task pdflush blocked during garbage collection.

[mike sander]

Hi All, I'm new to this list.  Hopefully i'm using a good client 
(thunderbird).  i have turned off html.

I'm working with a jffs2 filesystem on an atmel dataflash part (on 9260 
EK). 

My testing involves copying/deleting about 1000 files of a few hundred 
bytes each.  This is to simulate (on compressed timeframe) a normal 
usage pattern for our device.  My maximum data size will be about 1 MB 
within a 2MB partition.

All appears well until garbage collection starts [I think].  I have seen 
cases where during a copy operation, the copy stalls for a fairly _long_ 
duration (1 to 2 minutes) after which the copy continues to completion 
normally.    (This is not the main issue... but any suggestions on 
improving this are welcome)

Sometimes however, I get the following messages.  In this case below I 
did an "ls" in a shell prompt.  I have also seen this during a copy 
operation.  Once these messages start, the operation (cp, ls etc) never 
appears to complete.    A device reset followed by a remount shows a few 
jffs2 filesystem error (as expected).

I've seen mention of this type of behavior on the mailing list... but no 
resolution.

Vital stats:
target: at91sam9260ek
dataflash: at45db642d
environment: buildroot with linux 2.6.25 & atmel specific patches
partition: 2MB.  I started out with a clean partition using 
flash_eraseall.  Partition is specified on kernel command line.  I am 
mounting manually from shell.

The buildroot snapshot I am using is from approx May 01, although with a 
more recent 2.6.25 kernel.  I'm using mtd-utils-1.2.0 (I doubt mtd-utils 
is relevant to this issue)

I was wondering if anyone on this list might have any clues as to why 
these processes seem to be blocking.    Any suggestions on where to 
start looking and/or how to debug this are most welcome.    I can 
provide additional details as required.

Thanks in advance.

Mike


[ 5614.600000] INFO: task pdflush:49 blocked for more than 120 seconds.
[ 5614.600000] "echo 0 > /proc/sys/kernel/hung_task_timeout_secs" 
disables this message.
[ 5614.610000] pdflush       D c02b1ff8     0    49      2
[ 5614.610000] [<c02b1da0>] (schedule+0x0/0x29c) from [<c02b2218>] 
(schedule_timeout+0x20/0xc4)
[ 5614.620000] [<c02b21f8>] (schedule_timeout+0x0/0xc4) from 
[<c02b1c70>] (wait_for_common+0xf8/0x194)
[ 5614.630000]  r7:c03b3c98 r6:c03b2000 r5:c03b0cc0 r4:c03b3c58
[ 5614.640000] [<c02b1b78>] (wait_for_common+0x0/0x194) from 
[<c02b1d9c>] (wait_for_completion+0x18/0x1c)
[ 5614.650000] [<c02b1d84>] (wait_for_completion+0x0/0x1c) from 
[<c02836a8>] (spi_sync+0x58/0x6c)
[ 5614.660000] [<c0283650>] (spi_sync+0x0/0x6c) from [<c02835e4>] 
(dataflash_read+0x124/0x154)
[ 5614.670000]  r6:c03a67a4 r5:c03b3d08 r4:0098a0c4
[ 5614.670000] [<c02834c0>] (dataflash_read+0x0/0x154) from [<c02801a4>] 
(part_read+0xa0/0xd4)
[ 5614.680000] [<c0280104>] (part_read+0x0/0xd4) from [<c0237cd4>] 
(jffs2_flash_read+0x8c/0x290)
[ 5614.690000]  r7:00000000 r6:001d3344 r5:001d2200 r4:c03b3e68
[ 5614.690000] [<c0237c48>] (jffs2_flash_read+0x0/0x290) from 
[<c02341fc>] (jffs2_garbage_collect_live+0xd50/0xffc)
[ 5614.700000] [<c02334ac>] (jffs2_garbage_collect_live+0x0/0xffc) from 
[<c0234b0c>] (jffs2_garbage_collect_pass+0x664/0x784)
[ 5614.710000] [<c02344a8>] (jffs2_garbage_collect_pass+0x0/0x784) from 
[<c02391d4>] (jffs2_flush_wbuf_gc+0xc4/0x198)
[ 5614.720000] [<c0239110>] (jffs2_flush_wbuf_gc+0x0/0x198) from 
[<c0236278>] (jffs2_write_super+0x44/0x48)
[ 5614.730000]  r7:c03b3f4c r6:c0318e24 r5:00000000 r4:c0ee4200
[ 5614.740000] [<c0236234>] (jffs2_write_super+0x0/0x48) from 
[<c01e7164>] (sync_supers+0x74/0xb0)
[ 5614.750000]  r5:c0ee403c r4:c0ee4000
[ 5614.750000] [<c01e70f0>] (sync_supers+0x0/0xb0) from [<c01cef74>] 
(wb_kupdate+0x58/0x158)
[ 5614.760000]  r6:c03b3fa4 r5:c0318b20 r4:c03b3f4c
[ 5614.770000] [<c01cef1c>] (wb_kupdate+0x0/0x158) from [<c01cf680>] 
(pdflush+0x140/0x1f8)
[ 5614.770000]  r7:c032811c r6:c03b3fa4 r5:c0318b20 r4:c03b2000
[ 5614.780000] [<c01cf540>] (pdflush+0x0/0x1f8) from [<c01b4f78>] 
(kthread+0x58/0x90)
[ 5614.790000] [<c01b4f20>] (kthread+0x0/0x90) from [<c01a4934>] 
(do_exit+0x0/0x610)
[ 5614.790000]  r6:00000000 r5:00000000 r4:00000000

[ 5614.800000] INFO: task ls:27882 blocked for more than 120 seconds.
[ 5614.810000] "echo 0 > /proc/sys/kernel/hung_task_timeout_secs" 
disables this message.
[ 5614.810000] ls            D c02b1ff8     0 27882    184
[ 5614.820000] [<c02b1da0>] (schedule+0x0/0x29c) from [<c02b18e4>] 
(__down+0xf4/0x10c)
[ 5614.830000] [<c02b17f0>] (__down+0x0/0x10c) from [<c02b178c>] 
(__down_failed+0xc/0x20)
[ 5614.830000]  r8:c0049f58 r7:00000002 r6:c0049eec r5:00000000 r4:00000001
[ 5614.840000] [<c022aab4>] (jffs2_readdir+0x0/0x1bc) from [<c01f121c>] 
(vfs_readdir+0x74/0xa8)
[ 5614.850000] [<c01f11a8>] (vfs_readdir+0x0/0xa8) from [<c01f14f8>] 
(sys_getdents+0x6c/0xb8)
[ 5614.860000] [<c01f148c>] (sys_getdents+0x0/0xb8) from [<c018a960>] 
(ret_fast_syscall+0x0/0x2c)
[ 5614.870000]  r7:0000008d r6:0008b0d0 r5:0008b098 r4:0008b0b0