Giant pushdown for read/write/pread/pwrite syscalls.

kern/kern_descrip.c:
Aquire Giant in fdrop_locked when file refcount hits zero, this removes
the requirement for the caller to own Giant for the most part.

kern/kern_ktrace.c:
Aquire Giant in ktrgenio, simplifies locking in upper read/write syscalls.

kern/vfs_bio.c:
Aquire Giant in bwillwrite if needed.

kern/sys_generic.c
Giant pushdown, remove Giant for:
   read, pread, write and pwrite.
readv and writev aren't done yet because of the possible malloc calls
for iov to uio processing.

kern/sys_socket.c
Grab giant in the socket fo_read/write functions.

kern/vfs_vnops.c
Grab giant in the vnode fo_read/write functions.

1 files changed, 3 insertions, 0 deletions

diff --git a/sys/kern/kern_ktrace.c b/sys/kern/kern_ktrace.c
index 75372d8..c66108f 100644
--- a/sys/kern/kern_ktrace.c
+++ b/sys/kern/kern_ktrace.c
@@ -181,6 +181,8 @@ ktrgenio(vp, fd, rw, uio, error)
 
 	if (error)
 		return;
+
+	mtx_lock(&Giant);
 	/*
 	 * don't let p_tracep get ripped out from under us
 	 */
@@ -200,6 +202,7 @@ ktrgenio(vp, fd, rw, uio, error)
 		vrele(vp);
 	FREE(kth, M_KTRACE);
 	p->p_traceflag &= ~KTRFAC_ACTIVE;
+	mtx_unlock(&Giant);
 }
 
 void