Hi all,
I have a problem running the backup software Netvault from Bakbone
(http://www.bakbone.com) under FreeBSD 4.10.
We are using Netvault to make backups of two servers and several
workstations in our network. Backups are first staged to disk and later
transferred to an ADIC FastStor 2 (LTO 1) library.
The problem occurs when the backup is transferred from disk to tape and if
the backup job spans multiple tapes (not virtual media!): Netvault
recognizes the end-of-media, loads a new media for the job and then hangs
endlessly trying to write to the new media.
Bakbone claims, that this is a problem with SysV shared memory and
semaphores in FreeBSD (and therefore not their software). Their support
also sent me a patch for Netvault (unfortunately not a binary one, so I
cannot test it) which is allegedly known to work around the problem. I
attached it below. Note the added "#if defined(PLATFORM_FREEBSD)" bits in
the code. To my understanding, the patched code polls the semaphore instead
of waiting for it.
Please also note, that I configured Netvault to use network sockets instead
of shared mem for the transfer and the problem persists (I did this by only
selecting "TCP Data Transfer" in the configure device tab for both the tape
and the virtual library and by adding [Data Channels]\nForce Sockets=TRUE
to configure.cfg as proposed by Bakbone support, for anyone familiar with
netvault). So I assume, the problem is really only related to semaphores
and not at all to shared memory(?).
I hope that someone can guess from the code if this really leads to a
deadlock because of a FreeBSD bug in SysV sempaphore handling.
I have already skimmed FreeBSD PRs for semaphore bugs, but no post really
seemed related to this specific problem (see
http://www.freebsd.org/cgi/query-pr-summary.cgi?category=&severity=&priority=&class=&state=&sort=none&text=semaphore&responsible=&multitext=&originator=&closedtoo=on&release=).
So, maybe somebody is able to make clear whether I should urge Bakbone to
fix their buggy software or look for a patch for the FreeBSD kernel and/or
libraries.
Some info on the server:
$ uname -a
FreeBSD asterix.las-cad.local 4.10-RELEASE-p3 FreeBSD 4.10-RELEASE-p3 #0:
Sat Sep 25 17:05:29 CEST 2004
[EMAIL PROTECTED]:/usr/obj/usr/src/sys/ASTERIX i386
Netvault Version 7.11 Build 10 Release R2004AUG19-CHIEF
Hardware:
AMD Athlon @ 1100 MHz, 768 MB RAM
tape library:
ahc0: port 0xbc00-0xbcff mem
0xdfffb000-0xdfffbfff irq 5 at device 12.0 on pci0
sa0 at ahc0 bus 0 target 5 lun 0
sa0: Removable Sequential Access SCSI-3 device
sa0: 80.000MB/s transfers (40.000MHz, offset 15, 16bit)
pass0 at ahc0 bus 0 target 0 lun 0
pass0: Removable Changer SCSI-2 device
pass0: 3.300MB/s transfers
staging disk:
ad4: 114473MB [232581/16/63] at ata2-master UDMA100
connected to
atapci1: port
0xc800-0xc8ff,0xcc00-0xcc03,0xd000-0xd007,0xd400-0xd403,0xd800-0xd807 irq
10 at device 10.0 on pci0
ata2: at 0xd800 on atapci1
Thank you!
Best regards,
Georg Altmann
--
---<>-<
Georg Altmann <> Phone +49 (0)89 17809328<
LAS-CAD GmbH <> Fax +49 (0)89 172594 <
Brunhildenstr. 9 <> e-mail [EMAIL PROTECTED] <
D-80639 Munich<> backup [EMAIL PROTECTED] <
Germany <> http://www.las-cad.com <
---<>-<
code:
/*
** Wait on a semaphore, i.e., wait for a resource to become available.
*/
INTERNAL DataResultE DataSemaphoreWait
(
DataChannelShmemQualifierO oShmemInfo,
int iSemNum,
BooleanT *pbBlocked,
long *plElapse
)
{
DataResultEtResult = DataFailure;
struct sembuf sOperation;
sOperation.sem_num = iSemNum;
sOperation.sem_op = -1; /* Decrement semaphore by 1 when it's ready */
sOperation.sem_flg = IPC_NOWAIT;
if (0 == semop(oShmemInfo->lSemId, &sOperation, 1))
{
TRACE((108, 0, LIBVERBOSE, "Decrement semaphore %d", iSemNum));
if(0 != (*oShmemInfo->pllEomFlag))
{
TRACE((173,0,NORMAL,"Got a EOM flag"));
tResult = DataEom;
}
else
{
tResult = DataSuccess;
}
}
else
{
long lMyError = errno;
#if defined(PLATFORM_FREEBSD)
BooleanT bDone = FALSE;
while(EAGAIN == lMyError && FALSE == bDone)
#else
if(EAGAIN == lMyError)
#endif /* Not PLATFORM_FREEBSD */
{
#if defined(PLATFORM_FREEBSD)
sOperation.sem_flg = IPC_NOWAIT;
#else
sOperation.sem_flg = 0;
#endif /* Not PLATFORM_FREEBSD */
if(NULL != plElapse
