[PATCH] Fix strace -T

[PATCH] Fix strace -T

[Jon TURNEY]

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strace -T to toggle stracing of a process doesn't seem to work at the moment. 
Attached is a patch to make it work again.

2011-09-08  Jon TURNEY  <jon.turney@dronecode.org.uk>

	* include/sys/strace.h (strace): Add toggle() method
	* strace.cc (toggle): Implement toggle() method
	* sigproc.cc (wait_sig): Use strace.toggle() in __SIGSTRACE



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Fix 'strace -T -pid=<pid>'

Index: cygwin/include/sys/strace.h
===================================================================
--- cygwin/include/sys/strace.h.orig
+++ cygwin/include/sys/strace.h
@@ -40,6 +40,7 @@ class strace
   unsigned char _active;
 public:
   void activate ();
+  void toggle ();
   strace () {activate ();}
   int microseconds ();
   int version;
Index: cygwin/sigproc.cc
===================================================================
--- cygwin/sigproc.cc.orig
+++ cygwin/sigproc.cc
@@ -1194,7 +1194,7 @@ wait_sig (VOID *)
 	  talktome (&pack.si);
 	  break;
 	case __SIGSTRACE:
-	  strace.activate ();
+	  strace.toggle ();
 	  strace.hello ();
 	  break;
 	case __SIGPENDING:
Index: cygwin/strace.cc
===================================================================
--- cygwin/strace.cc.orig
+++ cygwin/strace.cc
@@ -43,6 +43,21 @@ strace::activate ()
 }
 
 void
+strace::toggle()
+{
+  if (active())
+    {
+      /* turn off stracing */
+      _active ^= 1;
+    }
+  else
+    {
+      /* announcing _STRACE_INTERFACE_ACTIVATE_ADDR makes the stracer turn on stracing */
+      activate ();
+    }
+}
+
+void
 strace::hello ()
 {
   if (active ())

Re: [PATCH] Fix strace -T

[Christopher Faylor]

On Thu, Sep 08, 2011 at 07:37:29PM +0100, Jon TURNEY wrote:
>
>strace -T to toggle stracing of a process doesn't seem to work at the moment. 
>Attached is a patch to make it work again.
>
>2011-09-08  Jon TURNEY  <jon.turney@dronecode.org.uk>
>
>	* include/sys/strace.h (strace): Add toggle() method
>	* strace.cc (toggle): Implement toggle() method
>	* sigproc.cc (wait_sig): Use strace.toggle() in __SIGSTRACE

IIRC, the intent was for hello() to toggle (in which case I guess it
should be hellogoodbye).  Why do you even need this functionality?
I'd just as soon remove it.

cgf

Re: [PATCH] Fix strace -T

[Jon TURNEY]

On 08/09/2011 20:09, Christopher Faylor wrote:
> On Thu, Sep 08, 2011 at 07:37:29PM +0100, Jon TURNEY wrote:
>>
>> strace -T to toggle stracing of a process doesn't seem to work at the moment.
>> Attached is a patch to make it work again.
>>
>> 2011-09-08  Jon TURNEY<jon.turney@dronecode.org.uk>
>>
>> 	* include/sys/strace.h (strace): Add toggle() method
>> 	* strace.cc (toggle): Implement toggle() method
>> 	* sigproc.cc (wait_sig): Use strace.toggle() in __SIGSTRACE
>
> IIRC, the intent was for hello() to toggle (in which case I guess it
> should be hellogoodbye).  Why do you even need this functionality?
> I'd just as soon remove it.

I found it very helpful to have this working when I was looking at a problem 
which occurred when running the twisted testsuite ([1], I think), as running 
the entire testsuite with strace enabled greatly slowed it down and generated 
a vast amount of output, and the problem did not reproduce when running a 
single test.  Being able to disable strace output until close to the point of 
failure was useful.

I didn't want to touch strace::hello() as it's called from a few other places 
than __SIGSTRACE processing, and I don't understand them well enough to know 
if toggling in those places is correct.

[1] http://cygwin.com/ml/cygwin/2011-03/msg00437.html