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Re: [1/2] RFC: reference count breakpoint commands
- From: Tom Tromey <tromey at redhat dot com>
- To: gdb-patches at sourceware dot org
- Date: Wed, 24 Mar 2010 15:08:27 -0600
- Subject: Re: [1/2] RFC: reference count breakpoint commands
- References: <m36354ltu6.fsf@fleche.redhat.com>
- Reply-to: Tom Tromey <tromey at redhat dot com>
>>>>> "Tom" == Tom Tromey <tromey@redhat.com> writes:
Tom> This adds reference counting for breakpoint commands. This removes a
Tom> longstanding restriction: you can now change a breakpoint's commands
Tom> while the commands are running. This patch also sets the stage for the
Tom> next page.
I am checking this in. I rebased this patch on top of Volodya's recent
commits. The updated patch is appended.
Tom
2010-03-24 Tom Tromey <tromey@redhat.com>
* breakpoint.h (struct counted_command_line): New struct.
(struct breakpoint) <commands>: Change type.
(struct bpstats) <commands>: Change type.
<commands_left>: New field.
* breakpoint.c (alloc_counted_command_line): New function.
(incref_counted_command_line): Likewise.
(decref_counted_command_line): Likewise.
(do_cleanup_counted_command_line): Likewise.
(make_cleanup_decref_counted_command_line): Likewise.
(breakpoint_set_commands): Use decref_counted_command_line and
alloc_counted_command_line.
(commands_command): Don't error if breakpoint commands are
executing.
(commands_from_control_command): Likewise.
(bpstat_free): Update.
(bpstat_copy): Likewise.
(bpstat_clear_actions): Likewise.
(bpstat_do_actions_1): Likewise.
(bpstat_stop_status): Likewise.
(print_one_breakpoint_location): Likewise.
(delete_breakpoint): Likewise.
(bpstat_alloc): Initialize new field.
(tracepoint_save_command): Update.
* tracepoint.c (encode_actions): Update.
(trace_dump_command): Update.
Index: breakpoint.c
===================================================================
RCS file: /cvs/src/src/gdb/breakpoint.c,v
retrieving revision 1.465
diff -u -r1.465 breakpoint.c
--- breakpoint.c 23 Mar 2010 21:36:05 -0000 1.465
+++ breakpoint.c 24 Mar 2010 21:06:51 -0000
@@ -433,6 +433,63 @@
return (b->type == bp_tracepoint || b->type == bp_fast_tracepoint);
}
+/* Allocate a new counted_command_line with reference count of 1.
+ The new structure owns COMMANDS. */
+
+static struct counted_command_line *
+alloc_counted_command_line (struct command_line *commands)
+{
+ struct counted_command_line *result
+ = xmalloc (sizeof (struct counted_command_line));
+ result->refc = 1;
+ result->commands = commands;
+ return result;
+}
+
+/* Increment reference count. This does nothing if CMD is NULL. */
+
+static void
+incref_counted_command_line (struct counted_command_line *cmd)
+{
+ if (cmd)
+ ++cmd->refc;
+}
+
+/* Decrement reference count. If the reference count reaches 0,
+ destroy the counted_command_line. Sets *CMDP to NULL. This does
+ nothing if *CMDP is NULL. */
+
+static void
+decref_counted_command_line (struct counted_command_line **cmdp)
+{
+ if (*cmdp)
+ {
+ if (--(*cmdp)->refc == 0)
+ {
+ free_command_lines (&(*cmdp)->commands);
+ xfree (*cmdp);
+ }
+ *cmdp = NULL;
+ }
+}
+
+/* A cleanup function that calls decref_counted_command_line. */
+
+static void
+do_cleanup_counted_command_line (void *arg)
+{
+ decref_counted_command_line (arg);
+}
+
+/* Create a cleanup that calls decref_counted_command_line on the
+ argument. */
+
+static struct cleanup *
+make_cleanup_decref_counted_command_line (struct counted_command_line **cmdp)
+{
+ return make_cleanup (do_cleanup_counted_command_line, cmdp);
+}
+
/* Default address, symtab and line to put a breakpoint at
for "break" command with no arg.
