On 02/19/2016 09:10 AM, Anand Moon wrote: > Hi Krzysztof, > > On 19 February 2016 at 12:50, Krzysztof Kozlowski > <k.kozlowski@xxxxxxxxxxx> wrote: >> On 19.02.2016 15:39, Anand Moon wrote: >>> Hi Krzysztof, >>> >>> On 19 February 2016 at 11:36, Krzysztof Kozlowski >>> <k.kozlowski@xxxxxxxxxxx> wrote: >>>> 2016-02-19 2:21 GMT+09:00 Anand Moon <linux.amoon@xxxxxxxxx>: >>>>> From: Anand Moon <linux.amoon@xxxxxxxxx> >>>>> >>>>> pl330_tasklet tasklet uses the same spinlock pch->lock for safe IRQ locking. >>>>> It's safe to initialize pl330_tasklet tasklet after release of the locking. >>>> >>>> This is tasklet init, not tasklet execution (which you are referring >>>> to in first sentence). I don't get how usage of spinlock during >>>> execution guarantees the safeness during init... Please describe why >>>> this is safe. >>>> >>>> Best regards, >>>> Krzysztof >>>> >>> >>> http://lxr.free-electrons.com/source/drivers/dma/pl330.c#L1972 >>> >>> pl330_tasklet function which is initiated by tasklet_init is trying to lock >>> using same spin_unlock_irqsave/restore pch->lock. >> >> tasklet_init does not call pl330_tasklet (if this is what you mean by >> "initiated"). What is the correlation? Why are you referring to the >> locks in pl330_tasklet? >> >>> So better release the pch->lock and then initialize the tasklet_init. >> >> Why "better"? >> >> Best regards, >> Krzysztof >> > > On SMP arch, tasklet_init could spawn the pl330_tasklet routine, > it could be any CPU which could take up this task. > So just for good timing of Initialization of the pl330_tasklet after > spin_unlock_irqrestore. > That is what I can figure out. Hi, tasklet_init() does not spwan the tasklet function, tasklet_schedule() does that. But there is still room for optimization here. If you want to move the tasklet_init() call please move it into pl330_probe() next to where the channel is allocated. There is no need to re-initialize the tasklet each time the channel is requested. - Lars -- To unsubscribe from this list: send the line "unsubscribe dmaengine" in the body of a message to majordomo@xxxxxxxxxxxxxxx More majordomo info at http://vger.kernel.org/majordomo-info.html
