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* Invisible threads in 2.6
@ 2004-05-25  2:21 lm240504
  2004-05-25  7:03 ` Martin Zwickel
  0 siblings, 1 reply; 3+ messages in thread
From: lm240504 @ 2004-05-25  2:21 UTC (permalink / raw)
  To: linux-kernel

I've been experimenting with process/thread accounting in 2.6.x,
and found this strange situation: if the leader thread of a multi-threaded
process terminates, the other threads become undetectable.  After the
main thread becomes a zombie, /proc/<tgid>/task returns ENOENT on
open.  If you happen to know the TID, you can access /proc/<tid>/* directly,
but otherwise, there is no way to observe the remaining threads, as far as
I can see.  Consider this program, for example:

#include <pthread.h>

void *run(void *arg)
{
        for(;;);
}

int main()
{
        pthread_t t;
        int i;
        for (i = 0; i < 10; ++i)
                pthread_create(&t, NULL, run, NULL);
        pthread_exit(NULL);
}

When I run it, the system (predictably) goes to ~100% CPU utilization,
but there seems to be no way to find out who is hogging the CPU with
top(1), ps(1), or anything else.  All they can show is the main thread in
zombie state, consuming 0% CPU.

I'm not sure how to fix this (the pid_alive() test seems to be there for a
reason), but it doesn't seem right.  Any thoughts?

^ permalink raw reply	[flat|nested] 3+ messages in thread
* Re: Invisible threads in 2.6
@ 2004-05-25 18:51 lm240504
  0 siblings, 0 replies; 3+ messages in thread
From: lm240504 @ 2004-05-25 18:51 UTC (permalink / raw)
  To: Martin Zwickel; +Cc: linux-kernel

[-- Attachment #1: Type: text/plain, Size: 1380 bytes --]

> my kernel:
> # cat /proc/version 
> Linux version 2.6.6-rc3-mm2 (root@phoebee) (gcc version 3.3.2 20031218 (Gentoo
> Linux 3.3.2-r5, propolice-3.3-7)) #6 Fri May 7 10:56:06 CEST 2004
> 
> I just compiled your example and ran it:
> # ./thread_test 
> 
<snip>
> On my -mm patched kernel I can see them.

I tried 2.6.6-rc3-mm2, and didn't see any difference:

# cat /proc/version
Linux version 2.6.6-rc3-mm2 (lmakhlis@levlinux) (gcc version 3.2.2 20030222 (Red Hat Linux 3.2.2-5)) #3 SMP Tue May 25 14:04:28 EDT 2004
                                                                                
# ./thread_test &
[749]
                                                                                
# ls /proc/749/task
ls: /proc/749/task: No such file or directory
                                                                                
# ps axw
...
  749 tty1     Z      0:00 [thread_test <defunct>]
...

I have now tested it on Fedora Core 2 (2.6.5), SLES 9 Beta (2.6.5) and RHL 9 w/ 2.6.6-rc3-mm2, with identical results.  Could it have anything to do with which thread library the program is using?  Here's mine:

# ldd ./thread_test
        libpthread.so.0 => /lib/tls/libpthread.so.0 (0x40028000)
        libc.so.6 => /lib/tls/libc.so.6 (0x42000000)
        /lib/ld-linux.so.2 => /lib/ld-linux.so.2 (0x40000000)

# strace ./pthread_test
<see attachment>

Lev




[-- Attachment #2: strace.out --]
[-- Type: application/octet-stream, Size: 6910 bytes --]