if default_breakpoint_valid is zero, the other three are
@@ -783,8 +840,8 @@
check_no_tracepoint_commands (commands);
}
- free_command_lines (&b->commands);
- b->commands = commands;
+ decref_counted_command_line (&b->commands);
+ b->commands = alloc_counted_command_line (commands);
breakpoints_changed ();
observer_notify_breakpoint_modified (b->number);
}
@@ -803,13 +860,6 @@
int bnum;
struct command_line *l;
- /* If we allowed this, we would have problems with when to
- free the storage, if we change the commands currently
- being read from. */
-
- if (executing_breakpoint_commands)
- error (_("Can't use the \"commands\" command among a breakpoint's commands."));
-
p = arg;
bnum = get_number (&p);
@@ -847,13 +897,6 @@
char *p;
int bnum;
- /* If we allowed this, we would have problems with when to
- free the storage, if we change the commands currently
- being read from. */
-
- if (executing_breakpoint_commands)
- error (_("Can't use the \"commands\" command among a breakpoint's commands."));
-
/* An empty string for the breakpoint number means the last
breakpoint, but get_number expects a NULL pointer. */
if (arg && !*arg)
@@ -868,12 +911,13 @@
ALL_BREAKPOINTS (b)
if (b->number == bnum)
{
- free_command_lines (&b->commands);
+ decref_counted_command_line (&b->commands);
if (cmd->body_count != 1)
error (_("Invalid \"commands\" block structure."));
/* We need to copy the commands because if/while will free the
list after it finishes execution. */
- b->commands = copy_command_lines (cmd->body_list[0]);
+ b->commands
+ = alloc_counted_command_line (copy_command_lines (cmd->body_list[0]));
breakpoints_changed ();
observer_notify_breakpoint_modified (b->number);
return simple_control;
@@ -2697,7 +2741,7 @@
{
if (bs->old_val != NULL)
value_free (bs->old_val);
- free_command_lines (&bs->commands);
+ decref_counted_command_line (&bs->commands);
xfree (bs);
}
@@ -2739,8 +2783,7 @@
{
tmp = (bpstat) xmalloc (sizeof (*tmp));
memcpy (tmp, bs, sizeof (*tmp));
- if (bs->commands != NULL)
- tmp->commands = copy_command_lines (bs->commands);
+ incref_counted_command_line (tmp->commands);
if (bs->old_val != NULL)
{
tmp->old_val = value_copy (bs->old_val);
@@ -2841,7 +2884,7 @@
{
for (; bs != NULL; bs = bs->next)
{
- free_command_lines (&bs->commands);
+ decref_counted_command_line (&bs->commands);
if (bs->old_val != NULL)
{
value_free (bs->old_val);
@@ -2907,6 +2950,7 @@
breakpoint_proceeded = 0;
for (; bs != NULL; bs = bs->next)
{
+ struct counted_command_line *ccmd;
struct command_line *cmd;
struct cleanup *this_cmd_tree_chain;
@@ -2920,9 +2964,12 @@
commands are only executed once, we don't need to copy it; we
can clear the pointer in the bpstat, and make sure we free
the tree when we're done. */
- cmd = bs->commands;
- bs->commands = 0;
- this_cmd_tree_chain = make_cleanup_free_command_lines (&cmd);
+ ccmd = bs->commands;
+ bs->commands = NULL;
+ this_cmd_tree_chain
+ = make_cleanup_decref_counted_command_line (&ccmd);
+ cmd = bs->commands_left;
+ bs->commands_left = NULL;
while (cmd != NULL)
{
@@ -3305,6 +3352,7 @@
bs->breakpoint_at = bl;
/* If the condition is false, etc., don't do the commands. */
bs->commands = NULL;
+ bs->commands_left = NULL;
bs->old_val = NULL;
bs->print_it = print_it_normal;
return bs;
@@ -3942,15 +3990,17 @@
if (b->silent)
bs->print = 0;
bs->commands = b->commands;
- if (bs->commands
- && (strcmp ("silent", bs->commands->line) == 0
- || (xdb_commands && strcmp ("Q",
- bs->commands->line) == 0)))
+ incref_counted_command_line (bs->commands);
+ bs->commands_left = bs->commands ? bs->commands->commands : NULL;
+ if (bs->commands_left
+ && (strcmp ("silent", bs->commands_left->line) == 0
