Introduce a global lock for the vm subsystem (vm_mtx).

vm_mtx does not recurse and is required for most low level
vm operations.

faults can not be taken without holding Giant.

Memory subsystems can now call the base page allocators safely.

Almost all atomic ops were removed as they are covered under the
vm mutex.

Alpha and ia64 now need to catch up to i386's trap handlers.

FFS and NFS have been tested, other filesystems will need minor
changes (grabbing the vm lock when twiddling page properties).

Reviewed (partially) by: jake, jhb

1 files changed, 7 insertions, 6 deletions

diff --git a/sys/kern/subr_trap.c b/sys/kern/subr_trap.c
index af7bfc1..8924fa2 100644
--- a/sys/kern/subr_trap.c
+++ b/sys/kern/subr_trap.c
@@ -330,9 +330,7 @@ restart:
 			 */
 			eva = rcr2();
 			enable_intr();
-			mtx_lock(&Giant);
 			i = trap_pfault(&frame, TRUE, eva);
-			mtx_unlock(&Giant);
 #if defined(I586_CPU) && !defined(NO_F00F_HACK)
 			if (i == -2) {
 				/*
@@ -443,9 +441,7 @@ restart:
 			 */
 			eva = rcr2();
 			enable_intr();
-			mtx_lock(&Giant);
 			(void) trap_pfault(&frame, FALSE, eva);
-			mtx_unlock(&Giant);
 			goto out;
 
 		case T_DNA:
@@ -887,7 +883,9 @@ nogo:
 			frame->tf_eip = (int)PCPU_GET(curpcb)->pcb_onfault;
 			return (0);
 		}
+		mtx_lock(&Giant);
 		trap_fatal(frame, eva);
+		mtx_unlock(&Giant);
 		return (-1);
 	}
 
@@ -1147,14 +1145,17 @@ syscall(frame)
 
 	/*
 	 * Try to run the syscall without the MP lock if the syscall
-	 * is MP safe.  We have to obtain the MP lock no matter what if 
-	 * we are ktracing
+	 * is MP safe.
 	 */
 	if ((callp->sy_narg & SYF_MPSAFE) == 0) {
 		mtx_lock(&Giant);
 	}
 
 #ifdef KTRACE
+	/*
+	 * We have to obtain the MP lock no matter what if 
+	 * we are ktracing
+	 */
 	if (KTRPOINT(p, KTR_SYSCALL)) {
 		if (!mtx_owned(&Giant))
 			mtx_lock(&Giant);