Re: [PATCH 2/2] perf report: report module before querying isactivation in dwfl unwind
From: Arnaldo Carvalho de Melo
Date: Fri Jun 16 2017 - 13:36:51 EST
Em Fri, Jun 16, 2017 at 01:06:52PM -0300, Arnaldo Carvalho de Melo escreveu:
> Em Fri, Jun 02, 2017 at 12:25:08PM -0300, Arnaldo Carvalho de Melo escreveu:
> > Em Fri, Jun 02, 2017 at 04:37:53PM +0200, Milian Wolff escreveu:
> > > The PC returned by dwfl_frame_pc may map into a not-yet-reported
> > > module. We have to report it before we continue unwinding. But when
> > > we query for the isactivation flag in dwfl_frame_pc, libdw will
> > > actually do one more unwinding step internally which can then break
> > > and lead to missed frames or broken stacks.
> > >
> > > With libunwind we get e.g.:
> >
> > Jiri, can you review this one?
>
> ping
Sorry, saw yesterday's replies now, will apply the patch with an
Acked-by: Jan.
Thanks,
- Arnaldo
> > Thanks,
> >
> > - Arnaldo
> >
> > > ~~~~~
> > > heaptrack_gui 2228 135073.400474: 613969 cycles:
> > > 108c8e [unknown] (/usr/lib/libQt5Core.so.5.8.0)
> > > 1093bc [unknown] (/usr/lib/libQt5Core.so.5.8.0)
> > > 109e7b QLocale::QLocale (/usr/lib/libQt5Core.so.5.8.0)
> > > 1470ff [unknown] (/usr/lib/libQt5Core.so.5.8.0)
> > > 147f67 QSystemLocale::query (/usr/lib/libQt5Core.so.5.8.0)
> > > 109fbf QLocalePrivate::updateSystemPrivate (/usr/lib/libQt5Core.so.5.8.0)
> > > 10aa27 QLocale::QLocale (/usr/lib/libQt5Core.so.5.8.0)
> > > 1e02c3 [unknown] (/usr/lib/libQt5Core.so.5.8.0)
> > > 2113bb [unknown] (/usr/lib/libQt5Core.so.5.8.0)
> > > 211505 [unknown] (/usr/lib/libQt5Core.so.5.8.0)
> > > 1b5df0 QFileInfo::exists (/usr/lib/libQt5Core.so.5.8.0)
> > > 92eb2 [unknown] (/usr/lib/libQt5Core.so.5.8.0)
> > > 93423 [unknown] (/usr/lib/libQt5Core.so.5.8.0)
> > > 93d2a QLibraryInfo::location (/usr/lib/libQt5Core.so.5.8.0)
> > > 2170af [unknown] (/usr/lib/libQt5Core.so.5.8.0)
> > > 297c53 QCoreApplicationPrivate::init (/usr/lib/libQt5Core.so.5.8.0)
> > > f7cde QGuiApplicationPrivate::init (/usr/lib/libQt5Gui.so.5.8.0)
> > > 1589e8 QApplicationPrivate::init (/usr/lib/libQt5Widgets.so.5.8.0)
> > > 78622 main (/home/milian/projects/compiled/other/bin/heaptrack_gui)
> > > 20439 __libc_start_main (/usr/lib/libc-2.25.so)
> > > 78299 _start (/home/milian/projects/compiled/other/bin/heaptrack_gui)
> > >
> > > heaptrack_gui 2228 135073.401156: 569521 cycles:
> > > 131633 QString::endsWith (/usr/lib/libQt5Core.so.5.8.0)
> > > 1a0701 QDir::cleanPath (/usr/lib/libQt5Core.so.5.8.0)
> > > 21b82d [unknown] (/usr/lib/libQt5Core.so.5.8.0)
> > > 1b3727 QFileInfo::canonicalFilePath (/usr/lib/libQt5Core.so.5.8.0)
> > > 2780c7 QFactoryLoader::update (/usr/lib/libQt5Core.so.5.8.0)
> > > 279525 QFactoryLoader::QFactoryLoader (/usr/lib/libQt5Core.so.5.8.0)
> > > e5bd0 QPlatformIntegrationFactory::create (/usr/lib/libQt5Gui.so.5.8.0)
> > > f5a1c QGuiApplicationPrivate::createPlatformIntegration (/usr/lib/libQt5Gui.so.5.8.0)
> > > f650c QGuiApplicationPrivate::createEventDispatcher (/usr/lib/libQt5Gui.so.5.8.0)
> > > 298524 QCoreApplicationPrivate::init (/usr/lib/libQt5Core.so.5.8.0)
> > > f7cde QGuiApplicationPrivate::init (/usr/lib/libQt5Gui.so.5.8.0)
> > > 1589e8 QApplicationPrivate::init (/usr/lib/libQt5Widgets.so.5.8.0)
> > > 78622 main (/home/milian/projects/compiled/other/bin/heaptrack_gui)
