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Date: Thu, 7 Sep 2017 23:58:53 +0900
From: Namhyung Kim <namhyung@...nel.org>
To: Milian Wolff <milian.wolff@...b.com>
Cc: acme@...nel.org, Jin Yao <yao.jin@...ux.intel.com>,
Linux-kernel@...r.kernel.org, linux-perf-users@...r.kernel.org,
Arnaldo Carvalho de Melo <acme@...hat.com>,
David Ahern <dsahern@...il.com>,
Peter Zijlstra <a.p.zijlstra@...llo.nl>, kernel-team@....com
Subject: Re: [PATCH v2 03/14] perf report: create real callchain entries for
inlined frames
Hi Milian,
On Wed, Sep 06, 2017 at 03:13:35PM +0200, Milian Wolff wrote:
> 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.
But ilist->symbol is a dangling pointer so accessing ->inlined would
be a problem, no?
> 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.
Thanks for doing this, but I'm afraid I don't have time to review
before going to OSS-NA.
Thanks,
Namhyung
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