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SubjectRe: [PATCH v2 03/14] perf report: create real callchain entries for inlined frames
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On Sonntag, 20. August 2017 22:57:17 CEST Milian Wolff wrote:
> On Mittwoch, 16. August 2017 09:53:13 CEST Namhyung Kim wrote:
> > Hi Milian,
> >
> > On Sun, Aug 06, 2017 at 11:24:35PM +0200, Milian Wolff wrote:
> > > The inlined frames use a fake symbol that is tracked in a special
> > > map inside the dso, which is always sorted by name. All other
> >
> > It seems the above is not true. Fake symbols are maintained by
> > inline_node which in turn maintained by dso->inlines tree.
>
> OK, I'll rephrase this to make it more explicit. But what I call "map" is
> what you call "tree", no?
>
> <snip>
>
> > > @@ -201,7 +202,8 @@ static inline void callchain_cursor_reset(struct
> > > callchain_cursor *cursor)>
> > >
> > > int callchain_cursor_append(struct callchain_cursor *cursor, u64 ip,
> > >
> > > struct map *map, struct symbol *sym,
> > > bool branch, struct branch_flags *flags,
> > >
> > > - int nr_loop_iter, int samples, u64 branch_from);
> > > + int nr_loop_iter, int samples, u64 branch_from,
> > > + const char *srcline);
> > >
> > > /* Close a cursor writing session. Initialize for the reader */
> > > static inline void callchain_cursor_commit(struct callchain_cursor
> > > *cursor)
> >
> > I think it'd be better splitting srcline change into a separate
> > commit.
>
> OK, I'll try to see how this goes. It would simply add the boiler plate code
> to pass the srcline around, and then set it from within the callchain code,
> right?
>
> > > diff --git a/tools/perf/util/dso.c b/tools/perf/util/dso.c
> > > index b9e087fb8247..72e6e390fd26 100644
> > > --- a/tools/perf/util/dso.c
> > > +++ b/tools/perf/util/dso.c
> > > @@ -9,6 +9,7 @@
> > >
> > > #include "compress.h"
> > > #include "path.h"
> > > #include "symbol.h"
> > >
> > > +#include "srcline.h"
> > >
> > > #include "dso.h"
> > > #include "machine.h"
> > > #include "auxtrace.h"
> > >
> > > @@ -1233,6 +1234,7 @@ void dso__delete(struct dso *dso)
> > >
> > > dso->long_name);
> > >
> > > for (i = 0; i < MAP__NR_TYPES; ++i)
> > >
> > > symbols__delete(&dso->symbols[i]);
> > >
> > > + inlines__tree_delete(&dso->inlined_nodes);
> >
> > Hmm.. inline_node is released after symbol but it seems to have a
> > problem. Please see below.
> >
> > > if (dso->short_name_allocated) {
> > >
> > > zfree((char **)&dso->short_name);
> > >
> > > diff --git a/tools/perf/util/dso.h b/tools/perf/util/dso.h
> > > index f886141678eb..7d1e2b3c1f10 100644
> > > --- a/tools/perf/util/dso.h
> > > +++ b/tools/perf/util/dso.h
> > > @@ -141,6 +141,7 @@ struct dso {
> > >
> > > struct rb_root *root; /* root of rbtree that rb_node is in
>
> */
>
> > > struct rb_root symbols[MAP__NR_TYPES];
> > > struct rb_root symbol_names[MAP__NR_TYPES];
> > >
> > > + struct rb_root inlined_nodes;
> > >
> > > struct {
> > >
> > > u64 addr;
> > > struct symbol *symbol;
> >
> > [SNIP]
> >
> > > diff --git a/tools/perf/util/machine.c b/tools/perf/util/machine.c
> > > index d4df353051af..a7f8499c8756 100644
> > > --- a/tools/perf/util/machine.c
> > > +++ b/tools/perf/util/machine.c
> > > diff --git a/tools/perf/util/srcline.c b/tools/perf/util/srcline.c
> > > index ebc88a74e67b..a1fdf035d1dd 100644
> > > --- a/tools/perf/util/srcline.c
> > > +++ b/tools/perf/util/srcline.c
> > > @@ -33,28 +33,17 @@ static const char *dso__name(struct dso *dso)
> > >
> > > return dso_name;
> > >
> > > }
> > >
> > > -static int inline_list__append(char *filename, char *funcname, int
> > > line_nr, - struct inline_node *node, struct dso *dso)
> > > +static int inline_list__append(struct symbol *symbol, char *srcline,
> > > + struct inline_node *node)
> > >
> > > {
> > >
> > > struct inline_list *ilist;
> > >
> > > - char *demangled;
> > >
> > > ilist = zalloc(sizeof(*ilist));
> > > if (ilist == NULL)
> > >
> > > return -1;
> > >
> > > - ilist->filename = filename;
> > > - ilist->line_nr = line_nr;
> > > -
> > > - if (dso != NULL) {
> > > - demangled = dso__demangle_sym(dso, 0, funcname);
> > > - if (demangled == NULL) {
> > > - ilist->funcname = funcname;
> > > - } else {
> > > - ilist->funcname = demangled;
> > > - free(funcname);
