With Alfred's permission, remove vm_mtx in favor of a fine-grained approach

(this commit is just the first stage).  Also add various GIANT_ macros to
formalize the removal of Giant, making it easy to test in a more piecemeal
fashion. These macros will allow us to test fine-grained locks to a degree
before removing Giant, and also after, and to remove Giant in a piecemeal
fashion via sysctl's on those subsystems which the authors believe can
operate without Giant.

1 files changed, 4 insertions, 13 deletions

diff --git a/sys/kern/imgact_elf.c b/sys/kern/imgact_elf.c
index fbb2a71..8cf2e24 100644
--- a/sys/kern/imgact_elf.c
+++ b/sys/kern/imgact_elf.c
@@ -198,6 +198,8 @@ elf_load_section(struct proc *p, struct vmspace *vmspace, struct vnode *vp, vm_o
 	vm_offset_t file_addr;
 	vm_offset_t data_buf = 0;
 
+	GIANT_REQUIRED;
+
 	VOP_GETVOBJECT(vp, &object);
 	error = 0;
 
@@ -230,7 +232,6 @@ elf_load_section(struct proc *p, struct vmspace *vmspace, struct vnode *vp, vm_o
 	else
 		map_len = round_page(offset+filsz) - file_addr;
 
-	mtx_lock(&vm_mtx);
 	if (map_len != 0) {
 		vm_object_reference(object);
 		vm_map_lock(&vmspace->vm_map);
@@ -245,13 +246,11 @@ elf_load_section(struct proc *p, struct vmspace *vmspace, struct vnode *vp, vm_o
 		vm_map_unlock(&vmspace->vm_map);
 		if (rv != KERN_SUCCESS) {
 			vm_object_deallocate(object);
-			mtx_unlock(&vm_mtx);
 			return EINVAL;
 		}
 
 		/* we can stop now if we've covered it all */
 		if (memsz == filsz) {
-			mtx_unlock(&vm_mtx);
 			return 0;
 		}
 	}
@@ -275,7 +274,6 @@ elf_load_section(struct proc *p, struct vmspace *vmspace, struct vnode *vp, vm_o
 					VM_PROT_ALL, VM_PROT_ALL, 0);
 		vm_map_unlock(&vmspace->vm_map);
 		if (rv != KERN_SUCCESS) {
-			mtx_unlock(&vm_mtx);
 			return EINVAL; 
 		}	
 	}
@@ -293,17 +291,13 @@ elf_load_section(struct proc *p, struct vmspace *vmspace, struct vnode *vp, vm_o
 				 MAP_COPY_ON_WRITE | MAP_PREFAULT_PARTIAL);
 		if (rv != KERN_SUCCESS) {
 			vm_object_deallocate(object);
-			mtx_unlock(&vm_mtx);
 			return EINVAL;
 		}
 
 		/* send the page fragment to user space */
-		mtx_unlock(&vm_mtx);
 		error = copyout((caddr_t)data_buf, (caddr_t)map_addr, copy_len);
-		mtx_lock(&vm_mtx);
 		vm_map_remove(exec_map, data_buf, data_buf + PAGE_SIZE);
 		if (error) {
-			mtx_unlock(&vm_mtx);
 			return (error);
 		}
 	}
@@ -314,7 +308,6 @@ elf_load_section(struct proc *p, struct vmspace *vmspace, struct vnode *vp, vm_o
 	vm_map_protect(&vmspace->vm_map, map_addr, map_addr + map_len,  prot,
 		       FALSE);
 
-	mtx_unlock(&vm_mtx);
 	return error;
 }
 
@@ -475,6 +468,8 @@ exec_elf_imgact(struct image_params *imgp)
 	Elf_Brandinfo *brand_info;
 	char path[MAXPATHLEN];
 
+	GIANT_REQUIRED;
+
 	/*
 	 * Do we have a valid ELF header ?
 	 */
@@ -510,11 +505,9 @@ exec_elf_imgact(struct image_params *imgp)
 	if ((error = exec_extract_strings(imgp)) != 0)
 		goto fail;
 
-	mtx_lock(&vm_mtx);
 	exec_new_vmspace(imgp);
 
 	vmspace = imgp->proc->p_vmspace;
-	mtx_unlock(&vm_mtx);
 
 	for (i = 0; i < hdr->e_phnum; i++) {
 		switch(phdr[i].p_type) {
@@ -571,12 +564,10 @@ exec_elf_imgact(struct image_params *imgp)
 		}
 	}
 
-	mtx_lock(&vm_mtx);
 	vmspace->vm_tsize = text_size >> PAGE_SHIFT;
 	vmspace->vm_taddr = (caddr_t)(uintptr_t)text_addr;
 	vmspace->vm_dsize = data_size >> PAGE_SHIFT;
 	vmspace->vm_daddr = (caddr_t)(uintptr_t)data_addr;
-	mtx_unlock(&vm_mtx);
 
 	addr = ELF_RTLD_ADDR(vmspace);