Em Fri, Mar 20, 2015 at 01:18:07PM +0100, Jiri Olsa escreveu:
> On Fri, Mar 20, 2015 at 11:37:25AM +0100, Milos Vyletel wrote:
> > int build_id_cache__add_s(const char *sbuild_id, const char *debugdir,
> > const char *name, bool is_kallsyms, bool is_vdso)
> > {
> > ...
> > if (access(filename, F_OK)) {
> > ^---------------------------------------------------------
> > [1]
> > if (is_kallsyms) {
> > if (copyfile("/proc/kallsyms", filename))
> > goto out_free;
> > } else if (link(realname, filename) && copyfile(name,
> > filename))
> > ^-----------------------------^-------------
> > [2]
> > \------------
> > [3]
> > goto out_free;
> > }
> > ...
> >
> > when multiple instances of perf record get to [1] at more or less same time
> > and
> > run access() one or more may get failure because the file does not exist yet
> > (since the first instance did not have chance to link it yet). at this
> > point the
> > race moves to link() at [2] where first thread to get there links file and
> > goes
> > on but second one gets -EEXIST so it runs copyfile [3] which truncates the
> > file.
>
> nice.. :-\
>
> Acked-by: Jiri Olsa <[email protected]>
>
> in addition we should use some inter-perf lock
> on all .debug dir operations
Yeah, would be nice to have that improved.
Thanks, applied.
- Arnaldo
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