The 'ftdump' command in kdb is currently a bit of a last resort, at
least if you have lots of traces turned on. It's going to print a
whole boatload of lines out your serial port which is probably running
at 115200. This could easily take many, many minutes.
Usually you're most interested in what's at the _end_ of the ftrace
buffer, AKA what happened most recently. That means you've got to
wait the full time for the dump. The 'ftdump' command does attempt to
help you a little bit by allowing you to skip a fixed number of lines.
Unfortunately it provides no way for you to know how many lines you
should skip.
Let's do similar to python and allow you to use a negative number to
indicate that you want to skip all lines except the last few. This
allows you to quickly see what you want.
Signed-off-by: Douglas Anderson <diand...@chromium.org>
---
kernel/trace/trace_kdb.c | 51 ++++++++++++++++++++++++++--------------
1 file changed, 34 insertions(+), 17 deletions(-)
diff --git a/kernel/trace/trace_kdb.c b/kernel/trace/trace_kdb.c
index be84fa1ded35..40844e168a8c 100644
--- a/kernel/trace/trace_kdb.c
+++ b/kernel/trace/trace_kdb.c
@@ -17,7 +17,7 @@
#include "trace.h"
#include "trace_output.h"
-static void ftrace_dump_buf(int skip_lines, long cpu_file)
+static int ftrace_dump_buf(int skip_lines, long cpu_file, bool quiet)
{
/* use static because iter can be a bit big for the stack */
static struct trace_iterator iter;
@@ -39,7 +39,9 @@ static void ftrace_dump_buf(int skip_lines, long cpu_file)
/* don't look at user memory in panic mode */
tr->trace_flags &= ~TRACE_ITER_SYM_USEROBJ;
- kdb_printf("Dumping ftrace buffer:\n");
+ if (!quiet)
+ kdb_printf("Dumping ftrace buffer (skipping %d lines):\n",
+ skip_lines);
/* reset all but tr, trace, and overruns */
memset(&iter.seq, 0,
@@ -66,25 +68,29 @@ static void ftrace_dump_buf(int skip_lines, long cpu_file)
}
while (trace_find_next_entry_inc(&iter)) {
- if (!cnt)
- kdb_printf("---------------------------------\n");
- cnt++;
-
- if (!skip_lines) {
- print_trace_line(&iter);
- trace_printk_seq(&iter.seq);
- } else {
- skip_lines--;
+ if (!quiet) {
+ if (!cnt)
+
kdb_printf("---------------------------------\n");
+
+ if (!skip_lines) {
+ print_trace_line(&iter);
+ trace_printk_seq(&iter.seq);
+ } else {
+ skip_lines--;
+ }
}
+ cnt++;
if (KDB_FLAG(CMD_INTERRUPT))
goto out;
}
- if (!cnt)
- kdb_printf(" (ftrace buffer empty)\n");
- else
- kdb_printf("---------------------------------\n");
+ if (!quiet) {
+ if (!cnt)
+ kdb_printf(" (ftrace buffer empty)\n");
+ else
+ kdb_printf("---------------------------------\n");
+ }
out:
tr->trace_flags = old_userobj;
@@ -99,6 +105,8 @@ static void ftrace_dump_buf(int skip_lines, long cpu_file)
iter.buffer_iter[cpu] = NULL;
}
}
+
+ return cnt;
}
/*
@@ -109,6 +117,7 @@ static int kdb_ftdump(int argc, const char **argv)
int skip_lines = 0;
long cpu_file;
char *cp;
+ int count;
if (argc > 2)
return KDB_ARGCOUNT;
@@ -129,7 +138,14 @@ static int kdb_ftdump(int argc, const char **argv)
}
kdb_trap_printk++;
- ftrace_dump_buf(skip_lines, cpu_file);
+
+ /* A negative skip_lines means skip all but the last lines */
+ if (skip_lines < 0) {
+ count = ftrace_dump_buf(0, cpu_file, true);
+ skip_lines = max(count + skip_lines, 0);
+ }
+
+ count = ftrace_dump_buf(skip_lines, cpu_file, false);
kdb_trap_printk--;
return 0;
@@ -138,7 +154,8 @@ static int kdb_ftdump(int argc, const char **argv)
static __init int kdb_ftrace_register(void)
{
kdb_register_flags("ftdump", kdb_ftdump, "[skip_#lines] [cpu]",
- "Dump ftrace log", 0, KDB_ENABLE_ALWAYS_SAFE);
+ "Dump ftrace log; -skip dumps last #lines", 0,
+ KDB_ENABLE_ALWAYS_SAFE);
return 0;
}
--
2.21.0.352.gf09ad66450-goog
