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author | Bjorn Andersson <bjorn.andersson@linaro.org> | 2021-06-11 10:00:03 -0700 |
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committer | Rob Clark <robdclark@chromium.org> | 2021-06-23 07:33:55 -0700 |
commit | c96348a8fbff90ef610b0323218e9d585683bdd2 (patch) | |
tree | d4d604dc8d3a0d9c1af7b19a3a894448b30af250 /drivers/gpu/drm/msm/disp/dpu1/dpu_kms.h | |
parent | e25e92e08e32c6bf63a968929d232f13dcf9938c (diff) | |
download | linux-c96348a8fbff90ef610b0323218e9d585683bdd2.tar.bz2 |
drm/msm/dpu: Avoid ABBA deadlock between IRQ modules
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>
Diffstat (limited to 'drivers/gpu/drm/msm/disp/dpu1/dpu_kms.h')
-rw-r--r-- | drivers/gpu/drm/msm/disp/dpu1/dpu_kms.h | 2 |
1 files changed, 0 insertions, 2 deletions
diff --git a/drivers/gpu/drm/msm/disp/dpu1/dpu_kms.h b/drivers/gpu/drm/msm/disp/dpu1/dpu_kms.h index 2b23696ee7fd..323a6bce9e64 100644 --- a/drivers/gpu/drm/msm/disp/dpu1/dpu_kms.h +++ b/drivers/gpu/drm/msm/disp/dpu1/dpu_kms.h @@ -82,14 +82,12 @@ struct dpu_irq_callback { * struct dpu_irq: IRQ structure contains callback registration info * @total_irq: total number of irq_idx obtained from HW interrupts mapping * @irq_cb_tbl: array of IRQ callbacks setting - * @cb_lock: callback lock * @debugfs_file: debugfs file for irq statistics */ struct dpu_irq { u32 total_irqs; struct list_head *irq_cb_tbl; atomic_t *irq_counts; - spinlock_t cb_lock; }; struct dpu_kms { |