[src/trunk]: src/sys/kern Stop allocating buffers dynamically in a DDB sessio...

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

details:   https://anonhg.NetBSD.org/src/rev/12e110b5e86b
branches:  trunk
changeset: 933949:12e110b5e86b
user:      rin <rin%NetBSD.org@localhost>
date:      Sun May 31 23:24:20 2020 +0000

description:
Stop allocating buffers dynamically in a DDB session, in order not to
disturb on-going debugged state of kernel datastructures.

Since DDB is running on 1 CPU at a time, static buffers are enough.

Increase in BSS section is:
  52552 for amd64 (LP64)
   9152 for m68k  (ILP32)

Requested by thorpej@ and mrg@.
Also suggested by ryo@.
Thanks!

diffstat:

 sys/kern/kern_timeout.c |  46 ++++++++++++++++------------------------------
 1 files changed, 16 insertions(+), 30 deletions(-)

diffs (93 lines):

diff -r 35c7c9551f5b -r 12e110b5e86b sys/kern/kern_timeout.c
--- a/sys/kern/kern_timeout.c   Sun May 31 18:33:08 2020 +0000
+++ b/sys/kern/kern_timeout.c   Sun May 31 23:24:20 2020 +0000
@@ -1,4 +1,4 @@
-/*     $NetBSD: kern_timeout.c,v 1.63 2020/05/31 09:59:37 rin Exp $    */
+/*     $NetBSD: kern_timeout.c,v 1.64 2020/05/31 23:24:20 rin Exp $    */
 
 /*-
  * Copyright (c) 2003, 2006, 2007, 2008, 2009, 2019 The NetBSD Foundation, Inc.
@@ -59,7 +59,7 @@
  */
 
 #include <sys/cdefs.h>
-__KERNEL_RCSID(0, "$NetBSD: kern_timeout.c,v 1.63 2020/05/31 09:59:37 rin Exp $");
+__KERNEL_RCSID(0, "$NetBSD: kern_timeout.c,v 1.64 2020/05/31 23:24:20 rin Exp $");
 
 /*
  * Timeouts are kept in a hierarchical timing wheel.  The c_time is the
@@ -102,9 +102,11 @@
 #include <ddb/db_interface.h>
 #include <ddb/db_access.h>
 #include <ddb/db_cpu.h>
-#include <ddb/db_command.h>
 #include <ddb/db_sym.h>
 #include <ddb/db_output.h>
+
+static struct callout_cpu ccb;
+static struct cpu_info cib;
 #endif
 
 #define BUCKETS                1024
@@ -835,9 +837,8 @@
 void
 db_show_callout(db_expr_t addr, bool haddr, db_expr_t count, const char *modif)
 {
-       struct callout_cpu *cc, *ccp;
-       struct cpu_info *ci, *cip;
-       const size_t ccs = sizeof(*cc), cis = sizeof(*ci);
+       struct callout_cpu *cc;
+       struct cpu_info *ci;
        int b;
 
 #ifndef CRASH
@@ -845,40 +846,25 @@
 #endif
        db_printf("    ticks  wheel               arg  func\n");
 
-       ccp = db_alloc(ccs);
-       if (ccp == NULL) {
-               db_printf("%s: cannot allocate callout_cpu\n", __func__);
-               return;
-       }
-       cip = db_alloc(cis);
-       if (cip == NULL) {
-               db_free(ccp, ccs);
-               db_printf("%s: cannot allocate cpu_info\n", __func__);
-               return;
-       }
-
        /*
         * Don't lock the callwheel; all the other CPUs are paused
         * anyhow, and we might be called in a circumstance where
         * some other CPU was paused while holding the lock.
         */
        for (ci = db_cpu_first(); ci != NULL; ci = db_cpu_next(ci)) {
-               db_read_bytes((db_addr_t)ci, cis, (char *)cip);
-               cc = cip->ci_data.cpu_callout;
-               db_read_bytes((db_addr_t)cc, ccs, (char *)ccp);
-               db_show_callout_bucket(ccp, &cc->cc_todo, &ccp->cc_todo);
+               db_read_bytes((db_addr_t)ci, sizeof(cib), (char *)&cib);
+               cc = cib.ci_data.cpu_callout;
+               db_read_bytes((db_addr_t)cc, sizeof(ccb), (char *)&ccb);
+               db_show_callout_bucket(&ccb, &cc->cc_todo, &ccb.cc_todo);
        }
        for (b = 0; b < BUCKETS; b++) {
                for (ci = db_cpu_first(); ci != NULL; ci = db_cpu_next(ci)) {
-                       db_read_bytes((db_addr_t)ci, cis, (char *)cip);
-                       cc = cip->ci_data.cpu_callout;
-                       db_read_bytes((db_addr_t)cc, ccs, (char *)ccp);
-                       db_show_callout_bucket(ccp, &cc->cc_wheel[b],
-                           &ccp->cc_wheel[b]);
+                       db_read_bytes((db_addr_t)ci, sizeof(cib), (char *)&cib);
+                       cc = cib.ci_data.cpu_callout;
+                       db_read_bytes((db_addr_t)cc, sizeof(ccb), (char *)&ccb);
+                       db_show_callout_bucket(&ccb, &cc->cc_wheel[b],
+                           &ccb.cc_wheel[b]);
                }
        }
-
-       db_free(ccp, ccs);
-       db_free(cip, cis);
 }
 #endif /* DDB */