[src/trunk]: src/sys Add percpu_foreach_xcall(), which is like percpu_foreach...

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

details:   https://anonhg.NetBSD.org/src/rev/d5f7fa38faec
branches:  trunk
changeset: 1007117:d5f7fa38faec
user:      thorpej <thorpej%NetBSD.org@localhost>
date:      Fri Feb 07 11:55:22 2020 +0000

description:
Add percpu_foreach_xcall(), which is like percpu_foreach(), except it
runs the callback on the target CPU.

diffstat:

 sys/kern/subr_percpu.c |  51 +++++++++++++++++++++++++++++++++++++++++++++++--
 sys/sys/percpu.h       |   3 +-
 2 files changed, 50 insertions(+), 4 deletions(-)

diffs (93 lines):

diff -r d18b514dd1a0 -r d5f7fa38faec sys/kern/subr_percpu.c
--- a/sys/kern/subr_percpu.c    Fri Feb 07 09:38:29 2020 +0000
+++ b/sys/kern/subr_percpu.c    Fri Feb 07 11:55:22 2020 +0000
@@ -1,4 +1,4 @@
-/*     $NetBSD: subr_percpu.c,v 1.23 2020/02/01 12:53:41 riastradh Exp $       */
+/*     $NetBSD: subr_percpu.c,v 1.24 2020/02/07 11:55:22 thorpej Exp $ */
 
 /*-
  * Copyright (c)2007,2008 YAMAMOTO Takashi,
@@ -31,7 +31,7 @@
  */
 
 #include <sys/cdefs.h>
-__KERNEL_RCSID(0, "$NetBSD: subr_percpu.c,v 1.23 2020/02/01 12:53:41 riastradh Exp $");
+__KERNEL_RCSID(0, "$NetBSD: subr_percpu.c,v 1.24 2020/02/07 11:55:22 thorpej Exp $");
 
 #include <sys/param.h>
 #include <sys/cpu.h>
@@ -412,7 +412,9 @@
 /*
  * percpu_foreach: call the specified callback function for each cpus.
  *
- * => called in thread context.
+ * => must be called from thread context.
+ * => callback executes on **current** CPU (or, really, arbitrary CPU,
+ *    in case of preemption)
  * => caller should not rely on the cpu iteration order.
  * => the callback function should be minimum because it is executed with
  *    holding a global lock, which can block low-priority xcalls.
@@ -430,3 +432,46 @@
        }
        percpu_traverse_exit();
 }
+
+struct percpu_xcall_ctx {
+       percpu_callback_t  ctx_cb;
+       void              *ctx_arg;
+};
+
+static void
+percpu_xcfunc(void * const v1, void * const v2)
+{
+       percpu_t * const pc = v1;
+       struct percpu_xcall_ctx * const ctx = v2;
+
+       (*ctx->ctx_cb)(percpu_getref(pc), ctx->ctx_arg, curcpu());
+       percpu_putref(pc);
+}
+
+/*
+ * percpu_foreach_xcall: call the specified callback function for each
+ * cpu.  This version uses an xcall to run the callback on each cpu.
+ *
+ * => must be called from thread context.
+ * => callback executes on **remote** CPU in soft-interrupt context
+ *    (at the specified soft interrupt priority).
+ * => caller should not rely on the cpu iteration order.
+ * => the callback function should be minimum because it may be
+ *    executed in soft-interrupt context.  eg. it's illegal for
+ *    a callback function to sleep for memory allocation.
+ */
+void
+percpu_foreach_xcall(percpu_t *pc, u_int xcflags, percpu_callback_t cb,
+                    void *arg)
+{
+       struct percpu_xcall_ctx ctx = {
+               .ctx_cb = cb,
+               .ctx_arg = arg,
+       };
+       CPU_INFO_ITERATOR cii;
+       struct cpu_info *ci;
+
+       for (CPU_INFO_FOREACH(cii, ci)) {
+               xc_wait(xc_unicast(xcflags, percpu_xcfunc, pc, &ctx, ci));
+       }
+}
diff -r d18b514dd1a0 -r d5f7fa38faec sys/sys/percpu.h
--- a/sys/sys/percpu.h  Fri Feb 07 09:38:29 2020 +0000
+++ b/sys/sys/percpu.h  Fri Feb 07 11:55:22 2020 +0000
@@ -1,4 +1,4 @@
-/*     $NetBSD: percpu.h,v 1.4 2020/02/01 12:49:02 riastradh Exp $     */
+/*     $NetBSD: percpu.h,v 1.5 2020/02/07 11:55:22 thorpej Exp $       */
 
 /*-
  * Copyright (c)2007,2008 YAMAMOTO Takashi,
@@ -40,6 +40,7 @@
 
 typedef void (*percpu_callback_t)(void *, void *, struct cpu_info *);
 void   percpu_foreach(percpu_t *, percpu_callback_t, void *);
+void   percpu_foreach_xcall(percpu_t *, u_int, percpu_callback_t, void *);
 
 percpu_t *percpu_create(size_t, percpu_callback_t, percpu_callback_t, void *);