[src/trunk]: src/sys/arch/alpha/alpha - alpha_ipi_process(): Continue process...

[thorpej <thorpej%NetBSD.org@localhost>]

details:   https://anonhg.NetBSD.org/src/rev/73edb0b94374
branches:  trunk
changeset: 943420:73edb0b94374
user:      thorpej <thorpej%NetBSD.org@localhost>
date:      Thu Sep 03 02:03:14 2020 +0000

description:
- alpha_ipi_process(): Continue processing IPIs until the ipimask
  reads 0.  Issue a memory barrier between the atomic swap and performing
  the work.
- alpha_send_ipi(): Issue a memory barrier before setting the ipimask
  to ensure all memory accesses prior to signalling the IPI have
  completed.  Also issue a memory barrier getween setting the ipimask
  and calling PALcode to write the IPIR.

diffstat:

 sys/arch/alpha/alpha/ipifuncs.c |  47 +++++++++++++++++++++++++++-------------
 1 files changed, 31 insertions(+), 16 deletions(-)

diffs (78 lines):

diff -r c04e5cfc3eba -r 73edb0b94374 sys/arch/alpha/alpha/ipifuncs.c
--- a/sys/arch/alpha/alpha/ipifuncs.c   Thu Sep 03 00:23:57 2020 +0000
+++ b/sys/arch/alpha/alpha/ipifuncs.c   Thu Sep 03 02:03:14 2020 +0000
@@ -1,4 +1,4 @@
-/* $NetBSD: ipifuncs.c,v 1.52 2020/08/29 20:06:59 thorpej Exp $ */
+/* $NetBSD: ipifuncs.c,v 1.53 2020/09/03 02:03:14 thorpej Exp $ */
 
 /*-
  * Copyright (c) 1998, 1999, 2000, 2001 The NetBSD Foundation, Inc.
@@ -32,7 +32,7 @@
 
 #include <sys/cdefs.h>                 /* RCS ID & Copyright macro defns */
 
-__KERNEL_RCSID(0, "$NetBSD: ipifuncs.c,v 1.52 2020/08/29 20:06:59 thorpej Exp $");
+__KERNEL_RCSID(0, "$NetBSD: ipifuncs.c,v 1.53 2020/09/03 02:03:14 thorpej Exp $");
 
 /*
  * Interprocessor interrupt handlers.
@@ -125,22 +125,20 @@
        }
 #endif
 
-       pending_ipis = atomic_swap_ulong(&ci->ci_ipis, 0);
+       while ((pending_ipis = atomic_swap_ulong(&ci->ci_ipis, 0)) != 0) {
+               /*
+                * Ensure the atomic swap is globally visible before
+                * we do any of the work.
+                */
+               membar_enter();
 
-       /*
-        * For various reasons, it is possible to have spurious calls
-        * to this routine, so just bail out now if there are none
-        * pending.
-        */
-       if (pending_ipis == 0)
-               return;
+               sc->sc_evcnt_ipi.ev_count++;
 
-       sc->sc_evcnt_ipi.ev_count++;
-
-       for (bit = 0; bit < ALPHA_NIPIS; bit++) {
-               if (pending_ipis & (1UL << bit)) {
-                       sc->sc_evcnt_which_ipi[bit].ev_count++;
-                       (*ipifuncs[bit])(ci, framep);
+               for (bit = 0; bit < ALPHA_NIPIS; bit++) {
+                       if (pending_ipis & (1UL << bit)) {
+                               sc->sc_evcnt_which_ipi[bit].ev_count++;
+                               (*ipifuncs[bit])(ci, framep);
+                       }
                }
        }
 }
@@ -156,7 +154,24 @@
        KASSERT(cpu_info[cpu_id] != NULL);
        KASSERT(cpus_running & (1UL << cpu_id));
 
+       /*
+        * Make sure all loads and stores prior to calling
+        * alpha_send_ipi() have completed before informing
+        * the CPU of the work we are asking it to do.
+        */
+       membar_exit();
        atomic_or_ulong(&cpu_info[cpu_id]->ci_ipis, ipimask);
+
+       /*
+        * Ensure that the store of ipimask completes before actually
+        * writing to the IPIR.
+        *
+        * Note: we use MB rather than WMB because how the IPIR
+        * is implemented is not architecturally specified, and
+        * WMB is only guaranteed to provide ordering for stores
+        * to regions of the same memory-likeness.
+        */
+       alpha_mb();
        alpha_pal_wripir(cpu_id);
 }