mirror of
https://github.com/torvalds/linux
synced 2024-11-05 18:23:50 +00:00
No description
f186ce61bb
It looks like this:
Message from syslogd@flamingo at Apr 26 00:45:00 ...
kernel:unregister_netdevice: waiting for lo to become free. Usage count = 4
They seem to coincide with net namespace teardown.
The message is emitted by netdev_wait_allrefs().
Forced a kdump in netdev_run_todo, but found that the refcount on the lo
device was already 0 at the time we got to the panic.
Used bcc to check the blocking in netdev_run_todo. The only places
where we're off cpu there are in the rcu_barrier() and msleep() calls.
That behavior is expected. The msleep time coincides with the amount of
time we spend waiting for the refcount to reach zero; the rcu_barrier()
wait times are not excessive.
After looking through the list of callbacks that the netdevice notifiers
invoke in this path, it appears that the dst_dev_event is the most
interesting. The dst_ifdown path places a hold on the loopback_dev as
part of releasing the dev associated with the original dst cache entry.
Most of our notifier callbacks are straight-forward, but this one a)
looks complex, and b) places a hold on the network interface in
question.
I constructed a new bcc script that watches various events in the
liftime of a dst cache entry. Note that dst_ifdown will take a hold on
the loopback device until the invalidated dst entry gets freed.
[ __dst_free] on DST: ffff883ccabb7900 IF tap1008300eth0 invoked at 1282115677036183
__dst_free
rcu_nocb_kthread
kthread
ret_from_fork
Acked-by: Eric Dumazet <edumazet@google.com>
Signed-off-by: David S. Miller <davem@davemloft.net>
|
||
|---|---|---|
| arch | ||
| block | ||
| certs | ||
| crypto | ||
| Documentation | ||
| drivers | ||
| firmware | ||
| fs | ||
| include | ||
| init | ||
| ipc | ||
| kernel | ||
| lib | ||
| mm | ||
| net | ||
| samples | ||
| scripts | ||
| security | ||
| sound | ||
| tools | ||
| usr | ||
| virt | ||
| .cocciconfig | ||
| .get_maintainer.ignore | ||
| .gitattributes | ||
| .gitignore | ||
| .mailmap | ||
| COPYING | ||
| CREDITS | ||
| Kbuild | ||
| Kconfig | ||
| MAINTAINERS | ||
| Makefile | ||
| README | ||
Linux kernel ============ This file was moved to Documentation/admin-guide/README.rst Please notice that there are several guides for kernel developers and users. These guides can be rendered in a number of formats, like HTML and PDF. In order to build the documentation, use ``make htmldocs`` or ``make pdfdocs``. There are various text files in the Documentation/ subdirectory, several of them using the Restructured Text markup notation. See Documentation/00-INDEX for a list of what is contained in each file. Please read the Documentation/process/changes.rst file, as it contains the requirements for building and running the kernel, and information about the problems which may result by upgrading your kernel.