mainlining shenanigans
0a66d6f90c
Running a lockedp-enabled kernel on a vim3l board (Amlogic SM1)
leads to the following splat:
[ 13.557138] WARNING: HARDIRQ-safe -> HARDIRQ-unsafe lock order detected
[ 13.587485] ip/456 [HC0[0]:SC0[0]:HE0:SE1] is trying to acquire:
[ 13.625922] ffff000059908cf0 (&irq_desc_lock_class){-.-.}-{2:2}, at: __setup_irq+0xf8/0x8d8
[ 13.632273] which would create a new lock dependency:
[ 13.637272] (&irq_desc_lock_class){-.-.}-{2:2} -> (&ctl->lock){+.+.}-{2:2}
[ 13.644209]
[ 13.644209] but this new dependency connects a HARDIRQ-irq-safe lock:
[ 13.654122] (&irq_desc_lock_class){-.-.}-{2:2}
[ 13.654125]
[ 13.654125] ... which became HARDIRQ-irq-safe at:
[ 13.664759] lock_acquire+0xec/0x368
[ 13.666926] _raw_spin_lock+0x60/0x88
[ 13.669979] handle_fasteoi_irq+0x30/0x178
[ 13.674082] generic_handle_irq+0x38/0x50
[ 13.678098] __handle_domain_irq+0x6c/0xc8
[ 13.682209] gic_handle_irq+0x5c/0xb0
[ 13.685872] el1_irq+0xd0/0x180
[ 13.689010] arch_cpu_idle+0x40/0x220
[ 13.692732] default_idle_call+0x54/0x60
[ 13.696677] do_idle+0x23c/0x2e8
[ 13.699903] cpu_startup_entry+0x30/0x50
[ 13.703852] rest_init+0x1e0/0x2b4
[ 13.707301] arch_call_rest_init+0x18/0x24
[ 13.711449] start_kernel+0x4ec/0x51c
[ 13.715167]
[ 13.715167] to a HARDIRQ-irq-unsafe lock:
[ 13.722426] (&ctl->lock){+.+.}-{2:2}
[ 13.722430]
[ 13.722430] ... which became HARDIRQ-irq-unsafe at:
[ 13.732319] ...
[ 13.732324] lock_acquire+0xec/0x368
[ 13.735985] _raw_spin_lock+0x60/0x88
[ 13.739452] meson_gpio_irq_domain_alloc+0xcc/0x290
[ 13.744392] irq_domain_alloc_irqs_hierarchy+0x24/0x60
[ 13.749586] __irq_domain_alloc_irqs+0x160/0x2f0
[ 13.754254] irq_create_fwspec_mapping+0x118/0x320
[ 13.759073] irq_create_of_mapping+0x78/0xa0
[ 13.763360] of_irq_get+0x6c/0x80
[ 13.766701] of_mdiobus_register_phy+0x10c/0x238 [of_mdio]
[ 13.772227] of_mdiobus_register+0x158/0x380 [of_mdio]
[ 13.777388] mdio_mux_init+0x180/0x2e8 [mdio_mux]
[ 13.782128] g12a_mdio_mux_probe+0x290/0x398 [mdio_mux_meson_g12a]
[ 13.788349] platform_drv_probe+0x5c/0xb0
[ 13.792379] really_probe+0xe4/0x448
[ 13.795979] driver_probe_device+0xe8/0x140
[ 13.800189] __device_attach_driver+0x94/0x120
[ 13.804639] bus_for_each_drv+0x84/0xd8
[ 13.808474] __device_attach+0xe4/0x168
[ 13.812361] device_initial_probe+0x1c/0x28
[ 13.816592] bus_probe_device+0xa4/0xb0
[ 13.820430] deferred_probe_work_func+0xa8/0x100
[ 13.825064] process_one_work+0x264/0x688
[ 13.829088] worker_thread+0x4c/0x458
[ 13.832768] kthread+0x154/0x158
[ 13.836018] ret_from_fork+0x10/0x18
[ 13.839612]
[ 13.839612] other info that might help us debug this:
[ 13.839612]
[ 13.850354] Possible interrupt unsafe locking scenario:
[ 13.850354]
[ 13.855720] CPU0 CPU1
[ 13.858774] ---- ----
[ 13.863242] lock(&ctl->lock);
[ 13.866330] local_irq_disable();
[ 13.872233] lock(&irq_desc_lock_class);
[ 13.878705] lock(&ctl->lock);
[ 13.884297] <Interrupt>
[ 13.886857] lock(&irq_desc_lock_class);
[ 13.891014]
[ 13.891014] *** DEADLOCK ***
The issue can occur when CPU1 is doing something like irq_set_type()
and CPU0 performing an interrupt allocation, for example. Taking
an interrupt (like the one being reconfigured) would lead to a deadlock.
A solution to this is:
- Reorder the locking so that meson_gpio_irq_update_bits takes the lock
itself at all times, instead of relying on the caller to lock or not,
hence making the RMW sequence atomic,
- Rework the critical section in meson_gpio_irq_request_channel to only
cover the allocation itself, and let the gpio_irq_sel_pin callback
deal with its own locking if required,
- Take the private spin-lock with interrupts disabled at all times
Reviewed-by: Jerome Brunet <jbrunet@baylibre.com>
Signed-off-by: Marc Zyngier <maz@kernel.org>
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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.