Re: [PATCH 2/3] libtracefs: Add tracefs_function_notrace() API

[Steven Rostedt <rostedt@goodmis.org>]

On Thu, 8 Apr 2021 07:25:20 +0300
Tzvetomir Stoyanov <tz.stoyanov@gmail.com> wrote:

> > diff --git a/src/tracefs-instance.c b/src/tracefs-instance.c
> > index bf2fabf..9f45624 100644
> > --- a/src/tracefs-instance.c
> > +++ b/src/tracefs-instance.c
> > @@ -44,6 +44,7 @@ static struct tracefs_instance *instance_alloc(const char *trace_dir, const char
> >         }
> >
> >         instance->ftrace_filter_fd = -1;
> > +       instance->ftrace_notrace_fd = -1;  
> 
> These descriptors should be closed in tracefs_instance_free(), as part
> of the instance cleanup.

Good point. I'll add a patch on top of this one to close both of them.

> 
> >
> >         return instance;
> >
> > diff --git a/src/tracefs-tools.c b/src/tracefs-tools.c
> > index 21a9bd3..b41806b 100644
> > --- a/src/tracefs-tools.c
> > +++ b/src/tracefs-tools.c
> > @@ -21,10 +21,12 @@
> >
> >  #define TRACE_CTRL             "tracing_on"
> >  #define TRACE_FILTER           "set_ftrace_filter"
> > +#define TRACE_NOTRACE          "set_ftrace_notrace"
> >  #define TRACE_FILTER_LIST      "available_filter_functions"
> >
> >  /* File descriptor for Top level set_ftrace_filter  */
> >  static int ftrace_filter_fd = -1;
> > +static int ftrace_notrace_fd = -1;
> >  static pthread_mutex_t filter_lock = PTHREAD_MUTEX_INITIALIZER;  
> 
> I'm wondering if we should free these global resources somehow. A
> cleanup API for the whole library can be implemented  using
> __attribute__((destructor)), or some other way ?

No need. The OS will close them for you when the application exits. All
file descriptors that are opened will be closed by the OS.

That said, we should probably add O_CLOEXEC in the open for them such that
they don't stay open if the application does an exec() system call.

-- Steve