c026d97010
The notifier_call() of the slave interface removes rmnet interface with
unregister_netdevice_queue().
But, before calling unregister_netdevice_queue(), it acquires
rcu readlock.
In the RCU critical section, sleeping isn't be allowed.
But, unregister_netdevice_queue() internally calls synchronize_net(),
which would sleep.
So, suspicious RCU usage warning occurs.
Test commands:
modprobe rmnet
ip link add dummy0 type dummy
ip link add dummy1 type dummy
ip link add rmnet0 link dummy0 type rmnet mux_id 1
ip link set dummy1 master rmnet0
ip link del dummy0
Splat looks like:
[ 79.639245][ T1195] =============================
[ 79.640134][ T1195] WARNING: suspicious RCU usage
[ 79.640852][ T1195] 5.6.0-rc1+ #447 Not tainted
[ 79.641657][ T1195] -----------------------------
[ 79.642472][ T1195] ./include/linux/rcupdate.h:273 Illegal context switch in RCU read-side critical section!
[ 79.644043][ T1195]
[ 79.644043][ T1195] other info that might help us debug this:
[ 79.644043][ T1195]
[ 79.645682][ T1195]
[ 79.645682][ T1195] rcu_scheduler_active = 2, debug_locks = 1
[ 79.646980][ T1195] 2 locks held by ip/1195:
[ 79.647629][ T1195] #0: ffffffffa3cf64f0 (rtnl_mutex){+.+.}, at: rtnetlink_rcv_msg+0x457/0x890
[ 79.649312][ T1195] #1: ffffffffa39256c0 (rcu_read_lock){....}, at: rmnet_config_notify_cb+0xf0/0x590 [rmnet]
[ 79.651717][ T1195]
[ 79.651717][ T1195] stack backtrace:
[ 79.652650][ T1195] CPU: 3 PID: 1195 Comm: ip Not tainted 5.6.0-rc1+ #447
[ 79.653702][ T1195] Hardware name: innotek GmbH VirtualBox/VirtualBox, BIOS VirtualBox 12/01/2006
[ 79.655037][ T1195] Call Trace:
[ 79.655560][ T1195] dump_stack+0x96/0xdb
[ 79.656252][ T1195] ___might_sleep+0x345/0x440
[ 79.656994][ T1195] synchronize_net+0x18/0x30
[ 79.661132][ T1195] netdev_rx_handler_unregister+0x40/0xb0
[ 79.666266][ T1195] rmnet_unregister_real_device+0x42/0xb0 [rmnet]
[ 79.667211][ T1195] rmnet_config_notify_cb+0x1f7/0x590 [rmnet]
[ 79.668121][ T1195] ? rmnet_unregister_bridge.isra.6+0xf0/0xf0 [rmnet]
[ 79.669166][ T1195] ? rmnet_unregister_bridge.isra.6+0xf0/0xf0 [rmnet]
[ 79.670286][ T1195] ? __module_text_address+0x13/0x140
[ 79.671139][ T1195] notifier_call_chain+0x90/0x160
[ 79.671973][ T1195] rollback_registered_many+0x660/0xcf0
[ 79.672893][ T1195] ? netif_set_real_num_tx_queues+0x780/0x780
[ 79.675091][ T1195] ? __lock_acquire+0xdfe/0x3de0
[ 79.675825][ T1195] ? memset+0x1f/0x40
[ 79.676367][ T1195] ? __nla_validate_parse+0x98/0x1ab0
[ 79.677290][ T1195] unregister_netdevice_many.part.133+0x13/0x1b0
[ 79.678163][ T1195] rtnl_delete_link+0xbc/0x100
[ ... ]
Fixes: ceed73a2cf4a ("drivers: net: ethernet: qualcomm: rmnet: Initial implementation")
Signed-off-by: Taehee Yoo <ap420073@gmail.com>
Signed-off-by: David S. Miller <davem@davemloft.net>
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.