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After migrating my laptop from 4.19-LTS to 5.4-LTS a while ago I noticed
that my Ethernet port to which a bond and a VLAN interface are attached
appeared to remain up after resuming from suspend with the cable unplugged
(and that problem still persists with 5.10-LTS).
It happens that the following happens:
- the network driver (e1000e here) prepares to suspend, calls e1000e_down()
which calls netif_carrier_off() to signal that the link is going down.
- netif_carrier_off() adds a link_watch event to the list of events for
this device
- the device is completely stopped.
- the machine suspends
- the cable is unplugged and the machine brought to another location
- the machine is resumed
- the queued linkwatch events are processed for the device
- the device doesn't yet have the __LINK_STATE_PRESENT bit and its events
are silently dropped
- the device is resumed with its link down
- the upper VLAN and bond interfaces are never notified that the link had
been turned down and remain up
- the only way to provoke a change is to physically connect the machine
to a port and possibly unplug it.
The state after resume looks like this:
$ ip -br li | egrep 'bond|eth'
bond0 UP e8:6a:64:64:64:64 <BROADCAST,MULTICAST,MASTER,UP,LOWER_UP>
eth0 DOWN e8:6a:64:64:64:64 <NO-CARRIER,BROADCAST,MULTICAST,SLAVE,UP>
eth0.2@eth0 UP e8:6a:64:64:64:64 <BROADCAST,MULTICAST,SLAVE,UP,LOWER_UP>
Placing an explicit call to netdev_state_change() either in the suspend
or the resume code in the NIC driver worked around this but the solution
is not satisfying.
The issue in fact really is in link_watch that loses events while it
ought not to. It happens that the test for the device being present was
added by commit
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| block | ||
| certs | ||
| crypto | ||
| Documentation | ||
| drivers | ||
| fs | ||
| include | ||
| init | ||
| ipc | ||
| kernel | ||
| lib | ||
| LICENSES | ||
| mm | ||
| net | ||
| samples | ||
| scripts | ||
| security | ||
| sound | ||
| tools | ||
| usr | ||
| virt | ||
| .clang-format | ||
| .cocciconfig | ||
| .get_maintainer.ignore | ||
| .gitattributes | ||
| .gitignore | ||
| .mailmap | ||
| COPYING | ||
| CREDITS | ||
| Kbuild | ||
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| MAINTAINERS | ||
| Makefile | ||
| README | ||
Linux kernel
============
There are several guides for kernel developers and users. These guides can
be rendered in a number of formats, like HTML and PDF. Please read
Documentation/admin-guide/README.rst first.
In order to build the documentation, use ``make htmldocs`` or
``make pdfdocs``. The formatted documentation can also be read online at:
https://www.kernel.org/doc/html/latest/
There are various text files in the Documentation/ subdirectory,
several of them using the Restructured Text markup notation.
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.