mirror of
https://git.kernel.org/pub/scm/linux/kernel/git/next/linux-next.git
synced 2025-01-06 05:02:31 +00:00
The linux-next integration testing tree
bc9c806e52
For perf recording, it retrieves process info by iterating nodes in proc fs. If we run perf in a non-root PID namespace with command: # unshare --fork --pid perf record -e cycles -a -- test_program ... in this case, unshare command creates a child PID namespace and launches perf tool in it, but the issue is the proc fs is not mounted for the non-root PID namespace, this leads to the perf tool gathering process info from its parent PID namespace. We can use below command to observe the process nodes under proc fs: # unshare --pid --fork ls /proc 1 137 1968 2128 3 342 48 62 78 crypto kcore net uptime 10 138 2 2142 30 35 49 63 8 devices keys pagetypeinfo version 11 139 20 2143 304 36 50 64 82 device-tree key-users partitions vmallocinfo 12 14 2011 22 305 37 51 65 83 diskstats kmsg self vmstat 128 140 2038 23 307 39 52 656 84 driver kpagecgroup slabinfo zoneinfo 129 15 2074 24 309 4 53 67 9 execdomains kpagecount softirqs 13 16 2094 241 31 40 54 68 asound fb kpageflags stat 130 164 2096 242 310 41 55 69 buddyinfo filesystems loadavg swaps 131 17 2098 25 317 42 56 70 bus fs locks sys 132 175 21 26 32 43 57 71 cgroups interrupts meminfo sysrq-trigger 133 179 2102 263 329 44 58 75 cmdline iomem misc sysvipc 134 1875 2103 27 330 45 59 76 config.gz ioports modules thread-self 135 19 2117 29 333 46 6 77 consoles irq mounts timer_list 136 1941 2121 298 34 47 60 773 cpuinfo kallsyms mtd tty So it shows many existed tasks, since unshared command has not mounted the proc fs for the new created PID namespace, it still accesses the proc fs of the root PID namespace. This leads to two prominent issues: - Firstly, PID values are mismatched between thread info and samples. The gathered thread info are coming from the proc fs of the root PID namespace, but samples record its PID from the child PID namespace. - The second issue is profiled program 'test_program' returns its forked PID number from the child PID namespace, perf tool wrongly uses this PID number to retrieve the process info via the proc fs of the root PID namespace. To avoid issues, we need to mount proc fs for the child PID namespace with the option '--mount-proc' when use unshare command: # unshare --fork --pid --mount-proc perf record -e cycles -a -- test_program Conversely, when the proc fs of the root PID namespace is used by child namespace, perf tool can detect the multiple PID levels and nsinfo__is_in_root_namespace() returns false, this patch reports error for this case: # unshare --fork --pid perf record -e cycles -a -- test_program Couldn't synthesize bpf events. Perf runs in non-root PID namespace but it tries to gather process info from its parent PID namespace. Please mount the proc file system properly, e.g. add the option '--mount-proc' for unshare command. Reviewed-by: James Clark <james.clark@arm.com> Signed-off-by: Leo Yan <leo.yan@linaro.org> Cc: Alexander Shishkin <alexander.shishkin@linux.intel.com> Cc: Alexei Starovoitov <ast@kernel.org> Cc: Andrii Nakryiko <andrii@kernel.org> Cc: Daniel Borkmann <daniel@iogearbox.net> Cc: Ian Rogers <irogers@google.com> Cc: Ingo Molnar <mingo@redhat.com> Cc: Jiri Olsa <jolsa@redhat.com> Cc: John Fastabend <john.fastabend@gmail.com> Cc: KP Singh <kpsingh@kernel.org> Cc: Mark Rutland <mark.rutland@arm.com> Cc: Martin KaFai Lau <kafai@fb.com> Cc: Namhyung Kim <namhyung@kernel.org> Cc: Peter Zijlstra <peterz@infradead.org> Cc: Song Liu <songliubraving@fb.com> Cc: Yonghong Song <yhs@fb.com> Link: https://lore.kernel.org/r/20211224124014.2492751-1-leo.yan@linaro.org Signed-off-by: Arnaldo Carvalho de Melo <acme@redhat.com> |
||
|---|---|---|
| arch | ||
| block | ||
| certs | ||
| crypto | ||
| Documentation | ||
| drivers | ||
| fs | ||
| include | ||
| init | ||
| ipc | ||
| kernel | ||
| lib | ||
| LICENSES | ||
| mm | ||
| net | ||
| samples | ||
| scripts | ||
| security | ||
| sound | ||
| tools | ||
| usr | ||
| virt | ||
| .clang-format | ||
| .cocciconfig | ||
| .get_maintainer.ignore | ||
| .gitattributes | ||
| .gitignore | ||
| .mailmap | ||
| COPYING | ||
| CREDITS | ||
| Kbuild | ||
| Kconfig | ||
| MAINTAINERS | ||
| Makefile | ||
| README | ||
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.