Module Name: src
Committed By: hannken
Date: Tue Nov 9 16:31:48 UTC 2010
Modified Files:
src/sys/miscfs/genfs: genfs_io.c
Log Message:
Genfs_getpages(): Break a deadlock where one thread runs VOP_GETPAGES(),
has busy pages and wants the wapbl lock as reader from wapbl_begin(),
another thread has the wapbl lock as reader and waits for a page from
the first thread. Now a third thread calls wapbl_flush() and wants the
wapbl lock as writer.
Move the wapbl_begin() up to a point where genfs_getpages() has no busy
pages yet.
To generate a diff of this commit:
cvs rdiff -u -r1.41 -r1.42 src/sys/miscfs/genfs/genfs_io.c
Please note that diffs are not public domain; they are subject to the
copyright notices on the relevant files.
Modified files:
Index: src/sys/miscfs/genfs/genfs_io.c
diff -u src/sys/miscfs/genfs/genfs_io.c:1.41 src/sys/miscfs/genfs/genfs_io.c:1.42
--- src/sys/miscfs/genfs/genfs_io.c:1.41 Wed Nov 3 04:32:50 2010
+++ src/sys/miscfs/genfs/genfs_io.c Tue Nov 9 16:31:48 2010
@@ -1,4 +1,4 @@
-/* $NetBSD: genfs_io.c,v 1.41 2010/11/03 04:32:50 uebayasi Exp $ */
+/* $NetBSD: genfs_io.c,v 1.42 2010/11/09 16:31:48 hannken Exp $ */
/*
* Copyright (c) 1982, 1986, 1989, 1993
@@ -31,7 +31,7 @@
*/
#include <sys/cdefs.h>
-__KERNEL_RCSID(0, "$NetBSD: genfs_io.c,v 1.41 2010/11/03 04:32:50 uebayasi Exp $");
+__KERNEL_RCSID(0, "$NetBSD: genfs_io.c,v 1.42 2010/11/09 16:31:48 hannken Exp $");
#include <sys/param.h>
#include <sys/systm.h>
@@ -129,10 +129,11 @@
kauth_cred_t const cred = curlwp->l_cred; /* XXXUBC curlwp */
const bool async = (flags & PGO_SYNCIO) == 0;
const bool memwrite = (ap->a_access_type & VM_PROT_WRITE) != 0;
- bool has_trans = false;
const bool overwrite = (flags & PGO_OVERWRITE) != 0;
const bool blockalloc = memwrite && (flags & PGO_NOBLOCKALLOC) == 0;
const bool glocked = (flags & PGO_GLOCKHELD) != 0;
+ const bool need_wapbl = blockalloc && vp->v_mount->mnt_wapbl;
+ bool has_trans_wapbl = false;
UVMHIST_FUNC("genfs_getpages"); UVMHIST_CALLED(ubchist);
UVMHIST_LOG(ubchist, "vp %p off 0x%x/%x count %d",
@@ -294,9 +295,20 @@
UVMHIST_LOG(ubchist, "ridx %d npages %d startoff %ld endoff %ld",
ridx, npages, startoffset, endoffset);
- if (!has_trans) {
+ if (!has_trans_wapbl) {
fstrans_start(vp->v_mount, FSTRANS_SHARED);
- has_trans = true;
+ /*
+ * XXX: This assumes that we come here only via
+ * the mmio path
+ */
+ if (need_wapbl) {
+ error = WAPBL_BEGIN(vp->v_mount);
+ if (error) {
+ fstrans_done(vp->v_mount);
+ goto out_err_free;
+ }
+ }
+ has_trans_wapbl = true;
}
/*
@@ -621,22 +633,8 @@
*/
if (!error && sawhole && blockalloc) {
- /*
- * XXX: This assumes that we come here only via
- * the mmio path
- */
- if (vp->v_mount->mnt_wapbl) {
- error = WAPBL_BEGIN(vp->v_mount);
- }
-
- if (!error) {
- error = GOP_ALLOC(vp, startoffset,
- npages << PAGE_SHIFT, 0, cred);
- if (vp->v_mount->mnt_wapbl) {
- WAPBL_END(vp->v_mount);
- }
- }
-
+ error = GOP_ALLOC(vp, startoffset,
+ npages << PAGE_SHIFT, 0, cred);
UVMHIST_LOG(ubchist, "gop_alloc off 0x%x/0x%x -> %d",
startoffset, npages << PAGE_SHIFT, error,0);
if (!error) {
@@ -738,8 +736,11 @@
if (pgs != NULL && pgs != pgs_onstack)
kmem_free(pgs, pgs_size);
out_err:
- if (has_trans)
+ if (has_trans_wapbl) {
+ if (need_wapbl)
+ WAPBL_END(vp->v_mount);
fstrans_done(vp->v_mount);
+ }
return error;
}
