Hello,
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()
[1] http://books.gigatux.nl/mirror/kerneldevelopment/0672327201/ch07lev1sec6.html
[2] https://lore.kernel.org/all/5125e39b-0faf-63fc-0c51-982b2a567e21@xxxxxxxxxx/
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.
Cheers
Eric
