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24efc6d36d
The can_rx_unregister() can be called from NAPI (soft IRQ) context, at least by j1939 stack. This leads to potential dead lock with &net->can.rcvlists_lock called from can_rx_register: =============================================================================== WARNING: inconsistent lock state 4.19.0-20181029-1-g3e67f95ba0d3 #3 Not tainted -------------------------------- inconsistent {SOFTIRQ-ON-W} -> {IN-SOFTIRQ-W} usage. testj1939/224 [HC0[0]:SC1[1]:HE1:SE0] takes: 1ad0fda3 (&(&net->can.rcvlists_lock)->rlock){+.?.}, at: can_rx_unregister+0x4c/0x1ac {SOFTIRQ-ON-W} state was registered at: lock_acquire+0xd0/0x1f4 _raw_spin_lock+0x30/0x40 can_rx_register+0x5c/0x14c j1939_netdev_start+0xdc/0x1f8 j1939_sk_bind+0x18c/0x1c8 __sys_bind+0x70/0xb0 sys_bind+0x10/0x14 ret_fast_syscall+0x0/0x28 0xbedc9b64 irq event stamp: 2440 hardirqs last enabled at (2440): [<c01302c0>] __local_bh_enable_ip+0xac/0x184 hardirqs last disabled at (2439): [<c0130274>] __local_bh_enable_ip+0x60/0x184 softirqs last enabled at (2412): [<c08b0bf4>] release_sock+0x84/0xa4 softirqs last disabled at (2415): [<c013055c>] irq_exit+0x100/0x1b0 other info that might help us debug this: Possible unsafe locking scenario: CPU0 ---- lock(&(&net->can.rcvlists_lock)->rlock); <Interrupt> lock(&(&net->can.rcvlists_lock)->rlock); *** DEADLOCK *** 2 locks held by testj1939/224: #0: 168eb13b (rcu_read_lock){....}, at: netif_receive_skb_internal+0x3c/0x350 #1: 168eb13b (rcu_read_lock){....}, at: can_receive+0x88/0x1c0 =============================================================================== To avoid this situation, we should use spin_lock_bh() instead of spin_lock(). Signed-off-by: Oleksij Rempel <o.rempel@pengutronix.de> Acked-by: Oliver Hartkopp <socketcan@hartkopp.net> Signed-off-by: Marc Kleine-Budde <mkl@pengutronix.de>
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.