Messages in this thread Patch in this message | | | Date | Mon, 09 Apr 2012 14:17:14 -0600 | From | David Ahern <> | Subject | Re: [BUG PATCH] perf: kvm - finding struct machine fails for PERF_RECORD_MMAP |
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On 4/9/12 2:22 AM, Nikunj A. Dadhania wrote: > From: Nikunj A. Dadhania<nikunj@linux.vnet.ibm.com> > > Running 'perf kvm --host --guest --guestmount /tmp/guestmount record -a -g -- sleep 2' > > Was resulting in a segfault. For event type PERF_RECORD_MMAP, > event->ip.pid is being used in perf_session__find_machine_for_cpumode, > which is not correct.
I'm not getting the segfault with latest tip/perf/urgent, but I am getting a hang.
It's stuck on buildid:
(gdb) bt #0 0x00007fabf53e79da in mmap64 () from /lib64/libc.so.6 #1 0x0000000000454656 in __perf_session__process_events (session=0x1e06110, data_offset=<value optimized out>, data_size=<value optimized out>, file_size=37328, tool=0x75db40) at util/session.c:1192 #2 0x00000000004102e6 in process_buildids (status=<value optimized out>, arg=0x75cc00) at builtin-record.c:320 #3 perf_record__exit (status=<value optimized out>, arg=0x75cc00) at builtin-record.c:333 #4 0x00007fabf53419c9 in exit () from /lib64/libc.so.6 #5 0x0000000000406b84 in handle_internal_command (argc=9, argv=0x7fff3f14d6c0) at perf.c:345 #6 run_argv (argc=9, argv=0x7fff3f14d6c0) at perf.c:389 #7 main (argc=9, argv=0x7fff3f14d6c0) at perf.c:487
Adding -B works around it and proves something is not right regarding buildid's and perf-kvm. I'll dig into it as time allows, but wanted to send this out in case Arnaldo understands the problem now.
David
> > event->ip.pid happens to be 0 in this case and results in returning a > NULL machine object. Finally, access to self->pid in > machine__mmap_name, results in a segfault later. > > For PERF_RECORD_MMAP type, pass event->mmap.pid. > > Signed-off-by: Nikunj A. Dadhania<nikunj@linux.vnet.ibm.com> > --- > > tools/perf/util/session.c | 12 ++++++++++-- > 1 files changed, 10 insertions(+), 2 deletions(-) > > diff --git a/tools/perf/util/session.c b/tools/perf/util/session.c > index 9412e3b..00923cd 100644 > --- a/tools/perf/util/session.c > +++ b/tools/perf/util/session.c > @@ -826,8 +826,16 @@ static struct machine * > { > const u8 cpumode = event->header.misc& PERF_RECORD_MISC_CPUMODE_MASK; > > - if (cpumode == PERF_RECORD_MISC_GUEST_KERNEL&& perf_guest) > - return perf_session__find_machine(session, event->ip.pid); > + if (cpumode == PERF_RECORD_MISC_GUEST_KERNEL&& perf_guest) { > + u32 pid; > + > + if (event->header.type == PERF_RECORD_MMAP) > + pid = event->mmap.pid; > + else > + pid = event->ip.pid; > + > + return perf_session__find_machine(session, pid); > + } > > return perf_session__find_host_machine(session); > } > > -- > To unsubscribe from this list: send the line "unsubscribe linux-kernel" in > the body of a message to majordomo@vger.kernel.org > More majordomo info at http://vger.kernel.org/majordomo-info.html > Please read the FAQ at http://www.tux.org/lkml/
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