Description of problem:
AFAIK dmesg defaults to a small buffer. Since you increase the LOG_BUF_LEN
in kernel, it may be good to use
dmesg -s <big_buf> > /var/log/dmesg
in rc.sysinit (I think big_buf should be >= 65536)
How reproducible/Steps to Reproduce:
On this system I haven't any driver that can trigger the problem, so I
just tried to fill the dmesg buffer after boot to confirm that dmesg still
needs '-s <buf>' to get all the available info.
I have this problem on a rh6x system with 8 software raid1 partitions and
applied the fix suggested above.
Will be fixed in 6.12-1.