Re: 2.6.25-rc2-mm1 - several bugs and a crash

From: Patrick McHardy
Date: Wed Feb 20 2008 - 16:50:48 EST


Tilman Schmidt wrote:
Still, X came up fine, I could log in (Gnome feeling subjectively
a bit sluggish), call up a web page from the Internet in Firefox,
and start perusing the logs, when the whole system froze: neither
mouse nor keyboard would react anymore, and only the Wind^Wreset
button would put me back in control. After rebooting into the
previous, non-mm kernel I found this in the syslog:

Feb 20 17:22:40 xenon kernel: [ 48.180297] BUG: using smp_processor_id() in preemptible [00000000] code: ntpdate/3562
Feb 20 17:22:40 xenon kernel: [ 48.180297] caller is __nf_conntrack_find+0x9b/0xeb [nf_conntrack]
Feb 20 17:22:40 xenon kernel: [ 48.180297] Pid: 3562, comm: ntpdate Not tainted 2.6.25-rc2-mm1-testing #1
Feb 20 17:22:40 xenon kernel: [ 48.180297] [<c02015b9>] debug_smp_processor_id+0x99/0xb0
Feb 20 17:22:40 xenon kernel: [ 48.180297] [<fac643a7>] __nf_conntrack_find+0x9b/0xeb [nf_conntrack]

I guess the cause for this is a combination of preemtible
RCU and conntrack using RCU since 2.6.25-rc. Using
NF_CT_STAT_INC_ATOMIC should fix it, but I'd prefer
to have a fix that doesn't increase overhead when regular
RCU is used.

I'll see if I can find a better way to fix this tommorrow.

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