Module Name: src
Committed By: riastradh
Date: Wed Mar 1 08:18:04 UTC 2023
Modified Files:
src/sys/arch/mips/mips: locore.S
Log Message:
mips: Optimization: Omit needless membar when triggering softint.
When we are triggering a softint, it can't already hold any mutexes.
So any path to mutex_exit(mtx) must go via mutex_enter(mtx), which is
always done with atomic r/m/w, and we need not issue any explicit
barrier between ci->ci_curlwp = softlwp and a potential load of
mtx->mtx_owner in mutex_exit.
PR kern/57240
XXX pullup-8
XXX pullup-9
XXX pullup-10
To generate a diff of this commit:
cvs rdiff -u -r1.229 -r1.230 src/sys/arch/mips/mips/locore.S
Please note that diffs are not public domain; they are subject to the
copyright notices on the relevant files.
Modified files:
Index: src/sys/arch/mips/mips/locore.S
diff -u src/sys/arch/mips/mips/locore.S:1.229 src/sys/arch/mips/mips/locore.S:1.230
--- src/sys/arch/mips/mips/locore.S:1.229 Thu Feb 23 14:56:00 2023
+++ src/sys/arch/mips/mips/locore.S Wed Mar 1 08:18:03 2023
@@ -1,4 +1,4 @@
-/* $NetBSD: locore.S,v 1.229 2023/02/23 14:56:00 riastradh Exp $ */
+/* $NetBSD: locore.S,v 1.230 2023/03/01 08:18:03 riastradh Exp $ */
/*
* Copyright (c) 1992, 1993
@@ -63,7 +63,7 @@
#include <mips/trap.h>
#include <mips/locore.h>
-RCSID("$NetBSD: locore.S,v 1.229 2023/02/23 14:56:00 riastradh Exp $")
+RCSID("$NetBSD: locore.S,v 1.230 2023/03/01 08:18:03 riastradh Exp $")
#include "assym.h"
@@ -429,7 +429,13 @@ NESTED(softint_fast_dispatch, CALLFRAME_
nop # patchable load delay slot
SYNC_PRODUCER /* XXX fixup */ /* for mutex_enter; see cpu_switchto */
PTR_S MIPS_CURLWP, CPU_INFO_CURLWP(s1) # ...
- SYNC_DEKKER /* XXX fixup */ /* for mutex_enter; see cpu_switchto */
+ /*
+ * No need for barrier after ci->ci_curlwp = softlwp -- when we
+ * enter a softint lwp, it can't be holding any mutexes, so it
+ * can't release any until after it has acquired them, so we
+ * need not participate in the protocol with mutex_vector_enter
+ * barriers here.
+ */
move s2, sp # remember sp
move s3, t0 # remember curpcb
