[Galaxy Note GT-N7000 General] samarium:
/system stubbonly RO

I tried mount -o remount,rw /system like I would normally do, and it failed.

# mount|grep system
/dev/block/mmcblk0p9 /system ext4 ro,relatime,barrier=1,data=ordered 0 0
# strace -e mount mount -o remount,rw /system
syscall_983045(0xb0012c7c, 0xb00144c4, 0xffffffc8, 0, 0, 0xb00094f0, 0xbe8c1bd0, 0xf0005, 0xb0012c7c, 0, 0, 0, 0, 0xbe8c1b80, 0xb00045fb, 0xb0001200, 0x10, 0xb0012c7c, 0xb671, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0) = 0
syscall_983045(0x400cc4c4, 0x400cc488, 0x400cc5c0, 0x40, 0x400cc488, 0xbe8c1bd0, 0xbe8c1be8, 0xf0005, 0xbe8a2000, 0x400c2000, 0x50000, 0x4007d000, 0, 0xbe8c1590, 0x400a4a59, 0x4008a480, 0x600f0010, 0x400cc4c4, 0xb671, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0) = 0
mount("/dev/block/mmcblk0p9", "/system", 0x17af0, MS_REMOUNT|MS_VERBOSE, 0) = -1 EROFS (Read-only file system)
mount: Read-only file system
# strace -e mount /system/xbin/mount -o remount,rw /system
syscall_983045(0xb0012c7c, 0xb00144c4, 0xffffffc8, 0, 0, 0xb00094f0, 0xbeb46bd0, 0xf0005, 0xb0012c7c, 0, 0, 0, 0, 0xbeb46b80, 0xb00045fb, 0xb0001200, 0x10, 0xb0012c7c, 0xb671, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0) = 0
syscall_983045(0x4010a4c4, 0x4010a488, 0x4010a5c0, 0x40, 0x4010a488, 0xbeb46bd0, 0xbeb46be8, 0xf0005, 0xbeb27000, 0x40100000, 0x50000, 0x400bb000, 0, 0xbeb46840, 0x400e2a59, 0x400c8480, 0x60070010, 0x4010a4c4, 0xb671, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0) = 0
mount("/dev/block/mmcblk0p9", "/system", 0x7e593, MS_REMOUNT|MS_VERBOSE|0x200000, 0x1f7a450) = -1 EROFS (Read-only file system)
mount("/dev/block/mmcblk0p9", "/system", 0x7e593, MS_RDONLY|MS_REMOUNT|MS_VERBOSE|0x200000, 0x1f7a450) = 0
# mount|grep system
/dev/block/mmcblk0p9 /system ext4 ro,relatime,barrier=1,data=ordered 0 0
# cat /proc/cmdline
loglevel=4 console=ram sec_debug.enable=0 sec_debug.enable_user=0 c1_watchdog.sec_pet=5 sec_log=0x100000@0x5ea00000 s3cfb.bootloaderfb=0x5ec00000 lcdtype=3 consoleblank=0 lpj=3981312 vmalloc=144m
# cat /proc/version
Linux version 3.0.30-CM-g8e5edb1 (xplodwild@barbecue) (gcc version 4.4.3 (GCC) ) #1 SMP PREEMPT Thu May 3 18:36:36 CEST 2012
#

I tried rebooting into CWM, and reinstalling cm9 build#3, and it crashed 120 seconds after it tried to unmount /system. I was connected via adb shell and saw the umount process in D state, then the watchdog fired and device rebooted, dumping last_kmsg, enclosed fully below, but relevent excerpt is here:

<3>[ 240.205187] INFO: task jbd2/mmcblk0p9-:1869 blocked for more than 120 seconds.
<3>[ 240.205293] "echo 0 > /proc/sys/kernel/hung_task_timeout_secs" disables this message.
<6>[ 240.205402] jbd2/mmcblk0p9- D c088da20 0 1869 2 0x00000000
<4>[ 240.205510] Backtrace:
<4>[ 240.205596] [<c088d264>] (__schedule+0x0/0x898) from [<c088dd0c>] (schedule+0x80/0x84)
<4>[ 240.205733] [<c088dc8c>] (schedule+0x0/0x84) from [<c04bc3d4>] (jbd2_journal_commit_transaction+0x258/0x1550)
<4>[ 240.205893] [<c04bc17c>] (jbd2_journal_commit_transaction+0x0/0x1550) from [<c04c2b84>] (kjournald2+0xc0/0x218)
<4>[ 240.206048] [<c04c2ac4>] (kjournald2+0x0/0x218) from [<c0395b58>] (kthread+0x94/0x9c)
<4>[ 240.206181] [<c0395ac4>] (kthread+0x0/0x9c) from [<c0378af0>] (do_exit+0x0/0x6f8)
<4>[ 240.206283] r7:00000013 r6:c0378af0 r5:c0395ac4 r4:e0885cac
<0>[ 240.206393] Kernel panic - not syncing: hung_task: blocked tasks
<4>[ 240.206476] Backtrace:
<4>[ 240.206546] [<c0339dd4>] (dump_backtrace+0x0/0x118) from [<c088caf4>] (dump_stack+0x20/0x24)
<4>[ 240.206664] r7:e0b063e0 r6:c0a937b8 r5:c0ab5e6c r4:c0b68b08
<4>[ 240.206774] [<c088cad4>] (dump_stack+0x0/0x24) from [<c088cb7c>] (panic+0x84/0x1b0)
<4>[ 240.206905] [<c088caf8>] (panic+0x0/0x1b0) from [<c03bdd14>] (watchdog+0x1f4/0x258)
<4>[ 240.207009] r3:00000001 r2:013cc000 r1:00000000 r0:c09e73bd
<4>[ 240.207120] [<c03bdb20>] (watchdog+0x0/0x258) from [<c0395b58>] (kthread+0x94/0x9c)
<4>[ 240.207240] [<c0395ac4>] (kthread+0x0/0x9c) from [<c0378af0>] (do_exit+0x0/0x6f8)
<4>[ 240.207342] r7:00000013 r6:c0378af0 r5:c0395ac4 r4:e0885f14
<0>[ 240.207555] Rebooting in 1 seconds..

This is reproducible for me, although I'm guessing not for you.

History of this device:

Stock XXLA6.

Heimdall XXLC1 prerooted

Heimdall CF-root zImage

CWM nandroid GB

CWM install cm9build3

Not sure if could mount -o remount,rw /system at this point.

CWM nandroid ICS

CWM restore GB looking for adb devices serial#, confirmed ok on GB.

CWM restore ICS, confirmed serial # still broken.

Found mount -o remount,rw /system failed.

Tried to unmount in CWM, kernel panic happens.

Tried to reflash cm9build3 in CWM, kernel panic happens.

I'm considering where to go from here, heimdall XXLC1 + CF-root and start again?