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Sometimes when adding a kprobe by perf, it results in multiple probe
points, such as the following:
# ./perf probe -l
probe:vfs_getname (on getname_flags:73@fs/namei.c with pathname)
probe:vfs_getname_1 (on getname_flags:73@fs/namei.c with pathname)
probe:vfs_getname_2 (on getname_flags:73@fs/namei.c with pathname)
# cat /sys/kernel/debug/tracing/kprobe_events
p:probe/vfs_getname _text+5501804 pathname=+0(+0(%gpr31)):string
p:probe/vfs_getname_1 _text+5505388 pathname=+0(+0(%gpr31)):string
p:probe/vfs_getname_2 _text+5508396 pathname=+0(+0(%gpr31)):string
In this test, we need to record all of them and expect any of them in
the perf-script output, since it's not clear which one will be used for
the desired syscall:
# perf stat -e probe:vfs_getname\* -- touch /tmp/nic
Performance counter stats for 'touch /tmp/nic':
31 probe:vfs_getname_2
0 probe:vfs_getname_1
1 probe:vfs_getname
0.001421826 seconds time elapsed
0.001506000 seconds user
0.000000000 seconds sys
If the test relies only on probe:vfs_getname, it might easily miss the
relevant data.
Signed-off-by: Michael Petlan <mpetlan@redhat.com>
Cc: Jiri Olsa <jolsa@kernel.org>
LPU-Reference: 20200722135845.29958-1-mpetlan@redhat.com
Signed-off-by: Arnaldo Carvalho de Melo <acme@redhat.com>
Linux kernel
============
There are several guides for kernel developers and users. These guides can
be rendered in a number of formats, like HTML and PDF. Please read
Documentation/admin-guide/README.rst first.
In order to build the documentation, use ``make htmldocs`` or
``make pdfdocs``. The formatted documentation can also be read online at:
https://www.kernel.org/doc/html/latest/
There are various text files in the Documentation/ subdirectory,
several of them using the Restructured Text markup notation.
Please read the Documentation/process/changes.rst file, as it contains the
requirements for building and running the kernel, and information about
the problems which may result by upgrading your kernel.