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, 12 insertions, 2 deletions

diff --git a/sys/kern/sys_socket.c b/sys/kern/sys_socket.c
index 13f4000..c8a6198 100644
--- a/sys/kern/sys_socket.c
+++ b/sys/kern/sys_socket.c
@@ -65,7 +65,12 @@ soo_read(fp, uio, cred, flags, td)
 	int flags;
 {
 	struct socket *so = (struct socket *)fp->f_data;
-	return so->so_proto->pr_usrreqs->pru_soreceive(so, 0, uio, 0, 0, 0);
+	int error;
+
+	mtx_lock(&Giant);
+	error = so->so_proto->pr_usrreqs->pru_soreceive(so, 0, uio, 0, 0, 0);
+	mtx_unlock(&Giant);
+	return (error);
 }
 
 /* ARGSUSED */
@@ -78,8 +83,13 @@ soo_write(fp, uio, cred, flags, td)
 	int flags;
 {
 	struct socket *so = (struct socket *)fp->f_data;
-	return so->so_proto->pr_usrreqs->pru_sosend(so, 0, uio, 0, 0, 0,
+	int error;
+
+	mtx_lock(&Giant);
+	error = so->so_proto->pr_usrreqs->pru_sosend(so, 0, uio, 0, 0, 0,
 						    uio->uio_td);
+	mtx_unlock(&Giant);
+	return (error);
 }
 
 int