execve("./thread_test", ["./thread_test"], [/* 11 vars */]) = 0
uname({sys="Linux", node="levlinux", ...}) = 0
brk(0)                                  = 0x804a000
open("/etc/ld.so.preload", O_RDONLY)    = -1 ENOENT (No such file or directory)
open("/etc/ld.so.cache", O_RDONLY)      = 3
fstat64(3, {st_mode=S_IFREG|0644, st_size=69902, ...}) = 0
old_mmap(NULL, 69902, PROT_READ, MAP_PRIVATE, 3, 0) = 0x40016000
close(3)                                = 0
open("/lib/tls/libpthread.so.0", O_RDONLY) = 3
read(3, "\177ELF\1\1\1\0\0\0\0\0\0\0\0\0\3\0\3\0\1\0\0\0p?\0\000"..., 512) = 512
fstat64(3, {st_mode=S_IFREG|0755, st_size=80592, ...}) = 0
old_mmap(NULL, 54612, PROT_READ|PROT_EXEC, MAP_PRIVATE, 3, 0) = 0x40028000
old_mmap(0x40033000, 4096, PROT_READ|PROT_WRITE, MAP_PRIVATE|MAP_FIXED, 3, 0xa000) = 0x40033000
old_mmap(0x40034000, 5460, PROT_READ|PROT_WRITE, MAP_PRIVATE|MAP_FIXED|MAP_ANONYMOUS, -1, 0) = 0x40034000
close(3)                                = 0
open("/lib/tls/libc.so.6", O_RDONLY)    = 3
read(3, "\177ELF\1\1\1\0\0\0\0\0\0\0\0\0\3\0\3\0\1\0\0\0\360W\1"..., 512) = 512
fstat64(3, {st_mode=S_IFREG|0755, st_size=1539996, ...}) = 0
old_mmap(NULL, 4096, PROT_READ|PROT_WRITE, MAP_PRIVATE|MAP_ANONYMOUS, -1, 0) = 0x40036000
old_mmap(0x42000000, 1267276, PROT_READ|PROT_EXEC, MAP_PRIVATE, 3, 0) = 0x42000000
old_mmap(0x42130000, 12288, PROT_READ|PROT_WRITE, MAP_PRIVATE|MAP_FIXED, 3, 0x130000) = 0x42130000
old_mmap(0x42133000, 9804, PROT_READ|PROT_WRITE, MAP_PRIVATE|MAP_FIXED|MAP_ANONYMOUS, -1, 0) = 0x42133000
close(3)                                = 0
set_thread_area({entry_number:-1 -> 6, base_addr:0x400368a0, limit:1048575, seg_32bit:1, contents:0, read_exec_only:0, limit_in_pages:1, seg_not_present:0, useable:1}) = 0
munmap(0x40016000, 69902)               = 0
set_tid_address(0x400368e8)             = 729
rt_sigaction(SIGRTMIN, {0x4002bed0, [], SA_RESTORER, 0x400318f8}, NULL, 8) = 0
rt_sigprocmask(SIG_UNBLOCK, [RTMIN], NULL, 8) = 0
rt_sigprocmask(SIG_BLOCK, [33], NULL, 8) = 0
getrlimit(0x3, 0xbffffd14)              = 0
mmap2(NULL, 8392704, PROT_READ|PROT_WRITE|PROT_EXEC, MAP_PRIVATE|MAP_ANONYMOUS, -1, 0) = 0x40037000
brk(0)                                  = 0x804a000
brk(0x804b000)                          = 0x804b000
brk(0)                                  = 0x804b000
mprotect(0x40037000, 4096, PROT_NONE)   = 0
clone(child_stack=0x40837a90, flags=CLONE_VM|CLONE_FS|CLONE_FILES|CLONE_SIGHAND|CLONE_THREAD|CLONE_SETTLS|CLONE_PARENT_SETTID|CLONE_CHILD_CLEARTID|CLONE_DETACHED, [730], {entry_number:6, base_addr:0x40837b30, limit:1048575, seg_32bit:1, contents:0, read_exec_only:0, limit_in_pages:1, seg_not_present:0, useable:1}) = 730
mmap2(NULL, 8392704, PROT_READ|PROT_WRITE|PROT_EXEC, MAP_PRIVATE|MAP_ANONYMOUS, -1, 0) = 0x40838000
mprotect(0x40838000, 4096, PROT_NONE)   = 0
clone(child_stack=0x41038a90, flags=CLONE_VM|CLONE_FS|CLONE_FILES|CLONE_SIGHAND|CLONE_THREAD|CLONE_SETTLS|CLONE_PARENT_SETTID|CLONE_CHILD_CLEARTID|CLONE_DETACHED, [731], {entry_number:6, base_addr:0x41038b30, limit:1048575, seg_32bit:1, contents:0, read_exec_only:0, limit_in_pages:1, seg_not_present:0, useable:1}) = 731
mmap2(NULL, 8392704, PROT_READ|PROT_WRITE|PROT_EXEC, MAP_PRIVATE|MAP_ANONYMOUS, -1, 0) = 0x41039000
mprotect(0x41039000, 4096, PROT_NONE)   = 0
clone(child_stack=0x41839a90, flags=CLONE_VM|CLONE_FS|CLONE_FILES|CLONE_SIGHAND|CLONE_THREAD|CLONE_SETTLS|CLONE_PARENT_SETTID|CLONE_CHILD_CLEARTID|CLONE_DETACHED, [732], {entry_number:6, base_addr:0x41839b30, limit:1048575, seg_32bit:1, contents:0, read_exec_only:0, limit_in_pages:1, seg_not_present:0, useable:1}) = 732
