[Samba] "Oplock" error messages with samba on Linux

[jra at dp.samba.org]

On Thu, Mar 13, 2003 at 01:40:03PM -0600, Amit_Bhutani at Dell.com wrote:
> TEST: 
> =====
> SAMBA STRESS OVER GIGABIT NETWORK: This is a simple
> Read/Write/Compare/Delete kind of test over the network via Samba. Multiple
> clients with multiple threads try to read/write/compare/delete(in a loop) a
> finite sized file (64K block size) over samba for a prolonged period of time
> in an effort to stress test the server. 
> 
> SERVER SIDE CONFIG:
> ===================
> ARCH: x86 
> OS: RHL AS 2.1 
> KERNEL: 2.4.9-e.3smp
> SAMBA: 2.2.7-1.21as.i386.rpm (also tried RH AS2.1 stock version:
> 2.2.1a-4.i386.rpm)
> NIC: 2 ONBOARD GIG BCM5703(COPPER)ON A STATIC GEC TRUNK
> RAM: 512 MB 
> CPU: Dual 2.66GHz CPU with HT ON (tried several different speed CPU's: 2.2,
> 2.4, 3.06 etc)
> SWAP: 2 GB
> SCSI/RAID: Able to reproduce this on SCSI as well as RAID 0 (not tried other
> RAID configs)
> 
> CLIENT SIDE CONFIG:
> ===================
> SAMBA CLIENTS: Windows only (tried both NT4 and W2K). Please note that there
> are *no* Linux clients trying to access the samba share. The clients are all
> Windows and are all installed from one common image.
> 
> DESCRIPTION OF FAILURES:
> ========================
> The Stress Test Controller starts to show some Read/Write/Compare failures
> anywhere from a 30 mins up to a 24 hour period into the test. These failures
> continue to occur and eventually the server "locks up". Tried to enable
> "nmi_watchdog" with serial console. No OOPS capture yet. I also tried
> raising the samba debug level (went up to 3) , printk level raised to "7 4 1
> 7", SysRq enabled etc. None of the information I have captured so far gives
> me any definite theory on why this is happening. What I do notice is that in
> almost all the failures, the samba logs have references to "oplocks". Any
> body has any ideas why this could be happening ? Any ideas for what I can do
> further to troubleshoot. I have tried various other things that I have not
> posted with this message to try and keep this post readable. Posted below
> are a sample smbd.log, <samba_client_name>.log and my smb.conf file from one
> of the recent failures. Any suggestions would be helpful.

Server 'locks up' represents a Linux kernel bug. No other option.
Samba as a user level process should not be able to cause the
kernel to freeze.

On a 'perfect' network (no lost packets) oplock break failures are due to
bugs in Windows clients not responding to asynchronous 'break' messages
sent back to them over a TCP stream. What *exact* config are the Windows
clients ? What service pack ?

Jeremy Allison,
Samba Team.