Module Name: src
Committed By: maxv
Date: Mon Nov 11 09:50:11 UTC 2019
Modified Files:
src/sys/kern: subr_xcall.c
Log Message:
Remove lockless reads of 'xc_donep'. This is an uint64_t, and we cannot
expect the accesses to be MP-safe on 32bit arches.
Found by KCSAN.
To generate a diff of this commit:
cvs rdiff -u -r1.27 -r1.28 src/sys/kern/subr_xcall.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/kern/subr_xcall.c
diff -u src/sys/kern/subr_xcall.c:1.27 src/sys/kern/subr_xcall.c:1.28
--- src/sys/kern/subr_xcall.c:1.27 Sun Oct 6 15:11:17 2019
+++ src/sys/kern/subr_xcall.c Mon Nov 11 09:50:11 2019
@@ -1,4 +1,4 @@
-/* $NetBSD: subr_xcall.c,v 1.27 2019/10/06 15:11:17 uwe Exp $ */
+/* $NetBSD: subr_xcall.c,v 1.28 2019/11/11 09:50:11 maxv Exp $ */
/*-
* Copyright (c) 2007-2010 The NetBSD Foundation, Inc.
@@ -74,7 +74,7 @@
*/
#include <sys/cdefs.h>
-__KERNEL_RCSID(0, "$NetBSD: subr_xcall.c,v 1.27 2019/10/06 15:11:17 uwe Exp $");
+__KERNEL_RCSID(0, "$NetBSD: subr_xcall.c,v 1.28 2019/11/11 09:50:11 maxv Exp $");
#include <sys/types.h>
#include <sys/param.h>
@@ -334,12 +334,7 @@ xc_wait(uint64_t where)
xc = &xc_low_pri;
}
- /* Fast path, if already done. */
- if (xc->xc_donep >= where) {
- return;
- }
-
- /* Slow path: block until awoken. */
+ /* Block until awoken. */
mutex_enter(&xc->xc_lock);
while (xc->xc_donep < where) {
cv_wait(&xc->xc_busy, &xc->xc_lock);
@@ -462,7 +457,6 @@ xc__highpri_intr(void *dummy)
* Lock-less fetch of function and its arguments.
* Safe since it cannot change at this point.
*/
- KASSERT(xc->xc_donep < xc->xc_headp);
func = xc->xc_func;
arg1 = xc->xc_arg1;
arg2 = xc->xc_arg2;
@@ -475,6 +469,7 @@ xc__highpri_intr(void *dummy)
* cross-call has been processed - notify waiters, if any.
*/
mutex_enter(&xc->xc_lock);
+ KASSERT(xc->xc_donep < xc->xc_headp);
if (++xc->xc_donep == xc->xc_headp) {
cv_broadcast(&xc->xc_busy);
}
