I suspect that I have a problem with lock/mutex contention.
Reading from a USB disk appears to lock out the firewire driver
for too long, causing data transfer (writing to firewire bus) to fail
with EAGAIN.  Once it fails it does not recover.

kernel: fwohci1: IT DMA underrun (0x40308011) (stat & OHCI_CNTL_CYCMATCH_S)
last message repeated 63 times
This is from the end of the fwohci_itxbuf_enable() function in dev/firewire/fwohci.c

I added LOCK_PROFILING to the kernel and gathered some data.
The data is quite verbose, so I sorted by "max" and am including
the first 40 lines.  This is a true real-time task, so I am concerned
with the worst case rather than the average.

First, data from approx 20 seconds without a problem:

debug.lock.prof.enable: 0
debug.lock.prof.reset: 0
debug.lock.prof.stats:
max wait_max total wait_total count avg wait_avg cnt_hold cnt_lock name 16990 0 2216486 0 1837 1206 0 0 0 /usr/src/sys/kern/vfs_vnops.c:533 (lockmgr:ufs) 5852 0 11669 0 18 648 0 0 0 /usr/src/sys/kern/vfs_subr.c:1693 (lockmgr:syncer) 1659 0 5522 0 34 162 0 0 0 /usr/src/sys/kern/vfs_mount.c:2231 (sleep mutex:struct mount mtx) 1540 0 30353 0 15283 1 0 0 0 /usr/src/sys/kern/sys_pipe.c:574 (sleep mutex:pipe mutex) 1415 0 1885651 0 53865 35 0 0 0 /usr/src/sys/vm/vm_map.c:3526 (sx:user map) 1385 0 252414 0 53865 4 0 0 0 /usr/src/sys/vm/vm_fault.c:937 (sleep mutex:vm object) 1361 0 84475 0 53865 1 0 0 0 /usr/src/sys/vm/vm_fault.c:938 (sleep mutex:vm page queue mutex) 1044 0 2079 0 2 1039 0 0 0 /usr/src/sys/kern/vfs_mount.c:2194 (sleep mutex:struct mount mtx) 934 0 65031 0 146 445 0 0 0 /usr/src/sys/vm/vm_pager.c:311 (lockmgr:bufwait) 864 0 194008 0 53865 3 0 0 0 /usr/src/sys/amd64/amd64/pmap.c:2958 (sleep mutex:pmap) 864 0 192948 0 53865 3 0 0 0 /usr/src/sys/amd64/amd64/pmap.c:2957 (sleep mutex:vm page queue mutex) 862 0 24690 0 30 823 0 0 0 /usr/src/sys/kern/kern_mutex.c:147 (sleep mutex:nfe0) 857 0 84478 0 53863 1 0 0 0 /usr/src/sys/amd64/amd64/trap.c:740 (sleep mutex:process lock) 697 0 154340 0 3292 46 0 0 0 /usr/src/sys/kern/vfs_bio.c:2559 (lockmgr:bufwait) 557 0 896107 0 13438 66 0 0 0 /usr/src/sys/kern/vfs_bio.c:1835 (lockmgr:bufwait) 519 0 1615 0 11 146 0 0 0 /usr/src/sys/ufs/ffs/ffs_vfsops.c:1321 (sleep mutex:struct mount mtx) 481 0 24417 0 13438 1 0 0 0 /usr/src/sys/kern/vfs_subr.c:1595 (sleep mutex:bufobj interlock) 367 0 65371 0 9178 7 0 0 0 /usr/src/sys/kern/sys_pipe.c:643 (sleep mutex:pipe mutex) 351 0 2324 0 52 44 0 0 0 /usr/src/sys/kern/vfs_subr.c:2083 (lockmgr:ufs) 333 0 325772 0 53865 6 0 0 0 /usr/src/sys/vm/vm_fault.c:297 (sleep mutex:vm object) 329 0 171709 0 108608 1 0 0 0 /usr/src/sys/amd64/amd64/pmap.c:3989 (sleep mutex:pmap) 329 0 2090 0 534 3 0 0 0 /usr/src/sys/kern/vfs_subr.c:337 (sleep mutex:struct mount mtx) 327 0 99170 0 58917 1 0 0 0 /usr/src/sys/vm/vm_page.c:1052 (sleep mutex:vm page queue free mutex) 305 0 514 0 4 128 0 0 0 /usr/src/sys/vm/vm_object.c:541 (sleep mutex:vm object) 304 0 304 0 1 304 0 0 0 /usr/src/sys/vm/uma_core.c:1565 (sleep mutex:UMA lock) 297 0 359 0 13 27 0 0 0 /usr/src/sys/kern/vfs_bio.c:3611 (sleep mutex:vm object) 296 0 23341 0 983 23 0 0 0 /usr/src/sys/kern/tty_ttydisc.c:467 (sleep mutex:ttymtx) 291 0 448 0 6 74 0 0 0 /usr/src/sys/vm/vm_object.c:1719 (sleep mutex:vm object) 284 0 12090 0 997 12 0 0 0 /usr/src/sys/kern/sys_generic.c:1446 (sleep mutex:select mtxpool) 281 0 8752 0 955 9 0 0 0 /usr/src/sys/kern/sys_generic.c:1455 (sleep mutex:sellck) 265 0 796 0 3 265 0 0 0 /usr/src/sys/vm/vm_glue.c:738 (sx:allproc) 251 74 26825 74 16746 1 0 0 1 /usr/src/sys/kern/vfs_bio.c:1488 (sleep mutex:buf queue lock) 231 0 7470 0 2848 2 0 0 0 /usr/src/sys/geom/geom_io.c:77 (sleep mutex:bio queue) 228 0 228 0 1 228 0 0 0 /usr/src/sys/vm/vm_map.c:2973 (sx:user map) 227 0 543 0 5 108 0 0 0 /usr/src/sys/kern/vfs_subr.c:1693 (lockmgr:devfs) 215 0 840 0 13 64 0 0 0 /usr/src/sys/dev/random/yarrow.c:191 (sleep mutex:random reseed) 202 0 198454 0 13438 14 0 0 0 /usr/src/sys/kern/vfs_bio.c:2963 (sleep mutex:vm object) 199 0 18282 0 3668 4 0 0 0 /usr/src/sys/kern/sys_pipe.c:611 (sleep mutex:pipe mutex) 190 0 1606 0 800 2 0 0 0 /usr/src/sys/kern/vfs_bio.c:3089 (sleep mutex:sleep mtxpool) 189 0 83829 0 53899 1 0 0 0 /usr/src/sys/vm/vm_object.c:482 (sleep mutex:vm object)
debug.lock.prof.rejected: 0
debug.lock.prof.skipcount: 0
debug.lock.prof.skipspin: 0