+ || (xdb_commands
+ && strcmp ("Q",
+ bs->commands_left->line) == 0)))
{
- bs->commands = bs->commands->next;
+ bs->commands_left = bs->commands_left->next;
bs->print = 0;
}
- bs->commands = copy_command_lines (bs->commands);
}
/* Print nothing for this entry if we dont stop or dont print. */
@@ -4617,7 +4667,7 @@
ui_out_text (uiout, " hits\n");
}
- l = b->commands;
+ l = b->commands ? b->commands->commands : NULL;
if (!part_of_multiple && l)
{
struct cleanup *script_chain;
@@ -9021,7 +9071,7 @@
break;
}
- free_command_lines (&bpt->commands);
+ decref_counted_command_line (&bpt->commands);
xfree (bpt->cond_string);
xfree (bpt->cond_exp);
xfree (bpt->addr_string);
@@ -10446,7 +10496,7 @@
ui_out_redirect (uiout, fp);
TRY_CATCH (ex, RETURN_MASK_ERROR)
{
- print_command_lines (uiout, tp->commands, 2);
+ print_command_lines (uiout, tp->commands->commands, 2);
}
ui_out_redirect (uiout, NULL);
Index: breakpoint.h
===================================================================
RCS file: /cvs/src/src/gdb/breakpoint.h,v
retrieving revision 1.110
diff -u -r1.110 breakpoint.h
--- breakpoint.h 23 Mar 2010 21:32:26 -0000 1.110
+++ breakpoint.h 24 Mar 2010 21:06:51 -0000
@@ -376,6 +376,17 @@
typedef struct bp_location *bp_location_p;
DEF_VEC_P(bp_location_p);
+/* A reference-counted struct command_line. This lets multiple
+ breakpoints share a single command list. */
+struct counted_command_line
+{
+ /* The reference count. */
+ int refc;
+
+ /* The command list. */
+ struct command_line *commands;
+};
+
/* Note that the ->silent field is not currently used by any commands
(though the code is in there if it was to be, and set_raw_breakpoint
does set it to 0). I implemented it because I thought it would be
@@ -414,7 +425,7 @@
be continued automatically before really stopping. */
int ignore_count;
/* Chain of command lines to execute when this breakpoint is hit. */
- struct command_line *commands;
+ struct counted_command_line *commands;
/* Stack depth (address of frame). If nonzero, break only if fp
equals this. */
struct frame_id frame_id;
@@ -698,8 +709,11 @@
bpstat next;
/* Breakpoint that we are at. */
const struct bp_location *breakpoint_at;
- /* Commands left to be done. */
- struct command_line *commands;
+ /* The associated command list. */
+ struct counted_command_line *commands;
+ /* Commands left to be done. This points somewhere in
+ base_command. */
+ struct command_line *commands_left;
/* Old value associated with a watchpoint. */
struct value *old_val;
Index: tracepoint.c
===================================================================
RCS file: /cvs/src/src/gdb/tracepoint.c,v
retrieving revision 1.154
diff -u -r1.154 tracepoint.c
--- tracepoint.c 24 Mar 2010 19:37:06 -0000 1.154
+++ tracepoint.c 24 Mar 2010 21:06:55 -0000
@@ -1385,7 +1385,7 @@
gdbarch_virtual_frame_pointer (t->gdbarch,
t->loc->address, &frame_reg, &frame_offset);
- actions = t->commands;
+ actions = t->commands->commands;
/* If there are default expressions to collect, make up a collect
action and prepend to the action list to encode. Note that since
@@ -1406,7 +1406,7 @@
{
default_collect_action = xmalloc (sizeof (struct command_line));
make_cleanup (xfree, default_collect_action);
- default_collect_action->next = t->commands;
+ default_collect_action->next = t->commands->commands;
default_collect_action->line = line;
actions = default_collect_action;
}
@@ -2332,7 +2332,7 @@
if (loc->address == regcache_read_pc (regcache))
stepping_frame = 0;
- for (action = t->commands; action; action = action->next)
+ for (action = t->commands->commands; action; action = action->next)
{
struct cmd_list_element *cmd;