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Failing readdir() on 3.6 (was: Failing INOTIFY in 3.6.x?)

To: linux-mips@linux-mips.org
Subject: Failing readdir() on 3.6 (was: Failing INOTIFY in 3.6.x?)
From: Lluís Batlle i Rossell <viric@viric.name>
Date: Mon, 5 Nov 2012 00:21:19 +0100
In-reply-to: <20121102183828.GX2052@vicerveza.homeunix.net>
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I've investigated better the issue.

I found that, in 3.4 vs 3.6.4, the behaviour that changed is that of readdir().

Using the same userland binaries, I've run a little program in both kernels:
-------- prova.c
#include <sys/types.h>
#include <dirent.h>

int main() {
        DIR *d = opendir("/etc/init");

        if (d == NULL) {
                fprintf(stderr, "d NULL\n");
                return -1;
        }

        struct dirent *ent;
        ent = readdir(d);

        if (ent == NULL) {
                fprintf(stderr, "ent NULL\n");
                return -1;
        }
}
-----------


This program does not print anything on 3.4, but on 3.6, it prints "ent NULL".

In both cases, /etc/init is full of symlinks, like this (from a script session
in 3.6.4):
-------
S'ha iniciat l'execució de script a dl 05 nov 2012 00:16:53 CET
sh-4.2# ./prova
ent NULL
sh-4.2# ls -ld /etc/init
drwxr-xr-x 2 root root 4096  5 nov 00:12 /etc/init
sh-4.2# ls -l /etc/init
total 0
lrwxrwxrwx 1 root root 25  5 nov 00:12 atd.conf -> /etc/static/init/atd.conf
lrwxrwxrwx 1 root root 26  5 nov 00:12 boot.conf -> /etc/static/init/boot.conf
lrwxrwxrwx 1 root root 40  5 nov 00:12 control-alt-delete.conf -> 
/etc/static/init/control-alt-delete.conf
lrwxrwxrwx 1 root root 26  5 nov 00:12 cron.conf -> /etc/static/init/cron.conf
lrwxrwxrwx 1 root root 26  5 nov 00:12 dbus.conf -> /etc/static/init/dbus.conf
lrwxrwxrwx 1 root root 28  5 nov 00:12 dhcpcd.conf -> 
/etc/static/init/dhcpcd.conf
lrwxrwxrwx 1 root root 37  5 nov 00:12 emergency-shell.conf -> 
/etc/static/init/emergency-shell.conf
lrwxrwxrwx 1 root root 37  5 nov 00:12 invalidate-nscd.conf -> 
/etc/static/init/invalidate-nscd.conf
lrwxrwxrwx 1 root root 25  5 nov 00:12 kbd.conf -> /etc/static/init/kbd.conf
lrwxrwxrwx 1 root root 27  5 nov 00:12 klogd.conf -> /etc/static/init/klogd.conf
lrwxrwxrwx 1 root root 25  5 nov 00:12 lvm.conf -> /etc/static/init/lvm.conf
lrwxrwxrwx 1 root root 30  5 nov 00:12 mountall.conf -> 
/etc/static/init/mountall.conf
lrwxrwxrwx 1 root root 36  5 nov 00:12 mountall-ip-up.conf -> 
/etc/static/init/mountall-ip-up.conf
lrwxrwxrwx 1 root root 34  5 nov 00:12 mount-failed.conf -> 
/etc/static/init/mount-failed.conf
lrwxrwxrwx 1 root root 32  5 nov 00:12 networking.conf -> 
/etc/static/init/networking.conf
lrwxrwxrwx 1 root root 40  5 nov 00:12 network-interfaces.conf -> 
/etc/static/init/network-interfaces.conf
lrwxrwxrwx 1 root root 32  5 nov 00:12 nix-daemon.conf -> 
/etc/static/init/nix-daemon.conf
lrwxrwxrwx 1 root root 26  5 nov 00:12 nscd.conf -> /etc/static/init/nscd.conf
lrwxrwxrwx 1 root root 26  5 nov 00:12 ntpd.conf -> /etc/static/init/ntpd.conf
lrwxrwxrwx 1 root root 30  5 nov 00:12 runlevel.conf -> 
/etc/static/init/runlevel.conf
lrwxrwxrwx 1 root root 30  5 nov 00:12 shutdown.conf -> 
/etc/static/init/shutdown.conf
lrwxrwxrwx 1 root root 26  5 nov 00:12 sshd.conf -> /etc/static/init/sshd.conf
lrwxrwxrwx 1 root root 29  5 nov 00:12 syslogd.conf -> 
/etc/static/init/syslogd.conf
lrwxrwxrwx 1 root root 26  5 nov 00:12 tty1.conf -> /etc/static/init/tty1.conf
lrwxrwxrwx 1 root root 26  5 nov 00:12 tty2.conf -> /etc/static/init/tty2.conf
lrwxrwxrwx 1 root root 26  5 nov 00:12 tty3.conf -> /etc/static/init/tty3.conf
lrwxrwxrwx 1 root root 26  5 nov 00:12 tty4.conf -> /etc/static/init/tty4.conf
lrwxrwxrwx 1 root root 26  5 nov 00:12 tty5.conf -> /etc/static/init/tty5.conf
lrwxrwxrwx 1 root root 26  5 nov 00:12 tty6.conf -> /etc/static/init/tty6.conf
lrwxrwxrwx 1 root root 26  5 nov 00:12 udev.conf -> /etc/static/init/udev.conf
lrwxrwxrwx 1 root root 33  5 nov 00:12 udevtrigger.conf -> 
/etc/static/init/udevtrigger.conf
sh-4.2# exit

S'ha finalitzat l'execució de script a dl 05 nov 2012 00:17:22 CET
--------




On Fri, Nov 02, 2012 at 07:38:28PM +0100, Lluís Batlle i Rossell wrote:
> Hello,
> 
> updating my kernel from 3.4.2 to 3.6.4, I've noticed that upstart deadlocks at
> the very start. Stracing, I think it has to do with INOTIFY, because it
> deadlocks very early and little more has been done then.
> 
> Going 'back' to 3.4.16, makes upstart work fine. I've not tested middle 
> kernels.
> 
> I've seen this only on the fuloong minipc (mips n64), but I've done similar
> steps with the same distributions on armv5tel, i686 and x86_64, and there all
> works fine.
> 
> Does anybody know of anything broken around inotify, between 3.4 and 3.6 linux
> mips?
> 
> Any suggestion on what kernel change could have related to this, and so, get a
> clue about what middle version to test?
> 
> Regards,
> Lluís.

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