[patch] thread info - automatic skip frames

Jim Houston
2004-03-08T18:23:49Z

Hi Everyone,

I developed this patch to support using kgdb on the
x86-64 linux kernel.

The patch adds an option to gdb to skip over boring frames
in the "thread info" results. This is useful when most of
the threads are stopped in the context switch code. It lets
you see the frame which shows why the the thread blocked.

Use:
set skip-frame thread_return,schedule_timeout

Jim Houston - Concurrent Computer Corp.

--

--- old/gdb-6.0/gdb/thread.c 2004-01-06 12:34:14.786496352 -0500
+++ new/gdb-6.0/gdb/thread.c 2004-01-06 12:34:28.804365312 -0500
@@ -404,6 +404,43 @@
}
}

+/*
+ * When using gdb as a kernel debugger, its really boring to
+ * see every thread is blocked in schedule. By setting a
+ * list of functions with "set skip-frame schedule,thread_return"
+ * we can display the frame that called into the scheduler.
+ */
+static char *skip_frame_string;
+
+int
+skip_frame(struct frame_info *fi)
+{
+ struct minimal_symbol *msym;
+ CORE_ADDR pc;
+ char *name;
+ char *s, *r;
+ int n;
+
+ pc = get_frame_pc (fi);
+ msym = lookup_minimal_symbol_by_pc_section(pc, NULL);
+ if (!msym)
+ return 0;
+ name = SYMBOL_LINKAGE_NAME(msym);
+
+ for (s = skip_frame_string; s && *s ; ) {
+ if ((r = strchr(s, ',')))
+ n = r - s - 1;
+ else
+ n = strlen(s);
+ if (n && strncmp(s, name, n) == 0)
+ return 1;
+ if (!r)
+ break;
+ s = r + 1;
+ }
+ return 0;
+}
+
/* Print information about currently known threads

* Note: this has the drawback that it _really_ switches
@@ -416,7 +453,7 @@
{
struct thread_info *tp;
ptid_t current_ptid;
- struct frame_info *cur_frame;
+ struct frame_info *cur_frame, *fi;
int saved_frame_level = frame_relative_level (get_selected_frame ());
int counter;
char *extra_info;
@@ -448,6 +485,18 @@
puts_filtered (" ");

switch_to_thread (tp->ptid);
+
+ if (skip_frame_string) {
+ /* skip up the stack to an interesting frame. */
+ fi = get_selected_frame ();
+ while (fi) {
+ if (!skip_frame(fi))
+ break;
+ fi = get_prev_frame(fi);
+ if (fi)
+ select_frame(fi);
+ }
+ }
print_stack_frame (get_selected_frame (), -1, 0);
}

@@ -740,4 +789,12 @@

if (!xdb_commands)
add_com_alias ("t", "thread", class_run, 1);
+
+ add_show_from_set (add_set_cmd ("skip-frame", class_obscure,
+ var_string_noescape, (char *)&skip_frame_string, "\
+Set list of functions to skip when choosing the frame to display\n\
+for a info-thread command. When gdb is used for kernel debug this option\n\
+allows the frame which calls the scheduler to be displayed rather than\n\
+having all blocked threads showing the same function in the scheduler.",
+ &setlist), &showlist);
}