mmap2(NULL, 8392704, PROT_READ|PROT_WRITE|PROT_EXEC, MAP_PRIVATE|MAP_ANONYMOUS, -1, 0) = 0x42136000
mprotect(0x42136000, 4096, PROT_NONE)   = 0
clone(child_stack=0x42936a90, flags=CLONE_VM|CLONE_FS|CLONE_FILES|CLONE_SIGHAND|CLONE_THREAD|CLONE_SETTLS|CLONE_PARENT_SETTID|CLONE_CHILD_CLEARTID|CLONE_DETACHED, [733], {entry_number:6, base_addr:0x42936b30, limit:1048575, seg_32bit:1, contents:0, read_exec_only:0, limit_in_pages:1, seg_not_present:0, useable:1}) = 733
mmap2(NULL, 8392704, PROT_READ|PROT_WRITE|PROT_EXEC, MAP_PRIVATE|MAP_ANONYMOUS, -1, 0) = 0x42937000
mprotect(0x42937000, 4096, PROT_NONE)   = 0
clone(child_stack=0x43137a90, flags=CLONE_VM|CLONE_FS|CLONE_FILES|CLONE_SIGHAND|CLONE_THREAD|CLONE_SETTLS|CLONE_PARENT_SETTID|CLONE_CHILD_CLEARTID|CLONE_DETACHED, [734], {entry_number:6, base_addr:0x43137b30, limit:1048575, seg_32bit:1, contents:0, read_exec_only:0, limit_in_pages:1, seg_not_present:0, useable:1}) = 734
mmap2(NULL, 8392704, PROT_READ|PROT_WRITE|PROT_EXEC, MAP_PRIVATE|MAP_ANONYMOUS, -1, 0) = 0x43138000
mprotect(0x43138000, 4096, PROT_NONE)   = 0
clone(child_stack=0x43938a90, flags=CLONE_VM|CLONE_FS|CLONE_FILES|CLONE_SIGHAND|CLONE_THREAD|CLONE_SETTLS|CLONE_PARENT_SETTID|CLONE_CHILD_CLEARTID|CLONE_DETACHED, [735], {entry_number:6, base_addr:0x43938b30, limit:1048575, seg_32bit:1, contents:0, read_exec_only:0, limit_in_pages:1, seg_not_present:0, useable:1}) = 735
mmap2(NULL, 8392704, PROT_READ|PROT_WRITE|PROT_EXEC, MAP_PRIVATE|MAP_ANONYMOUS, -1, 0) = 0x43939000
mprotect(0x43939000, 4096, PROT_NONE)   = 0
clone(child_stack=0x44139a90, flags=CLONE_VM|CLONE_FS|CLONE_FILES|CLONE_SIGHAND|CLONE_THREAD|CLONE_SETTLS|CLONE_PARENT_SETTID|CLONE_CHILD_CLEARTID|CLONE_DETACHED, [736], {entry_number:6, base_addr:0x44139b30, limit:1048575, seg_32bit:1, contents:0, read_exec_only:0, limit_in_pages:1, seg_not_present:0, useable:1}) = 736
mmap2(NULL, 8392704, PROT_READ|PROT_WRITE|PROT_EXEC, MAP_PRIVATE|MAP_ANONYMOUS, -1, 0) = 0x4413a000
mprotect(0x4413a000, 4096, PROT_NONE)   = 0
clone(child_stack=0x4493aa90, flags=CLONE_VM|CLONE_FS|CLONE_FILES|CLONE_SIGHAND|CLONE_THREAD|CLONE_SETTLS|CLONE_PARENT_SETTID|CLONE_CHILD_CLEARTID|CLONE_DETACHED, [737], {entry_number:6, base_addr:0x4493ab30, limit:1048575, seg_32bit:1, contents:0, read_exec_only:0, limit_in_pages:1, seg_not_present:0, useable:1}) = 737
mmap2(NULL, 8392704, PROT_READ|PROT_WRITE|PROT_EXEC, MAP_PRIVATE|MAP_ANONYMOUS, -1, 0) = 0x4493b000
mprotect(0x4493b000, 4096, PROT_NONE)   = 0
clone(child_stack=0x4513ba90, flags=CLONE_VM|CLONE_FS|CLONE_FILES|CLONE_SIGHAND|CLONE_THREAD|CLONE_SETTLS|CLONE_PARENT_SETTID|CLONE_CHILD_CLEARTID|CLONE_DETACHED, [738], {entry_number:6, base_addr:0x4513bb30, limit:1048575, seg_32bit:1, contents:0, read_exec_only:0, limit_in_pages:1, seg_not_present:0, useable:1}) = 738
mmap2(NULL, 8392704, PROT_READ|PROT_WRITE|PROT_EXEC, MAP_PRIVATE|MAP_ANONYMOUS, -1, 0) = 0x4513c000
mprotect(0x4513c000, 4096, PROT_NONE)   = 0
clone(child_stack=0x4593ca90, flags=CLONE_VM|CLONE_FS|CLONE_FILES|CLONE_SIGHAND|CLONE_THREAD|CLONE_SETTLS|CLONE_PARENT_SETTID|CLONE_CHILD_CLEARTID|CLONE_DETACHED, [739], {entry_number:6, base_addr:0x4593cb30, limit:1048575, seg_32bit:1, contents:0, read_exec_only:0, limit_in_pages:1, seg_not_present:0, useable:1}) = 739
_exit(0)                                = ?

^ permalink raw reply	[flat|nested] 3+ messages in thread
end of thread, other threads:[~2004-05-25 18:53 UTC | newest]

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2004-05-25  2:21 Invisible threads in 2.6 lm240504
2004-05-25  7:03 ` Martin Zwickel
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2004-05-25 18:51 lm240504

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