Next, data when the problem occurs:

debug.lock.prof.enable: 0
debug.lock.prof.reset: 0
debug.lock.prof.stats:
max wait_max total wait_total count avg wait_avg cnt_hold cnt_lock name 1586932 0 10264893 0 2290 4482 0 0 0 /usr/src/sys/kern/vfs_vnops.c:533 (lockmgr:ufs) 35676 0 165709 0 20 8285 0 0 0 /usr/src/sys/ufs/ffs/ffs_vfsops.c:1465 (lockmgr:ufs) 32133 0 80040 0 17541 4 0 0 0 /usr/src/sys/vm/vm_object.c:482 (sleep mutex:vm object) 32129 0 50459 0 276 182 0 0 0 /usr/src/sys/vm/vm_object.c:720 (sleep mutex:vm page queue mutex) 30899 0 47896 0 2 23948 0 0 0 /usr/src/sys/kern/vfs_syscalls.c:3508 (lockmgr:ufs) 30680 0 36901 0 17 2170 0 0 0 /usr/src/sys/kern/imgact_elf.c:774 (lockmgr:ufs) 26779 0 912921 0 9351 97 0 0 0 /usr/src/sys/kern/vfs_bio.c:1835 (lockmgr:bufwait) 25691 0 193858 0 1850 104 0 0 0 /usr/src/sys/kern/vfs_subr.c:2083 (lockmgr:ufs) 25596 0 592159 0 1205 491 0 0 0 /usr/src/sys/vm/vm_pager.c:311 (lockmgr:bufwait) 24791 0 95678 0 24 3986 0 0 0 /usr/src/sys/kern/kern_sysctl.c:1513 (sx:sysctl mem) 24788 0 250975 0 10563 23 0 0 0 /usr/src/sys/kern/kern_sysctl.c:1521 (sx:sysctl lock) 23977 0 68951 0 538 128 0 0 0 /usr/src/sys/geom/geom_event.c:185 (sx:GEOM topology) 20302 0 112442 0 6539 17 0 0 0 /usr/src/sys/kern/kern_sysctl.c:1417 (sleep mutex:Giant) 18552 0 18552 0 1 18552 0 0 0 /usr/src/sys/kern/kern_descrip.c:2586 (sx:allproc) 17688 0 17917 0 150 119 0 0 0 /usr/src/sys/kern/kern_descrip.c:1580 (sleep mutex:fdesc) 14813 0 1285697 0 15257 84 0 0 0 /usr/src/sys/kern/vfs_bio.c:2559 (lockmgr:bufwait) 5904 0 16455 0 34 483 0 0 0 /usr/src/sys/kern/vfs_subr.c:1693 (lockmgr:syncer) 5715 0 6088 0 8 761 0 0 0 /usr/src/sys/kern/vfs_vnops.c:604 (lockmgr:ufs) 5464 0 5464 0 1 5464 0 0 0 /usr/src/sys/ufs/ufs/ufs_dirhash.c:216 (sx:dirhash) 4690 0 9137 0 2 4568 0 0 0 /usr/src/sys/vm/vm_meter.c:113 (sleep mutex:vm object_list) 3304 0 18601 0 6 3100 0 0 0 /usr/src/sys/kern/kern_proc.c:1079 (sx:allproc) 3041 0 5969 0 2 2984 0 0 0 /usr/src/sys/vm/vm_meter.c:130 (sx:allproc) 2964 0 35694 0 127 281 0 0 0 /usr/src/sys/vm/vm_map.c:2766 (sleep mutex:system map) 2474 0 28012 0 127 220 0 0 0 /usr/src/sys/vm/vm_kern.c:289 (sleep mutex:system map) 2362 0 4716 0 2 2358 0 0 0 /usr/src/sys/kern/kern_malloc.c:777 (sleep mutex:malloc) 2343 0 8922 0 64 139 0 0 0 /usr/src/sys/kern/vfs_mount.c:2231 (sleep mutex:struct mount mtx) 1813 0 3021 0 2 1510 0 0 0 /usr/src/sys/kern/kern_linker.c:2122 (sx:kernel linker) 1588 0 622646 0 16428 37 0 0 0 /usr/src/sys/vm/vm_map.c:3526 (sx:user map) 1544 0 4025 0 15 268 0 0 0 /usr/src/sys/vm/vm_map.c:2139 (sx:user map) 1537 0 4331 0 47 92 0 0 0 /usr/src/sys/vm/vm_map.c:2766 (sx:user map) 1529 0 3991 0 437 9 0 0 0 /usr/src/sys/vm/vm_fault.c:1017 (sleep mutex:vm object) 1501 0 16994 0 127 133 0 0 0 /usr/src/sys/vm/vm_kern.c:394 (sleep mutex:vm object) 1138 0 44043 0 53 831 0 0 0 /usr/src/sys/kern/kern_mutex.c:147 (sleep mutex:nfe0) 1061 0 142103 0 9351 15 0 0 0 /usr/src/sys/kern/vfs_bio.c:2963 (sleep mutex:vm object) 1046 0 99060 0 59009 1 0 0 0 /usr/src/sys/vm/vm_page.c:1052 (sleep mutex:vm page queue free mutex) 1032 0 2640 0 18 146 0 0 0 /usr/src/sys/ufs/ffs/ffs_vfsops.c:1321 (sleep mutex:struct mount mtx) 974 0 57222 0 34916 1 0 0 0 /usr/src/sys/amd64/amd64/pmap.c:3989 (sleep mutex:pmap) 964 0 3167 0 1203 2 0 0 0 /usr/src/sys/kern/tty_pts.c:126 (sleep mutex:ttymtx) 952 0 9113 0 127 71 0 0 0 /usr/src/sys/vm/vm_kern.c:325 (sleep mutex:vm object) 892 0 79906 0 16428 4 0 0 0 /usr/src/sys/vm/vm_fault.c:937 (sleep mutex:vm object)
debug.lock.prof.rejected: 0
debug.lock.prof.skipcount: 0
debug.lock.prof.skipspin: 0



