On Mon, May 14, 2012 at 05:18:58PM -0600, Eric Blake wrote:
> On 05/09/2012 08:22 AM, Daniel P. Berrange wrote:
> > From: "Daniel P. Berrange" <berrange@xxxxxxxxxx>
> >
> > Sometimes it is useful to see the callpath for log messages.
> > This change enhances the log filter syntax so that stck traces
>
> s/stck/stack/
>
> > can be show by setting '1:+NAME' instead of '1:NAME'.
>
> Cool.
>
> > * docs/logging.html.in: Document new syntax
> > * configure.ac: Check for execinfo.h
> > * src/util/logging.c, src/util/logging.h: Add support for
> > stack traces
>
> Of course, this seems to be Linux-only, but still useful.
Yep, glibc only, unless other platforms have equivalent APIs
we can use
>
> > +++ b/docs/logging.html.in
> > @@ -114,8 +114,10 @@
> > </h3>
> > <p>The syntax for filters and outputs is the same for both types of
> > variables.</p>
> > - <p>The format for a filter is:</p>
> > - <pre>x:name</pre>
> > + <p>The format for a filter is one of:</p>
> > + <pre>
> > + x:name (log message only)
> > + x:+name (log message + stack trace)</pre>
>
> Does x:+name error out on systems where tracing is not built in, or does
> it silently fall back to x:name?
It just logs a warning message instead of the stack trace
>
> > @@ -538,6 +546,7 @@ static int virLogFiltersCheck(const char *input) {
> > for (i = 0;i < virLogNbFilters;i++) {
> > if (strstr(input, virLogFilters[i].match)) {
> > ret = virLogFilters[i].priority;
> > + *flags = virLogFilters[i].flags;
>
> Is the double space intentional?
No.
> > +
> > +static void virLogStackTraceToFd(int fd)
> > +{
> > +#ifdef HAVE_EXECINFO_H
> > + void *array[100];
> > + int size;
> > +
> > +#define STRIP_DEPTH 3
> > +
> > + size = backtrace(array, sizeof(array)/sizeof(array[0]));
>
> Write the second argument as ARRAY_CARDINALITY(array).
>
> > + backtrace_symbols_fd(array + STRIP_DEPTH, size - STRIP_DEPTH, fd);
> > + ignore_value(safewrite(fd, "\n", 1));
> > +#else
> > + const char *msg = "stack trace not available on this platform";
> > + ignore_value(safewrite(fd, msg, strlen(msg)));
>
> Is this a one-time error message, printed on first use, or will it
> appear on every log message?
It is printed every time in place of the stack trace. I guess I should
make it one-time only.
Daniel
--
|: http://berrange.com -o- http://www.flickr.com/photos/dberrange/ :|
|: http://libvirt.org -o- http://virt-manager.org :|
|: http://autobuild.org -o- http://search.cpan.org/~danberr/ :|
|: http://entangle-photo.org -o- http://live.gnome.org/gtk-vnc :|
--
libvir-list mailing list
libvir-list@xxxxxxxxxx
https://www.redhat.com/mailman/listinfo/libvir-list