Messages in this thread Patch in this message | | | Subject | [PATCH perf/core 17/22] perf: Fix __machine__addnew_vdso to put dso after add to dsos | From | Masami Hiramatsu <> | Date | Wed, 09 Dec 2015 11:11:25 +0900 |
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Fix __machine__addnew_vdso to put dso after add to dsos because the dso is already gotten by the dsos via __dsos__add().
This function is called finally from machine__findnew_vdso() which locks machine->dsos.lock. And before unlock it, the function gets the dso's refcnt. Thus we can ensure that the dso is not removed from the machine while this operation, and we don't need to get the dso except for the machine->dsos.
refcnt debugger shows: ----- $ ./perf top --stdio -v (note: run by non-root user) [...] ==== [3] ==== Unreclaimed dso@0x27a0a30 Refcount +1 => 1 at ./perf(dso__new+0x2bc) [0x4a778c] ./perf(machine__findnew_vdso+0x272) [0x4e8792] ./perf(map__new+0x2db) [0x4bfb4b] ./perf(machine__process_mmap2_event+0xf3) [0x4bda33] ./perf(perf_event__synthesize_mmap_events+0x364) [0x484e74] ./perf(perf_event__synthesize_threads+0x3ee) [0x48583e] ./perf(cmd_top+0xdc2) [0x43cfb2] ./perf() [0x47ba35] ./perf(main+0x617) [0x4225b7] /lib64/libc.so.6(__libc_start_main+0xf5) [0x7f2b01387af5] ./perf() [0x42272d] Refcount +1 => 2 at ./perf(machine__findnew_vdso+0x289) [0x4e87a9] ./perf(map__new+0x2db) [0x4bfb4b] ./perf(machine__process_mmap2_event+0xf3) [0x4bda33] ./perf(perf_event__synthesize_mmap_events+0x364) [0x484e74] ./perf(perf_event__synthesize_threads+0x3ee) [0x48583e] ./perf(cmd_top+0xdc2) [0x43cfb2] ./perf() [0x47ba35] ./perf(main+0x617) [0x4225b7] /lib64/libc.so.6(__libc_start_main+0xf5) [0x7f2b01387af5] ./perf() [0x42272d] Refcount +1 => 3 at ./perf(dso__get+0x32) [0x4a7b52] ./perf(machine__findnew_vdso+0xc1) [0x4e85e1] ./perf(map__new+0x2db) [0x4bfb4b] ./perf(machine__process_mmap2_event+0xf3) [0x4bda33] ./perf(perf_event__synthesize_mmap_events+0x364) [0x484e74] ./perf(perf_event__synthesize_threads+0x3ee) [0x48583e] ./perf(cmd_top+0xdc2) [0x43cfb2] ./perf() [0x47ba35] ./perf(main+0x617) [0x4225b7] /lib64/libc.so.6(__libc_start_main+0xf5) [0x7f2b01387af5] ./perf() [0x42272d] [...] -----
The log shows that the machine__findnew_vdso gets a dso so many unnaturally. I've traced the code and found this bug.
Signed-off-by: Masami Hiramatsu <masami.hiramatsu.pt@hitachi.com> --- tools/perf/util/vdso.c | 2 ++ 1 file changed, 2 insertions(+)
diff --git a/tools/perf/util/vdso.c b/tools/perf/util/vdso.c index 44d440d..fea0d18 100644 --- a/tools/perf/util/vdso.c +++ b/tools/perf/util/vdso.c @@ -130,6 +130,8 @@ static struct dso *__machine__addnew_vdso(struct machine *machine, const char *s __dsos__add(&machine->dsos, dso); dso__set_long_name(dso, long_name, false); } + /* Put the dso here because it is already gotten by __dsos__add */ + dso__put(dso); return dso; }
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