Re: Seeing "huh, entered softirq 8 ffffffff802682aa preempt_count00000100, exited with 00010100?" in tip.git

From: Jeremy Fitzhardinge
Date: Thu Jan 29 2009 - 20:44:56 EST

Paul E. McKenney wrote:
On Thu, Jan 29, 2009 at 02:12:31PM -0800, Jeremy Fitzhardinge wrote:
When I boot my x86-64 tip.git kernel under Xen, I'm seeing:

pnp: PnP ACPI: disabled
NET: Registered protocol family 2
huh, entered softirq 8 ffffffff802682aa preempt_count 00000100, exited with 00010100?
IP route cache hash table entries: 512 (order: 0, 4096 bytes)
TCP established hash table entries: 1024 (order: 2, 16384 bytes)
XENBUS: Device with no driver: device/console/0
Freeing unused kernel memory: 372k freed
Red Hat nash version 6.0.19 starting
Mounting proc filesystem
Mounting sysfs filesystem
Creating /dev
BUG: scheduling while atomic: swapper/0/0x00010000
Modules linked in:
Pid: 0, comm: swapper Not tainted 2.6.29-rc3-tip #481
Call Trace:
[<ffffffff80238c1f>] __schedule_bug+0x62/0x66
[<ffffffff80211d2d>] ? retint_restore_args+0x5/0x20
[<ffffffff80503921>] __schedule+0x95/0x792
[<ffffffff802093aa>] ? _stext+0x3aa/0x1000
[<ffffffff802093aa>] ? _stext+0x3aa/0x1000
[<ffffffff805040c2>] schedule+0xe/0x22
[<ffffffff8020ff04>] cpu_idle+0x70/0x72
[<ffffffff804fc3a0>] cpu_bringup_and_idle+0x13/0x15
Creating initial device nodes
Setting up hotplug.

From what I can see, softirq 8 is the RCU softirq. I don't know if the "scheduling while atomic" is related or not, but its two new schedulerish symptoms appearing at once, so I think its likely they're related.

Hmmm... Mysterious, as you seem to be using classic RCU, which hasn't
changed in awhile. Which branch of the tip tree are you using?

tip/master. It looks like this appeared since -rc1. Mu current suspicion is the percpu changes, since I'm seeing some other strange symptoms.

To unsubscribe from this list: send the line "unsubscribe linux-kernel" in
the body of a message to majordomo@xxxxxxxxxxxxxxx
More majordomo info at
Please read the FAQ at