Sun Feb 27 14:17:10 2022 UTC ()
alpha: Fix placement of membar for sending ICCB message.

While here, reduce it to membar_exit -- it's obviously not needed for
store-before-load here (although alpha doesn't have anything weaker
than the full sequential consistency `mb'), and although we do need a
store-before-load (and load-before-load) to spin waiting for the CPU
to wake up, that already happens a few lines below with alpha_mb in
the loop anyway.  So no need for membar_sync, which is just `mb'
under the hood -- deleting the membar_sync in this place can't hurt.

The membar_sync had been inserted automatically when converting from
an older style of atomic_ops(3) API.


(riastradh)
diff -r1.104 -r1.105 src/sys/arch/alpha/alpha/cpu.c
cvs diff -r1.104 -r1.105 src/sys/arch/alpha/alpha/cpu.c (expand / switch to unified diff)

--- src/sys/arch/alpha/alpha/cpu.c 2021/05/05 03:54:16 1.104
+++ src/sys/arch/alpha/alpha/cpu.c 2022/02/27 14:17:10 1.105
@@ -1,14 +1,14 @@ @@ -1,14 +1,14 @@
1/* $NetBSD: cpu.c,v 1.104 2021/05/05 03:54:16 thorpej Exp $ */ 1/* $NetBSD: cpu.c,v 1.105 2022/02/27 14:17:10 riastradh Exp $ */
2 2
3/*- 3/*-
4 * Copyright (c) 1998, 1999, 2000, 2001, 2020 The NetBSD Foundation, Inc. 4 * Copyright (c) 1998, 1999, 2000, 2001, 2020 The NetBSD Foundation, Inc.
5 * All rights reserved. 5 * All rights reserved.
6 * 6 *
7 * This code is derived from software contributed to The NetBSD Foundation 7 * This code is derived from software contributed to The NetBSD Foundation
8 * by Jason R. Thorpe of the Numerical Aerospace Simulation Facility, 8 * by Jason R. Thorpe of the Numerical Aerospace Simulation Facility,
9 * NASA Ames Research Center. 9 * NASA Ames Research Center.
10 * 10 *
11 * Redistribution and use in source and binary forms, with or without 11 * Redistribution and use in source and binary forms, with or without
12 * modification, are permitted provided that the following conditions 12 * modification, are permitted provided that the following conditions
13 * are met: 13 * are met:
14 * 1. Redistributions of source code must retain the above copyright 14 * 1. Redistributions of source code must retain the above copyright
@@ -49,27 +49,27 @@ @@ -49,27 +49,27 @@
49 * Carnegie Mellon requests users of this software to return to 49 * Carnegie Mellon requests users of this software to return to
50 * 50 *
51 * Software Distribution Coordinator or Software.Distribution@CS.CMU.EDU 51 * Software Distribution Coordinator or Software.Distribution@CS.CMU.EDU
52 * School of Computer Science 52 * School of Computer Science
53 * Carnegie Mellon University 53 * Carnegie Mellon University
54 * Pittsburgh PA 15213-3890 54 * Pittsburgh PA 15213-3890
55 * 55 *
56 * any improvements or extensions that they make and grant Carnegie the 56 * any improvements or extensions that they make and grant Carnegie the
57 * rights to redistribute these changes. 57 * rights to redistribute these changes.
58 */ 58 */
59 59
60#include <sys/cdefs.h> /* RCS ID & Copyright macro defns */ 60#include <sys/cdefs.h> /* RCS ID & Copyright macro defns */
61 61
62__KERNEL_RCSID(0, "$NetBSD: cpu.c,v 1.104 2021/05/05 03:54:16 thorpej Exp $"); 62__KERNEL_RCSID(0, "$NetBSD: cpu.c,v 1.105 2022/02/27 14:17:10 riastradh Exp $");
63 63
64#include "opt_ddb.h" 64#include "opt_ddb.h"
65#include "opt_multiprocessor.h" 65#include "opt_multiprocessor.h"
66 66
67#include <sys/param.h> 67#include <sys/param.h>
68#include <sys/systm.h> 68#include <sys/systm.h>
69#include <sys/device.h> 69#include <sys/device.h>
70#include <sys/kmem.h> 70#include <sys/kmem.h>
71#include <sys/proc.h> 71#include <sys/proc.h>
72#include <sys/atomic.h> 72#include <sys/atomic.h>
73#include <sys/cpu.h> 73#include <sys/cpu.h>
74#include <sys/sysctl.h> 74#include <sys/sysctl.h>
75 75
@@ -872,32 +872,33 @@ cpu_iccb_send(long cpu_id, const char *m @@ -872,32 +872,33 @@ cpu_iccb_send(long cpu_id, const char *m
872 872
873 /* Wait for the ICCB to become available. */ 873 /* Wait for the ICCB to become available. */
874 for (timeout = 10000; timeout != 0; timeout--) { 874 for (timeout = 10000; timeout != 0; timeout--) {
875 alpha_mb(); 875 alpha_mb();
876 if ((hwrpb->rpb_rxrdy & cpumask) == 0) 876 if ((hwrpb->rpb_rxrdy & cpumask) == 0)
877 break; 877 break;
878 delay(1000); 878 delay(1000);
879 } 879 }
880 if (timeout == 0) 880 if (timeout == 0)
881 return (EIO); 881 return (EIO);
882 882
883 /* 883 /*
884 * Copy the message into the ICCB, and tell the secondary console 884 * Copy the message into the ICCB, and tell the secondary console
885 * that it's there. 885 * that it's there. Ensure the buffer is initialized before we
 886 * set the rxrdy bits, as a store-release.
886 */ 887 */
887 strcpy(pcsp->pcs_iccb.iccb_rxbuf, msg); 888 strcpy(pcsp->pcs_iccb.iccb_rxbuf, msg);
888 pcsp->pcs_iccb.iccb_rxlen = strlen(msg); 889 pcsp->pcs_iccb.iccb_rxlen = strlen(msg);
 890 membar_exit();
889 atomic_or_ulong(&hwrpb->rpb_rxrdy, cpumask); 891 atomic_or_ulong(&hwrpb->rpb_rxrdy, cpumask);
890 membar_sync(); 
891 892
892 /* Wait for the message to be received. */ 893 /* Wait for the message to be received. */
893 for (timeout = 10000; timeout != 0; timeout--) { 894 for (timeout = 10000; timeout != 0; timeout--) {
894 alpha_mb(); 895 alpha_mb();
895 if ((hwrpb->rpb_rxrdy & cpumask) == 0) 896 if ((hwrpb->rpb_rxrdy & cpumask) == 0)
896 break; 897 break;
897 delay(1000); 898 delay(1000);
898 } 899 }
899 if (timeout == 0) 900 if (timeout == 0)
900 return (EIO); 901 return (EIO);
901 902
902 return (0); 903 return (0);
903} 904}