Re: [PATCH] dmaengine: plx_dma: Fix potential deadlock on &plxdev->ring_lock

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Am 27.07.2023 um 08:48 schrieb Chengfeng Ye:
Hi Logan and Christophe,

Thanks much for the reply and reminder, and yes, spin_lock_bh() should
be better.

When I wrote the patch I thought the spin_lock_bh() cannot be nested,
and afraid that if some outside callers called .dma_tx_status() callback
with softirq already disable, then spin_unlock_bh() would unintentionally
re-enable softirq(). spin_lock_irqsave() is always safer in general thus I
used it.

But I just check the document [1] about these API and found that _bh()
can be nested. Then use spin_lock_bh() should be better due to
performance concern.

So perhaps we should just revert 1d05a0bdb420?
Then for this one I think revert 1d05a0bdb420 should be enough. May I
ask to revert that patch, should I do anything further? (like sending
a new patch).

as explained in another reply [1], would spin_lock_bh() be enough in
such a case?
For the another one [2], I would send a v2 patch to change to spin_lock_bh()


For uniformity reason across drivers and also that not something else gets missed please compare your requirements and solution to the implementation of the "altera-msgdma" driver (altera-msgdma.c).

W/ special emphasis on commit edf10919e5fc ("dmaengine: altera: fix spinlock usage")

spin_lock_bh was changed to spin_lock_irqsave w/ this patch.


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