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    SubjectRe: tracepoint filter problems
    On Thu, Oct 29, 2015 at 12:27:42PM -0300, Arnaldo Carvalho de Melo wrote:
    > Hi,
    >
    > In 'perf trace' we have an equivalent to strace's -e option, i.e. a way
    > to state which syscalls one wants to see, so, when we do:
    >
    > [root@felicio linux]# trace -e open
    > 0.348 ( 0.005 ms): ls/6887 open(filename: /etc/ld.so.cache, flags: CLOEXEC ) = 3
    > 0.363 ( 0.005 ms): ls/6887 open(filename: /lib64/libselinux.so.1, flags: CLOEXEC ) = 3
    > 0.400 ( 0.006 ms): ls/6887 open(filename: /lib64/libcap.so.2, flags: CLOEXEC ) = 3
    > 0.427 ( 0.006 ms): ls/6887 open(filename: /lib64/libacl.so.1, flags: CLOEXEC ) = 3
    > 0.454 ( 0.006 ms): ls/6887 open(filename: /lib64/libc.so.6, flags: CLOEXEC ) = 3
    > 0.497 ( 0.006 ms): ls/6887 open(filename: /lib64/libpcre.so.1, flags: CLOEXEC ) = 3
    > 0.533 ( 0.006 ms): ls/6887 open(filename: /lib64/liblzma.so.5, flags: CLOEXEC ) = 3
    > 0.561 ( 0.006 ms): ls/6887 open(filename: /lib64/libdl.so.2, flags: CLOEXEC ) = 3
    > 0.586 ( 0.006 ms): ls/6887 open(filename: /lib64/libattr.so.1, flags: CLOEXEC ) = 3
    > 0.611 ( 0.006 ms): ls/6887 open(filename: /lib64/libpthread.so.0, flags: CLOEXEC ) = 3
    > 0.859 ( 0.007 ms): ls/6887 open(filename: /usr/lib/locale/locale-archive, flags: CLOEXEC ) = 3
    > ^C[root@felicio linux]#
    >
    > I.e. tracing system wide, looking for any program that calls the open syscall, it works, as it
    > used the PERF_EVENT_IOC_SET_FILTER to set the relevant 'id == 486' to filter it:
    >
    > [root@felicio linux]# head -2 /sys/kernel/debug/tracing/events/syscalls/sys_enter_open/format
    > name: sys_enter_open
    > ID: 486
    >
    > Ok, this is how it should be, all works, but if I try instead calling a program
    > that in turn calls another, the filter will apply for the first in line, but
    > not for the calls made by another program called from it.
    >
    > In the example below 'perf trace' will ask to see just the 'open' syscall, and
    > it works for the started workload, namely 'perf record', but then it'll call
    > 'sleep 100000000000' and there the filter doesn't apply, bummer :-\
    >
    > The inherit bit is set, sure, as we can see when adding -vv to the 'perf trace'
    > call, ideas?

    --- a/kernel/events/core.c
    +++ b/kernel/events/core.c
    @@ -6939,6 +6939,10 @@ static int perf_tp_filter_match(struct p
    {
    void *record = data->raw->data;

    + /* only top level events have filters set */
    + if (event->parent)
    + event = event->parent;
    +
    if (likely(!event->filter) || filter_match_preds(event->filter, record))
    return 1;
    return 0;

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