Messages in this thread | | | Date | Fri, 20 Mar 2015 10:26:15 -0300 | From | Arnaldo Carvalho de Melo <> | Subject | Re: [PATCH] perf: fix race in build_id_cache__add_s() |
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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 <jolsa@kernel.org> > > 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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