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); }