[Xen-devel] [PATCH 2 of 3] xentrace: Add an option not to enable tracing

[George Dunlap <george.dunlap@xxxxxxxxxxxxx>]

Add an option that will set up the buffers and listen for updates,
but will not enable tracing.  This is useful if you have hacks
in Xen to enable tracing at key points (for example, debugging a shadow
bug).

Signed-off-by: George Dunlap <george.dunlap@xxxxxxxxxxxxx>

diff -r 16ef34de0129 -r ce0812566a4d tools/xentrace/xentrace.c
--- a/tools/xentrace/xentrace.c Tue Apr 13 17:24:07 2010 +0100
+++ b/tools/xentrace/xentrace.c Tue Apr 13 17:24:08 2010 +0100
@@ -58,7 +58,8 @@
     unsigned long timeout;
     unsigned long memory_buffer;
     uint8_t discard:1,
-        disable_tracing:1;
+        disable_tracing:1,
+        start_disabled:1;
 } settings_t;
 
 struct t_struct {
@@ -659,6 +660,10 @@
 
     /* setup access to trace buffers */
     get_tbufs(&tbufs_mfn, &tinfo_size);
+
+    if ( opts.start_disabled )
+        disable_tbufs();
+    
     tbufs = map_tbufs(tbufs_mfn, num, tinfo_size);
 
     size = tbufs->t_info->tbuf_size * XC_PAGE_SIZE;
@@ -791,6 +796,9 @@
 "                          it exits. Selecting this option will tell it to\n" \
 "                          keep tracing on.  Traces will be collected in\n" \
 "                          Xen's trace buffers until they become full.\n" \
+"  -X  --start-disabled    Setup trace buffers and listen, but don't enable\n" 
\
+"                          tracing. (Useful if tracing will be enabled by\n" \
+"                          else.)\n" \
 "  -T  --time-interval=s   Run xentrace for s seconds and quit.\n" \
 "  -?, --help              Show this message\n" \
 "  -V, --version           Print program version\n" \
@@ -914,12 +922,13 @@
         { "memory-buffer",  required_argument, 0, 'M' },
         { "discard-buffers", no_argument,      0, 'D' },
         { "dont-disable-tracing", no_argument, 0, 'x' },
+        { "start-disabled", no_argument,       0, 'X' },
         { "help",           no_argument,       0, '?' },
         { "version",        no_argument,       0, 'V' },
         { 0, 0, 0, 0 }
     };
 
-    while ( (option = getopt_long(argc, argv, "t:s:c:e:S:r:T:M:Dx?V",
+    while ( (option = getopt_long(argc, argv, "t:s:c:e:S:r:T:M:DxX?V",
                     long_options, NULL)) != -1) 
     {
         switch ( option )
@@ -957,6 +966,10 @@
             opts.disable_tracing = 0;
             break;
 
+        case 'X': /* Start disabled */
+            opts.start_disabled = 1;
+            break;
+
         case 'T':
             opts.timeout = argtol(optarg, 0);
             break;
@@ -993,6 +1006,7 @@
     opts.cpu_mask = 0;
     opts.disk_rsvd = 0;
     opts.disable_tracing = 1;
+    opts.start_disabled = 0;
     opts.timeout = 0;
 
     parse_args(argc, argv);

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