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| author | Alexey Dobriyan <adobriyan@gmail.com> | 2018-06-08 03:10:20 +0300 |
|---|---|---|
| committer | Linus Torvalds <torvalds@linux-foundation.org> | 2018-06-08 03:34:38 +0300 |
| commit | b2f5de0334f03e90ae7dee72a7fc597ef555a9a8 (patch) | |
| tree | 6eddd34b28ecd67582164b588f862951bf392680 /tools/testing/selftests/proc/.gitignore | |
| parent | 5d008fb414f7c73e0761835d941943e17d32463d (diff) | |
| download | linux-b2f5de0334f03e90ae7dee72a7fc597ef555a9a8.tar.xz | |
tools/testing/selftests/proc: test /proc/*/fd a bit (+ PF_KTHREAD is ABI!)
* Test lookup in /proc/self/fd.
"map_files" lookup story showed that lookup is not that simple.
* Test that all those symlinks open the same file.
Check with (st_dev, st_info).
* Test that kernel threads do not have anything in their /proc/*/fd/
directory.
Now this is where things get interesting.
First, kernel threads aren't pinned by /proc/self or equivalent,
thus some "atomicity" is required.
Second, ->comm can contain whitespace and ')'.
No, they are not escaped.
Third, the only reliable way to check if process is kernel thread
appears to be field #9 in /proc/*/stat.
This field is struct task_struct::flags in decimal!
Check is done by testing PF_KTHREAD flags like we do in kernel.
PF_KTREAD value is a part of userspace ABI !!!
Other methods for determining kernel threadness are not reliable:
* RSS can be 0 if everything is swapped, even while reading
from /proc/self.
* ->total_vm CAN BE ZERO if process is finishing
munmap(NULL, whole address space);
* /proc/*/maps and similar files can be empty because unmapping
everything works. Read returning 0 can't distinguish between
kernel thread and such suicide process.
Link: http://lkml.kernel.org/r/20180505000414.GA15090@avx2
Signed-off-by: Alexey Dobriyan <adobriyan@gmail.com>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>
Diffstat (limited to 'tools/testing/selftests/proc/.gitignore')
| -rw-r--r-- | tools/testing/selftests/proc/.gitignore | 3 |
1 files changed, 3 insertions, 0 deletions
diff --git a/tools/testing/selftests/proc/.gitignore b/tools/testing/selftests/proc/.gitignore index 6c16f77c722c..74e5912e9f2e 100644 --- a/tools/testing/selftests/proc/.gitignore +++ b/tools/testing/selftests/proc/.gitignore @@ -1,3 +1,6 @@ +/fd-001-lookup +/fd-002-posix-eq +/fd-003-kthread /proc-loadavg-001 /proc-self-map-files-001 /proc-self-map-files-002 |