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[1/2] RFC: reference count breakpoint commands
- From: Tom Tromey <tromey at redhat dot com>
- To: gdb-patches at sourceware dot org
- Date: Tue, 09 Mar 2010 20:49:05 -0700
- Subject: [1/2] RFC: reference count breakpoint commands
- Reply-to: tromey at redhat dot com
I'd appreciate comments on this. Barring comments I will commit it
soonish.
This adds reference counting for breakpoint commands. This removes a
longstanding restriction: you can now change a breakpoint's commands
while the commands are running. This patch also sets the stage for the
next page.
Built and regtested on x86-64 (compile farm).
Tom
2010-03-09 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.
diff --git a/gdb/breakpoint.c b/gdb/breakpoint.c
index bd3330f..e817a23 100644
--- a/gdb/breakpoint.c
+++ b/gdb/breakpoint.c
@@ -431,6 +431,63 @@ tracepoint_type (const struct breakpoint *b)
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
@@ -684,8 +741,8 @@ condition_command (char *arg, int from_tty)
void
breakpoint_set_commands (struct breakpoint *b, struct command_line *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);
}
@@ -698,13 +755,6 @@ commands_command (char *arg, int from_tty)
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);
@@ -737,13 +787,6 @@ commands_from_control_command (char *arg, struct command_line *cmd)
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)
@@ -758,12 +801,13 @@ commands_from_control_command (char *arg, struct command_line *cmd)
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;
@@ -2553,7 +2597,7 @@ bpstat_free (bpstat bs)
{
if (bs->old_val != NULL)
value_free (bs->old_val);
- free_command_lines (&bs->commands);
+ decref_counted_command_line (&bs->commands);
xfree (bs);
}
@@ -2595,8 +2639,7 @@ bpstat_copy (bpstat bs)
{
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);
@@ -2697,7 +2740,7 @@ bpstat_clear_actions (bpstat bs)
{
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);
@@ -2763,6 +2806,7 @@ bpstat_do_actions_1 (bpstat *bsp)
breakpoint_proceeded = 0;
for (; bs != NULL; bs = bs->next)
{
+ struct counted_command_line *ccmd;
struct command_line *cmd;
struct cleanup *this_cmd_tree_chain;
@@ -2776,9 +2820,12 @@ bpstat_do_actions_1 (bpstat *bsp)
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)
{
@@ -3161,6 +3208,7 @@ bpstat_alloc (const struct bp_location *bl, bpstat cbs /* Current "bs" value */
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;
@@ -3747,15 +3795,17 @@ bpstat_stop_status (struct address_space *aspace,
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. */
@@ -4422,7 +4472,7 @@ print_one_breakpoint_location (struct breakpoint *b,
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;
@@ -8841,7 +8891,7 @@ delete_breakpoint (struct breakpoint *bpt)
break;
}
- free_command_lines (&bpt->commands);
+ decref_counted_command_line (&bpt->commands);
if (bpt->cond_string != NULL)
xfree (bpt->cond_string);
if (bpt->addr_string != NULL)
diff --git a/gdb/breakpoint.h b/gdb/breakpoint.h
index 6b373a3..1480991 100644
--- a/gdb/breakpoint.h
+++ b/gdb/breakpoint.h
@@ -374,6 +374,17 @@ DEF_VEC_I(int);
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
@@ -412,7 +423,7 @@ struct breakpoint
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;
@@ -694,8 +705,11 @@ struct bpstats
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;