linux-kernel - Re: mmotm 2009-08-24-16-24 uploaded

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Date:	Thu, 27 Aug 2009 18:37:26 +0900
From:	KAMEZAWA Hiroyuki <kamezawa.hiroyu@...fujitsu.com>
To:	KAMEZAWA Hiroyuki <kamezawa.hiroyu@...fujitsu.com>
Cc:	akpm@...ux-foundation.org, linux-kernel@...r.kernel.org,
	oleg@...hat.com
Subject: Re: mmotm 2009-08-24-16-24 uploaded

On Thu, 27 Aug 2009 16:05:32 +0900
KAMEZAWA Hiroyuki <kamezawa.hiroyu@...fujitsu.com> wrote:

> On Thu, 27 Aug 2009 14:44:53 +0900
> KAMEZAWA Hiroyuki <kamezawa.hiroyu@...fujitsu.com> wrote:
> 
> > 
> > In the newest mmotom, my S14nfslock hangs up. (x86-64/Fedora10)
> > 
> > On Mon, 24 Aug 2009 16:28:30 -0700
> > akpm@...ux-foundation.org wrote:
> > 
> > > ptrace-__ptrace_detach-do-__wake_up_parent-if-we-reap-the-tracee.patch
> > > do_wait-wakeup-optimization-shift-security_task_wait-from-eligible_child-to-wait_consider_task.patch
> > 
> > bisected. following 2 patches for filtering SIGCHLD cause hang (for my environ).
> > 
> > > do_wait-wakeup-optimization-change-__wake_up_parent-to-use-filtered-wakeup.patch
> > > do_wait-wakeup-optimization-change-__wake_up_parent-to-use-filtered-wakeup-selinux_bprm_committed_creds-use-__wake_up_parent.patch
> 
> removed S14nfslockd from rc5.d and check it by strace
> ==
>  2712] fstat(6, {st_mode=S_IFREG|0644, st_size=0, ...}) = 0
> [pid  2712] mmap(NULL, 4096, PROT_READ|PROT_WRITE, MAP_PRIVATE|MAP_ANONYMOUS, -1, 0) = 0x7fc6f263c000
> [pid  2712] dup(6)                      = 7
> [pid  2712] write(6, "2712\n"..., 5)    = 5
> [pid  2712] close(6)                    = 0
> [pid  2712] munmap(0x7fc6f263c000, 4096) = 0
> [pid  2712] clone(Process 2713 attached
> child_stack=0, flags=CLONE_CHILD_CLEARTID|CLONE_CHILD_SETTID|SIGCHLD, child_tidptr=0x7fc6f2625780) = 2713
> [pid  2712] wait4(2713, Process 2712 suspended
>  <unfinished ...>
> ==
> When process 2713 exits, process 2712 don't wake up.
> 
> Then, I sent SIGTERM to 2712
> ==
> Process 2713 detached
> 
> [pid  2712] <... wait4 resumed> NULL, 0, NULL) = -1 ECHILD (No child processes)
> [pid  2712] --- SIGTERM (Terminated) @ 0 (0) ---
> ==
> 
(Moved onto mmotm-Aug-27)
Added printk as...

==
@@ -1571,6 +1571,10 @@ static int child_wait_callback(wait_queu
                                                child_wait);
        struct task_struct *p = key;
...
+       printk("pid %d ppid %d exit_signal %d wo_flags %lx private %p parent %p\n",
+               p->pid, p->parent->pid, p->exit_signal, wo->wo_flags,
+               wait->private, p->parent);
+
==
Then,

== strace
[pid  2989] clone(Process 2990 attached
child_stack=0, flags=CLONE_CHILD_CLEARTID|CLONE_CHILD_SETTID|SIGCHLD, child_tidptr=0x7faf6f4a2780) = 2990
[pid  2989] wait4(2990, Process 2989 suspended
 <unfinished ...>
[pid  2990] exit_group(0)               = ?
Process 2989 resumed
Process 2990 detached
== printk
Aug 27 18:48:05 localhost kernel: [ 1312.328933] pid 2990 ppid 2978 exit_signal 17 wo_flags 40000004 private ffff8806139b5040 parent ffff8806139b5040
Aug 27 18:48:05 localhost kernel: [ 1312.329300] pid 2990 ppid 2989 exit_signal -1 wo_flags 4 private ffff8806139ba820 parent ffff8806139ba820
==
(2978 is strace)
The patch itself works as expected.

Maybe something bad with kernel or rpc.statd, is around p->exit_signal.
(Without strace, p->exit_signal was -1. no difference)

Thanks,
-Kame






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