> > > - }
> > > - }
> > > + ilist->symbol = symbol;
> > > + ilist->srcline = srcline;
> > >
> > > if (callchain_param.order == ORDER_CALLEE)
> > >
> > > list_add_tail(&ilist->list, &node->val);
> > >
> > > @@ -64,6 +53,30 @@ static int inline_list__append(char *filename, char
> > > *funcname, int line_nr,>
> > >
> > > return 0;
> > >
> > > }
> > >
> > > +// basename version that takes a const input string
> > > +static const char *gnu_basename(const char *path)
> > > +{
> > > + const char *base = strrchr(path, '/');
> > > +
> > > + return base ? base + 1 : path;
> > > +}
> > > +
> > > +static char *srcline_from_fileline(const char *file, unsigned int line)
> > > +{
> > > + char *srcline;
> > > +
> > > + if (!file)
> > > + return NULL;
> > > +
> > > + if (!srcline_full_filename)
> > > + file = gnu_basename(file);
> > > +
> > > + if (asprintf(&srcline, "%s:%u", file, line) < 0)
> > > + return NULL;
> > > +
> > > + return srcline;
> > > +}
> > > +
> > >
> > > #ifdef HAVE_LIBBFD_SUPPORT
> > >
> > > /*
> > >
> > > @@ -203,19 +216,55 @@ static void addr2line_cleanup(struct a2l_data
> > > *a2l)
> > >
> > > #define MAX_INLINE_NEST 1024
> > >
> > > +static struct symbol *new_inline_sym(struct dso *dso,
> > > + struct symbol *base_sym,
> > > + const char *funcname)
> > > +{
> > > + struct symbol *inline_sym;
> > > + char *demangled = NULL;
> > > +
> > > + if (dso) {
> > > + demangled = dso__demangle_sym(dso, 0, funcname);
> > > + if (demangled)
> > > + funcname = demangled;
> > > + }
> > > +
> > > + if (strcmp(funcname, base_sym->name) == 0) {
> > > + // reuse the real, existing symbol
> > > + inline_sym = base_sym;
> >
> > So inline_node could refer the existing symbol.
>
> Yes, that does indeed seem to be an issue. I wonder why I'm not seeing any
> crashes or valgrind/ASAN reports though. I'll have to dig into this.
>
> > > + } else {
> > > + // create a fake symbol for the inline frame
> > > + inline_sym = symbol__new(base_sym ? base_sym->start : 0,
> > > + base_sym ? base_sym->end : 0,
> > > + base_sym ? base_sym->binding : 0,
> > > + funcname);
> > > + if (inline_sym)
> > > + inline_sym->inlined = 1;
> > > + }
> > > +
> > > + free(demangled);
> > > +
> > > + return inline_sym;
> > > +}
> > > +
> > >
> > > static int inline_list__append_dso_a2l(struct dso *dso,
> > >
> > > - struct inline_node *node)
> > > + struct inline_node *node,
> > > + struct symbol *sym)
> > >
> > > {
> > >
> > > struct a2l_data *a2l = dso->a2l;
> > >
> > > - char *funcname = a2l->funcname ? strdup(a2l->funcname) : NULL;
> > > - char *filename = a2l->filename ? strdup(a2l->filename) : NULL;
> > > + struct symbol *inline_sym = new_inline_sym(dso, sym, a2l->funcname);
> > > + char *srcline = NULL;
> > > +
> > > + if (a2l->filename)
> > > + srcline = srcline_from_fileline(a2l->filename, a2l->line);
> > >
> > > - return inline_list__append(filename, funcname, a2l->line, node, dso);
> > > + return inline_list__append(inline_sym, srcline, node);
> > >
> > > }
> >
> > [SNIP]
> >
> > > @@ -511,10 +563,63 @@ void inline_node__delete(struct inline_node *node)
> > >
> > > list_for_each_entry_safe(ilist, tmp, &node->val, list) {
> > >
> > > list_del_init(&ilist->list);
> > >
> > > - zfree(&ilist->filename);
> > > - zfree(&ilist->funcname);
> > > + zfree(&ilist->srcline);
> > > + // only the inlined symbols are owned by the list
> > > + if (ilist->symbol && ilist->symbol->inlined)
> > > + symbol__delete(ilist->symbol);
> >
> > Existing symbols are released at this moment.
>
> Thanks for the review, I'll try to look into these issues once I have more
> time again.

OK, so I just dug into this part of the patch again. I don't think it's
actually a problem after all:

When an inline node reuses the real symbol, that symbol won't have its
`inlined` member set to true. Thus these symbols will never get deleted by
inline_node__delete. If you have suggestions on how to make this clearer, I'm
all ears. For now, I'll add a comment to where we alias/reuse the symbol.

I'll try to split up the patch now to make it somehow easier to review.

Cheers

--
Milian Wolff | milian.wolff@kdab.com | Senior Software Engineer
KDAB (Deutschland) GmbH&Co KG, a KDAB Group company
Tel: +49-30-521325470
KDAB - The Qt Experts


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