Messages in this thread | | | Date | Fri, 22 Sep 2023 09:49:59 +0200 | Subject | Re: [PATCH] dmaengine: altera-msgdma: fix descriptors freeing logic | From | Eric Schwarz <> |
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Hello Olivier,
>> Am 20.09.2023 um 21:58 schrieb Olivier Dautricourt: >>> Sparse complains because we first take the lock in msgdma_tasklet -> move >>> locking to msgdma_chan_desc_cleanup. >>> In consequence, move calling of msgdma_chan_desc_cleanup outside of the >>> critical section of function msgdma_tasklet. >>> >>> Use spin_unlock_irqsave/restore instead of just spinlock/unlock to keep >>> state of irqs while executing the callbacks. >> >> What about the locking in the IRQ handler msgdma_irq_handler() itself? - >> Shouldn't spin_unlock_irqsave/restore() be used there as well instead of >> just spinlock/unlock()? > > IMO no: > It is covered by [1]("Locking Between Hard IRQ and Softirqs/Tasklets") > The irq handler cannot be preempted by the tasklet, so the > spin_lock/unlock version is ok. However the tasklet could be interrupted > by the Hard IRQ hence the disabling of irqs with save/restore when > entering critical section. > > It should not be needed to keep interrupts locally disabled while invoking > callbacks, will add this to the commit description. > > [1] https://www.kernel.org/doc/Documentation/kernel-hacking/locking.rst
Thanks for the link. I have read differently here [2] w/ special emphasis on "Lesson 3: spinlocks revisited.".
[2] https://www.kernel.org/doc/Documentation/locking/spinlocks.txt
Cheers Eric
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