> > > 20439 __libc_start_main (/usr/lib/libc-2.25.so)
> > > 78299 _start (/home/milian/projects/compiled/other/bin/heaptrack_gui)
> > > ~~~~~
> > >
> > > Note the two frames 1589e8 and 78622 in the first sample. These are
> > > missing when unwinding with libdw. The second sample's breakage is
> > > more obvious:
> > >
> > > ~~~~~
> > > heaptrack_gui 2228 135073.400474: 613969 cycles:
> > > 108c8e [unknown] (/usr/lib/libQt5Core.so.5.8.0)
> > > 1093bc [unknown] (/usr/lib/libQt5Core.so.5.8.0)
> > > 109e7b QLocale::QLocale (/usr/lib/libQt5Core.so.5.8.0)
> > > 1470ff [unknown] (/usr/lib/libQt5Core.so.5.8.0)
> > > 147f67 QSystemLocale::query (/usr/lib/libQt5Core.so.5.8.0)
> > > 109fbf QLocalePrivate::updateSystemPrivate (/usr/lib/libQt5Core.so.5.8.0)
> > > 10aa27 QLocale::QLocale (/usr/lib/libQt5Core.so.5.8.0)
> > > 1e02c3 [unknown] (/usr/lib/libQt5Core.so.5.8.0)
> > > 2113bb [unknown] (/usr/lib/libQt5Core.so.5.8.0)
> > > 211505 [unknown] (/usr/lib/libQt5Core.so.5.8.0)
> > > 1b5df0 QFileInfo::exists (/usr/lib/libQt5Core.so.5.8.0)
> > > 92eb2 [unknown] (/usr/lib/libQt5Core.so.5.8.0)
> > > 93423 [unknown] (/usr/lib/libQt5Core.so.5.8.0)
> > > 93d2a QLibraryInfo::location (/usr/lib/libQt5Core.so.5.8.0)
> > > 2170af [unknown] (/usr/lib/libQt5Core.so.5.8.0)
> > > 297c53 QCoreApplicationPrivate::init (/usr/lib/libQt5Core.so.5.8.0)
> > > f7cde QGuiApplicationPrivate::init (/usr/lib/libQt5Gui.so.5.8.0)
> > > 20439 __libc_start_main (/usr/lib/libc-2.25.so)
> > > 78299 _start (/home/milian/projects/compiled/other/bin/heaptrack_gui)
> > >
> > > heaptrack_gui 2228 135073.401156: 569521 cycles:
> > > 131633 QString::endsWith (/usr/lib/libQt5Core.so.5.8.0)
> > > 1a0701 QDir::cleanPath (/usr/lib/libQt5Core.so.5.8.0)
> > > 21b82d [unknown] (/usr/lib/libQt5Core.so.5.8.0)
> > > 1b3727 QFileInfo::canonicalFilePath (/usr/lib/libQt5Core.so.5.8.0)
> > > 2780c7 QFactoryLoader::update (/usr/lib/libQt5Core.so.5.8.0)
> > > 279525 QFactoryLoader::QFactoryLoader (/usr/lib/libQt5Core.so.5.8.0)
> > > e5bd0 QPlatformIntegrationFactory::create (/usr/lib/libQt5Gui.so.5.8.0)
> > > 723dbf [unknown] ([unknown])
> > > ~~~~~
> > >
> > > This patch fixes this issue and the libdw unwinder mimicks the
> > > libunwind behavior more closely.
> > >
> > > Cc: Arnaldo Carvalho de Melo <acme@xxxxxxxxxx>
> > > Cc: Namhyung Kim <namhyung@xxxxxxxxxx>
> > > Cc: Jiri Olsa <jolsa@xxxxxxxxxx>
> > > Signed-off-by: Milian Wolff <milian.wolff@xxxxxxxx>
> > > ---
> > > tools/perf/util/unwind-libdw.c | 8 ++++++++
> > > 1 file changed, 8 insertions(+)
> > >
> > > diff --git a/tools/perf/util/unwind-libdw.c b/tools/perf/util/unwind-libdw.c
> > > index da45c4be5fb3..7755a5e0fe5e 100644
> > > --- a/tools/perf/util/unwind-libdw.c
> > > +++ b/tools/perf/util/unwind-libdw.c
> > > @@ -178,6 +178,14 @@ frame_callback(Dwfl_Frame *state, void *arg)
> > > Dwarf_Addr pc;
> > > bool isactivation;
> > >
> > > + if (!dwfl_frame_pc(state, &pc, NULL)) {
> > > + pr_err("%s", dwfl_errmsg(-1));
> > > + return DWARF_CB_ABORT;
> > > + }
> > > +
> > > + // report the module before we query for isactivation
> > > + report_module(pc, ui);
> > > +
> > > if (!dwfl_frame_pc(state, &pc, &isactivation)) {
> > > pr_err("%s", dwfl_errmsg(-1));
> > > return DWARF_CB_ABORT;
> > > --
> > > 2.13.0
> > --
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