netdev - Re: [PATCH] tcp FRTO: in-order-only "TCP proxy" fragility workaround (fwd)

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Message-ID: <48f9251b.1626360a.6574.61ec@mx.google.com>
Date:	Fri, 17 Oct 2008 20:51:49 -0300
From:	Dâniel Fraga <fragabr@...il.com>
To:	"Ilpo Järvinen" <ilpo.jarvinen@...sinki.fi>
Cc:	Thomas Gleixner <tglx@...utronix.de>,
	David Miller <davem@...emloft.net>,
	Netdev <netdev@...r.kernel.org>
Subject: Re: [PATCH] tcp FRTO: in-order-only "TCP proxy" fragility
 workaround (fwd)

On Mon, 13 Oct 2008 16:35:08 +0300 (EEST)
"Ilpo Järvinen" <ilpo.jarvinen@...sinki.fi> wrote:

	Just reporting another stall event... Who knows it helps in some way...

> ...might turn out related. It has somewhat similar problem though 
> different syscall. Not enough info on what kernel version etc. 
> there though.

	Well, I can be wrong, but I think those stalls are related to USB (or USB helped to 
"solve" the stall temporarily)... I explain below (I have a monitor with usb hub connected):

Oct 17 19:35:55 tux sudo: pam_unix(sudo:session): session opened for user root by fraga(uid=0)
Oct 17 19:35:55 tux sudo: pam_unix(sudo:session): session closed for user root

	^---------- sudo opened the session at 19:35

Oct 17 19:38:16 tux sudo:    fraga : TTY=pts/2 ; PWD=/usr/local/lib ; USER=root ; COMMAND=/usr/local/bin/rm libdvdread.a libdvdread.la libdvdread.so libdvdread.so.3 libdvdread.so.3.2.1 libdvdread.so.4 libdvdread
.so.4.1.2

	^---------- I tried to run this command with sudo. And it stalled. Notice that it was logged only on 19:38.

Oct 17 19:38:16 tux sudo: pam_unix(sudo:session): session opened for user root by fraga(uid=0)
Oct 17 19:38:16 tux sudo: pam_unix(sudo:session): session closed for user root
Oct 17 19:40:20 tux vmunix: ci000/000:21ub/-/-./-../-..:./nu/nu7

	^----------- Here is the stall. You can see that the log is corrupted, every other line.

Oct 17 19:40:20 tux vmunix: 6ipt S I 11 os Lgtc pia S os]o s-000:21112

	^----------- Every other line. Here is when I turned off my monitor with USB... Unless it was an extreme coincidence, I'm sure this event
of turning off and...

Oct 17 19:40:25 tux vmunix: sd 9:0:0:0: [sdb] Attached SCSI removable disk
Oct 17 19:40:25 tux scsi.agent[5498]: disk at /devices/pci0000:00/0000:00:02.1/usb2/2-1/2-1.1/2-1.1.1/2-1.1.1:1.0/host9/target9:0:0/9:0:0:0

	^---------- ...turning on again, helped to "solve" the stall. The stall ended when I turned off the monitor.

Oct 17 19:40:28 tux sudo:    fraga : TTY=pts/2 ; PWD=/usr/local/lib ; USER=root ; COMMAND=/usr/local/bin/ls
Oct 17 19:40:28 tux sudo: pam_unix(sudo:session): session opened for user root by fraga(uid=0)
Oct 17 19:40:28 tux sudo: pam_unix(sudo:session): session closed for user root
Oct 17 19:40:30 tux scsi.agent[5310]: Attribute /sys/devices/pci0000:00/0000:00:02.1/usb2/2-1/2-1.1/2-1.1.1/2-1.1.1:1.0/host9/type does not exist
Oct 17 19:40:35 tux scsi.agent[5493]: Attribute /sys/devices/pci0000:00/0000:00:02.1/usb2/2-1/2-1.1/2-1.1.1/2-1.1.1:1.0/host9/target9:0:0/type does not exist
Oct 17 20:12:37 tux vmunix: usb-storage: device found at 14
Oct 17 20:12:37 tux vmunix: usb-storage: waiting for device to settle before scanning
Oct 17 20:12:42 tux vmunix: scsi 10:0:0:0: Direct-Access     Generic  ls SC   53 Q  NI 
Oct 17 20:12:42 tux vmunix: k
Oct 17 20:12:42 tux scsi.agent[7439]: disk at /devices/pci0000:00/0000:00:02.1/usb2/2-1/2-1.1/2-1.1.1/2-1.1.1:1.0/host10/target10:0:0/10:0:0:0
Oct 17 20:12:47 tux vmunix: DROP INPUT: IN=eth0 OUT= MAC=ff:ff:ff:ff:ff:ff:00:15:e9:e2:00:db:08:00 SRC=192.168.0.1 DST=255.255.255.255 LEN=334 TOS=0x00 PREC=0x00 TTL=64 ID=6668 PROTO=UDP SPT=67 DPT=68 LEN=314 
Oct 17 20:12:47 tux scsi.agent[7252]: Attribute /sys/devices/pci0000:00/0000:00:02.1/usb2/2-1/2-1.1/2-1.1.1/2-1.1.1:1.0/host10/type does not exist
Oct 17 20:12:53 tux scsi.agent[7435]: Attribute /sys/devices/pci0000:00/0000:00:02.1/usb2/2-1/2-1.1/2-1.1.1/2-1.1.1:1.0/host10/target10:0:0/type does not exist

	***
	
	At the server I have an usb device connected too...

	OR at eh end it's just a symptom of the problem... I don't
know. The interesting thing is that as soon as I turned off the monitor 
(at the exact moment), the speaker beeped, because I used TAB to auto
complete my command, and I knew that sudo wasn't stalled
anymore.

	Maybe what the kernel does when we remove a usb hub could give us a hint about the stalling issue...

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