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Description of problem:
Boot up would hang on my notebook as soon as I first tried kernel-2.6.12-1.1499_FC5, right after enabling swap partitions.  Further investigation has revealed that it was the rc.sysinit command `dmesg -s 131072 > /var/log/dmesg' that stopped the boot from making progress.

I forced an fsck of all filesystems on kernel-2.6.12-1.1492_FC5, that boots up just fine, to no avail.

I booted up 1499_FC5 with init=/bin/bash, remounted / rw and ran dmesg > /tmp/dmesg (same filesystem), and that worked.  dmesg > /var/log/dmesg, however, would still hang.  true > /var/log/dmesg wouldn't, and would successfully zero out the file.  Moving the existing /var/log/dmesg out of the way was no use either; dmesg > /var/log/dmesg would still hang.

strace /bin/dmesg completed successfully; strace /bin/dmesg > /tmp/dmesg did as well; writes were line-buffered in the first case, and in 4KiB blocks in the second, as expected.  strace /bin/dmesg > /var/log/dmesg would succeed in the first two 4KiB writes to stdout, but the third would never complete.

After the first failure, the system came back up with /dev/md8 in need of resync.  /dev/md8 is the raid 1 device holding the physical volume that contains (part of?) the logical volume containing the root filesystem.  In all other cases /dev/md8 was resyncing, and this didn't seem to affect the results.

I tried to make sure the problem was not related with sbp2 or usb-storage (I've got two external disks on which swap and raid devices are mounted), and either they're both broken, or the problem is unrelated with them.

Version-Release number of selected component (if applicable):
kernel-2.6.12-1.1499_FC5

How reproducible:
Always

Steps to Reproduce:
1.Boot up an AMD64 notebook onto 1.1499_FC5
2.After it hangs, reboot with init=/bin/bash
3.Remount / rw, then run dmesg > /var/log/dmesg
  

Actual Results:  It hangs

Expected Results:  1.1492_FC5 doesn't, and that was good :-)

Additional info: