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, 2 insertions, 0 deletions

diff --git a/sys/kern/kern_descrip.c b/sys/kern/kern_descrip.c
index 5fed676..50bcc3a 100644
--- a/sys/kern/kern_descrip.c
+++ b/sys/kern/kern_descrip.c
@@ -1716,6 +1716,7 @@ fdrop_locked(fp, td)
 		FILE_UNLOCK(fp);
 		return (0);
 	}
+	mtx_lock(&Giant);
 	if (fp->f_count < 0)
 		panic("fdrop: count < 0");
 	if ((fp->f_flag & FHASLOCK) && fp->f_type == DTYPE_VNODE) {
@@ -1733,6 +1734,7 @@ fdrop_locked(fp, td)
 	else
 		error = 0;
 	ffree(fp);
+	mtx_unlock(&Giant);
 	return (error);
 }