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author | Alexey Dobriyan <adobriyan@gmail.com> | 2018-06-07 17:10:20 -0700 |
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committer | Linus Torvalds <torvalds@linux-foundation.org> | 2018-06-07 17:34:38 -0700 |
commit | b2f5de0334f03e90ae7dee72a7fc597ef555a9a8 (patch) | |
tree | 6eddd34b28ecd67582164b588f862951bf392680 /tools/testing/selftests/proc/proc-uptime.h | |
parent | proc: use "unsigned int" for /proc/*/stack (diff) | |
download | linux-dev-b2f5de0334f03e90ae7dee72a7fc597ef555a9a8.tar.xz linux-dev-b2f5de0334f03e90ae7dee72a7fc597ef555a9a8.zip |
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/proc-uptime.h')
-rw-r--r-- | tools/testing/selftests/proc/proc-uptime.h | 16 |
1 files changed, 1 insertions, 15 deletions
diff --git a/tools/testing/selftests/proc/proc-uptime.h b/tools/testing/selftests/proc/proc-uptime.h index 0e464b50e9d9..dc6a42b1d6b0 100644 --- a/tools/testing/selftests/proc/proc-uptime.h +++ b/tools/testing/selftests/proc/proc-uptime.h @@ -20,21 +20,7 @@ #include <stdlib.h> #include <unistd.h> -static unsigned long long xstrtoull(const char *p, char **end) -{ - if (*p == '0') { - *end = (char *)p + 1; - return 0; - } else if ('1' <= *p && *p <= '9') { - unsigned long long val; - - errno = 0; - val = strtoull(p, end, 10); - assert(errno == 0); - return val; - } else - assert(0); -} +#include "proc.h" static void proc_uptime(int fd, uint64_t *uptime, uint64_t *idle) { |