {
-		mtx_lock(&Giant);
 		vm_forkproc(td, NULL, NULL, flags);
-		mtx_unlock(&Giant);
 
 		/*
 		 * Close all file descriptors.
@@ -668,27 +666,25 @@ fork1(td, flags, pages, procp)
 	 * Finish creating the child process.  It will return via a different
 	 * execution path later.  (ie: directly into user mode)
 	 */
-	mtx_lock(&Giant);
 	vm_forkproc(td, p2, td2, flags);
 
 	if (flags == (RFFDG | RFPROC)) {
-		cnt.v_forks++;
-		cnt.v_forkpages += p2->p_vmspace->vm_dsize +
-		    p2->p_vmspace->vm_ssize;
+		atomic_add_int(&cnt.v_forks, 1);
+		atomic_add_int(&cnt.v_forkpages, p2->p_vmspace->vm_dsize +
+		    p2->p_vmspace->vm_ssize);
 	} else if (flags == (RFFDG | RFPROC | RFPPWAIT | RFMEM)) {
-		cnt.v_vforks++;
-		cnt.v_vforkpages += p2->p_vmspace->vm_dsize +
-		    p2->p_vmspace->vm_ssize;
+		atomic_add_int(&cnt.v_vforks, 1);
+		atomic_add_int(&cnt.v_vforkpages, p2->p_vmspace->vm_dsize +
+		    p2->p_vmspace->vm_ssize);
 	} else if (p1 == &proc0) {
-		cnt.v_kthreads++;
-		cnt.v_kthreadpages += p2->p_vmspace->vm_dsize +
-		    p2->p_vmspace->vm_ssize;
+		atomic_add_int(&cnt.v_kthreads, 1);
+		atomic_add_int(&cnt.v_kthreadpages, p2->p_vmspace->vm_dsize +
+		    p2->p_vmspace->vm_ssize);
 	} else {
-		cnt.v_rforks++;
-		cnt.v_rforkpages += p2->p_vmspace->vm_dsize +
-		    p2->p_vmspace->vm_ssize;
+		atomic_add_int(&cnt.v_rforks, 1);
+		atomic_add_int(&cnt.v_rforkpages, p2->p_vmspace->vm_dsize +
+		    p2->p_vmspace->vm_ssize);
 	}
-	mtx_unlock(&Giant);
 
 	/*
 	 * Both processes are set up, now check if any loadable modules want
diff --git a/sys/kern/sysv_shm.c b/sys/kern/sysv_shm.c
index 2e807c912782..1173583bd1d9 100644
--- a/sys/kern/sysv_shm.c
+++ b/sys/kern/sysv_shm.c
@@ -806,6 +806,7 @@ shmfork_myhook(p1, p2)
 	size_t size;
 	int i;
 
+	mtx_lock(&Giant);
 	size = shminfo.shmseg * sizeof(struct shmmap_state);
 	shmmap_s = malloc(size, M_SHM, M_WAITOK);
 	bcopy(p1->p_vmspace->vm_shm, shmmap_s, size);
@@ -813,6 +814,7 @@ shmfork_myhook(p1, p2)
 	for (i = 0; i < shminfo.shmseg; i++, shmmap_s++)
 		if (shmmap_s->shmid != -1)
 			shmsegs[IPCID_TO_IX(shmmap_s->shmid)].shm_nattch++;
+	mtx_unlock(&Giant);
 }
 
 static void
diff --git a/sys/vm/vm_fault.c b/sys/vm/vm_fault.c
index b6e8b521726d..16f8272c0e90 100644
--- a/sys/vm/vm_fault.c
+++ b/sys/vm/vm_fault.c
@@ -1026,9 +1026,13 @@ vm_fault_wire(vm_map_t map, vm_offset_t start, vm_offset_t end,
 	 * read-only sections.
 	 */
 	for (va = start; va < end; va += PAGE_SIZE) {
+		if (map->system_map)
+			mtx_lock(&Giant);
 		rv = vm_fault(map, va,
 		    user_wire ? VM_PROT_READ : VM_PROT_READ | VM_PROT_WRITE,
 		    user_wire ? VM_FAULT_USER_WIRE : VM_FAULT_CHANGE_WIRING);
+		if (map->system_map)
+			mtx_unlock(&Giant);
 		if (rv) {
 			if (va != start)
 				vm_fault_unwire(map, start, va, fictitious);
diff --git a/sys/vm/vm_glue.c b/sys/vm/vm_glue.c
index 7893012f9c90..9d5fa42e1004 100644
--- a/sys/vm/vm_glue.c
+++ b/sys/vm/vm_glue.c
@@ -619,8 +619,6 @@ vm_forkproc(td, p2, td2, flags)
 {
 	struct proc *p1 = td->td_proc;
 
-	GIANT_REQUIRED;
-
 	if ((flags & RFPROC) == 0) {
 		/*
 		 * Divorce the memory, if it is shared, essentially
diff --git a/sys/vm/vm_map.c b/sys/vm/vm_map.c
index 2a486e8535d8..3788a4f119f1 100644
--- a/sys/vm/vm_map.c
+++ b/sys/vm/vm_map.c
@@ -2482,8 +2482,6 @@ vmspace_fork(struct vmspace *vm1)
 	vm_map_entry_t new_entry;
 	vm_object_t object;
 
-	GIANT_REQUIRED;
-
 	vm_map_lock(old_map);
 
 	vm2 = vmspace_alloc(old_map->min_offset, old_map->max_offset);
@@ -2942,7 +2940,6 @@ vmspace_unshare(struct proc *p)
 	struct vmspace *oldvmspace = p->p_vmspace;
 	struct vmspace *newvmspace;
 
-	GIANT_REQUIRED;
 	if (oldvmspace->vm_refcnt == 1)
 		return;
 	newvmspace = vmspace_fork(oldvmspace);