ftrace,kdb: Allow dumping a specific cpu's buffer with ftdump

In systems with more than one processor it is desirable to look at the
per cpu trace buffers.

Signed-off-by: Jason Wessel <jason.wessel@windriver.com>
Acked-by: Steven Rostedt <rostedt@goodmis.org>
CC: Frederic Weisbecker <fweisbec@gmail.com>

diff --git a/kernel/trace/trace_kdb.c b/kernel/trace/trace_kdb.c
index 44cbda25b0a5b9845adfc8cb8e9888722f971401..7b8ecd751d9395b4d07d22f347bf51dea457ffad 100644 (file)
--- 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)
+static void ftrace_dump_buf(int skip_lines, long cpu_file)
 {
        /* use static because iter can be a bit big for the stack */
        static struct trace_iterator iter;
@@ -44,13 +44,20 @@ static void ftrace_dump_buf(int skip_lines)
        iter.iter_flags |= TRACE_FILE_LAT_FMT;
        iter.pos = -1;
 
-       for_each_tracing_cpu(cpu) {
-               iter.buffer_iter[cpu] =
+       if (cpu_file == TRACE_PIPE_ALL_CPU) {
+               for_each_tracing_cpu(cpu) {
+                       iter.buffer_iter[cpu] =
                        ring_buffer_read_prepare(iter.tr->buffer, cpu);
-               ring_buffer_read_start(iter.buffer_iter[cpu]);
-               tracing_iter_reset(&iter, cpu);
+                       ring_buffer_read_start(iter.buffer_iter[cpu]);
+                       tracing_iter_reset(&iter, cpu);
+               }
+       } else {
+               iter.cpu_file = cpu_file;
+               iter.buffer_iter[cpu_file] =
+                       ring_buffer_read_prepare(iter.tr->buffer, cpu_file);
+               ring_buffer_read_start(iter.buffer_iter[cpu_file]);
+               tracing_iter_reset(&iter, cpu_file);
        }
-
        if (!trace_empty(&iter))
                trace_find_next_entry_inc(&iter);
        while (!trace_empty(&iter)) {
@@ -91,9 +98,10 @@ out:
 static int kdb_ftdump(int argc, const char **argv)
 {
        int skip_lines = 0;
+       long cpu_file;
        char *cp;
 
-       if (argc > 1)
+       if (argc > 2)
                return KDB_ARGCOUNT;
 
        if (argc) {
@@ -102,8 +110,17 @@ static int kdb_ftdump(int argc, const char **argv)
                        skip_lines = 0;
        }
 
+       if (argc == 2) {
+               cpu_file = simple_strtol(argv[2], &cp, 0);
+               if (*cp || cpu_file >= NR_CPUS || cpu_file < 0 ||
+                   !cpu_online(cpu_file))
+                       return KDB_BADINT;
+       } else {
+               cpu_file = TRACE_PIPE_ALL_CPU;
+       }
+
        kdb_trap_printk++;
-       ftrace_dump_buf(skip_lines);
+       ftrace_dump_buf(skip_lines, cpu_file);
        kdb_trap_printk--;
 
        return 0;
@@ -111,8 +128,8 @@ static int kdb_ftdump(int argc, const char **argv)
 
 static __init int kdb_ftrace_register(void)
 {
-       kdb_register_repeat("ftdump", kdb_ftdump, "", "Dump ftrace log",
-                           0, KDB_REPEAT_NONE);
+       kdb_register_repeat("ftdump", kdb_ftdump, "[skip_#lines] [cpu]",
+                           "Dump ftrace log", 0, KDB_REPEAT_NONE);
        return 0;
 }