c96348a8fb
Handling of the interrupt callback lists is done in dpu_core_irq.c,
under the "cb_lock" spinlock. When these operations results in the need
for enableing or disabling the IRQ in the hardware the code jumps to
dpu_hw_interrupts.c, which protects its operations with "irq_lock"
spinlock.
When an interrupt fires, dpu_hw_intr_dispatch_irq() inspects the
hardware state while holding the "irq_lock" spinlock and jumps to
dpu_core_irq_callback_handler() to invoke the registered handlers, which
traverses the callback list under the "cb_lock" spinlock.
As such, in the event that these happens concurrently we'll end up with
a deadlock.
Prior to '1c1e7763a6d4 ("drm/msm/dpu: simplify IRQ enabling/disabling")'
the enable/disable of the hardware interrupt was done outside the
"cb_lock" region, optimitically by using an atomic enable-counter for
each interrupt and an warning print if someone changed the list between
the atomic_read and the time the operation concluded.
Rather than re-introducing the large array of atomics, this change
embraces the fact that dpu_core_irq and dpu_hw_interrupts are deeply
entangled and make them share the single "irq_lock".
Following this step it's suggested that we squash the two parts into a
single irq handling thing.
Fixes: 1c1e7763a6d4 ("drm/msm/dpu: simplify IRQ enabling/disabling")
Signed-off-by: Bjorn Andersson <bjorn.andersson@linaro.org>
Reviewed-by: Dmitry Baryshkov <dmitry.baryshkov@linaro.org>
Link: https://lore.kernel.org/r/20210611170003.3539059-1-bjorn.andersson@linaro.org
Signed-off-by: Rob Clark <robdclark@chromium.org>
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.