Mon Jul 20 16:43:03 2020 UTC ()

Fix fpu_kern_enter in a softint that interrupted a softint.

We need to find the lwp that was originally interrupted to save its
fpu state.

With this, fpu-heavy programs (like firefox) are once again stable,
at least under modest stress testing, on systems configured to use
wifi with WPA2 and CCMP.


(riastradh)

diff -r1.71 -r1.72 src/sys/arch/x86/x86/fpu.c

--- src/sys/arch/x86/x86/fpu.c 2020/07/20 16:41:18	1.71
+++ src/sys/arch/x86/x86/fpu.c 2020/07/20 16:43:03	1.72

 @@ -1,14 +1,14 @@
-/*	$NetBSD: fpu.c,v 1.71 2020/07/20 16:41:18 riastradh Exp $	*/
+/*	$NetBSD: fpu.c,v 1.72 2020/07/20 16:43:03 riastradh Exp $	*/
 /*
  * Copyright (c) 2008, 2019 The NetBSD Foundation, Inc.  All
  * rights reserved.
+ *
  * This code is derived from software developed for The NetBSD Foundation
  * by Andrew Doran and Maxime Villard.
+ *
  * Redistribution and use in source and binary forms, with or without
  * modification, are permitted provided that the following conditions
  * are met:
  * 1. Redistributions of source code must retain the above copyright
  *    notice, this list of conditions and the following disclaimer.
 @@ -86,27 +86,27 @@
  * ARE DISCLAIMED.  IN NO EVENT SHALL THE REGENTS OR CONTRIBUTORS BE LIABLE
  * FOR ANY DIRECT, INDIRECT, INCIDENTAL, SPECIAL, EXEMPLARY, OR CONSEQUENTIAL
  * DAMAGES (INCLUDING, BUT NOT LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS
  * OR SERVICES; LOSS OF USE, DATA, OR PROFITS; OR BUSINESS INTERRUPTION)
  * HOWEVER CAUSED AND ON ANY THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT
  * LIABILITY, OR TORT (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY
  * OUT OF THE USE OF THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF
  * SUCH DAMAGE.
+ *
  *	@(#)npx.c	7.2 (Berkeley) 5/12/91
  */
 #include <sys/cdefs.h>
-__KERNEL_RCSID(0, "$NetBSD: fpu.c,v 1.71 2020/07/20 16:41:18 riastradh Exp $");
+__KERNEL_RCSID(0, "$NetBSD: fpu.c,v 1.72 2020/07/20 16:43:03 riastradh Exp $");
 #include "opt_multiprocessor.h"
 #include <sys/param.h>
 #include <sys/systm.h>
 #include <sys/conf.h>
 #include <sys/cpu.h>
 #include <sys/file.h>
 #include <sys/proc.h>
 #include <sys/kernel.h>
 #include <sys/sysctl.h>
 #include <sys/xcall.h>
 @@ -370,31 +370,29 @@ fpu_kern_enter(void)
 	int s;
 	s = splvm();
 	ci = curcpu();
 	KASSERTMSG(ci->ci_ilevel <= IPL_VM, "ilevel=%d", ci->ci_ilevel);
 	KASSERT(ci->ci_kfpu_spl == -1);
 	ci->ci_kfpu_spl = s;
 	/*
 	 * If we are in a softint and have a pinned lwp, the fpu state is that
 	 * of the pinned lwp, so save it there.
 	 */
-	if ((l->l_pflag & LP_INTR) && (l->l_switchto != NULL)) {
+	while ((l->l_pflag & LP_INTR) && (l->l_switchto != NULL))
-		fpu_save_lwp(l->l_switchto);
+		l = l->l_switchto;
-	} else {
+	fpu_save_lwp(l);
 		fpu_save_lwp(l);
 	/*
 	 * Clear CR0_TS, which fpu_save_lwp set if it saved anything --
 	 * otherwise the CPU will trap if we try to use the FPU under
 	 * the false impression that there has been a task switch since
 	 * the last FPU usage requiring that we save the FPU state.
 	 */
 	clts();
+}
 /*
  * fpu_kern_leave()
+ *