If I understand this, something was locked out for 1.58 seconds?  YIKES!


grep -i giant /var/run/dmesg.boot
atkbd0: [GIANT-LOCKED]

So the only thing still using the giant lock is the keyboard?
I only use this keyboard with the firmware. I rsh in from another machine.


FreeBSD 8.0
amd64
nforce4-ultra chipset  (USB controller)
NEC firewire controller on PCI card

fwohci1: <NEC uPD72871/2> mem 0xfdeff000-0xfdefffff irq 19 at device 8.0 on pci2
fwohci1: [ITHREAD]
fwohci1: OHCI version 1.0 (ROM=1)
fwohci1: No. of Isochronous channels is 4.
fwohci1: Phy 1394a available S400, 2 ports.
fwohci1: max_rec 1024 -> 2048
firewire1: <IEEE1394(FireWire) bus> on fwohci1
dcons_crom1: <dcons configuration ROM> on firewire1
dcons_crom1: bus_addr 0x7c31c000
dcons_crom1: dcons_paddr is already set

ehci0: <NVIDIA nForce4 USB 2.0 controller> mem 0xfebfe000-0xfebfe0ff irq 22 at device 2.1 on pci0
ehci0: [ITHREAD]
usbus1: EHCI version 1.0 addr 0x61 on iicbus1
usbus1: <NVIDIA nForce4 USB 2.0 controller> on ehci0

usbd_set_config_index:523: could not read device status: USB_ERR_SHORT_XFER
ugen1.2: <JMicron> at usbus1
umass0: <MSC Bulk-Only Transfer> on usbus1
umass0:  SCSI over Bulk-Only; quirks = 0x0000
umass0:6:0:-1: Attached to scbus6
da0 at umass-sim0 bus 0 target 0 lun 0
da0: <Hitachi HDS722020ALA330 > Fixed Direct Access SCSI-2 device
da0: 40.000MB/s transfers
da0: 1907729MB (3907029168 512 byte sectors: 255H 63S/T 243201C)


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