Make uio_yield() a global. Call uio_yield() between chunks

in vn_rdwr_inchunks(), allowing other processes to gain an exclusive
lock on the vnode.  Specifically: directory scanning, to avoid a race to the
root directory, and multiple child processes coring simultaniously so they
can figure out that some other core'ing child has an exclusive adv lock and
just exit instead.

This completely fixes performance problems when large programs core.  You
can have hundreds of copies (forked children) of the same binary core all
at once and not notice.

MFC after:	3 days

1 files changed, 1 insertions, 3 deletions

diff --git a/sys/kern/kern_subr.c b/sys/kern/kern_subr.c
index 9f53d2d..cab78c2 100644
--- a/sys/kern/kern_subr.c
+++ b/sys/kern/kern_subr.c
@@ -55,8 +55,6 @@
 #include <vm/vm_page.h>
 #include <vm/vm_map.h>
 
-static void	uio_yield __P((void));
-
 SYSCTL_INT(_kern, KERN_IOV_MAX, iov_max, CTLFLAG_RD, NULL, UIO_MAXIOV, 
 	"Maximum number of elements in an I/O vector; sysconf(_SC_IOV_MAX)");
 
@@ -381,7 +379,7 @@ phashinit(elements, type, nentries)
 	return (hashtbl);
 }
 
-static void
+void
 uio_yield()
 {
 	struct thread *td;