On Tue, Sep 18, 2012 at 01:42:49PM -0600, Shuah Khan wrote: > Are you ok with the system wide and per device error counts I added? Any > comments on the overall approach? The general approach of having error counters is fine. But the addresses allocated/addresses checked thing should be done per allocation and not with counter comparison for several reasons: 1. When doing it per-allocation we know exactly which allocation was not checked and can tell the driver developer. The code saves stack-traces for that. This is much more useful than telling the developer 'somewhere you do not check your dma-handles' 2. Checking this per-allocation gives you the per-device and also the per-driver checking you want. 3. You don't need to change 'struct device' for that. There are more reasons, like that this approach fits a lot better to the general idea of the DMA-API debugging code. > The approach you suggested will cover the cases where drivers fail to > check good map cases. We won't able to catch failed maps that get used > without checks. Are you not concerned about these cases? These could > cause a silent error with wild writes or could bring the system down. Or > are you recommending changing the infrastructure to track failed maps as > well? It is fine to only check the good-map cases. Think about what DMA-debugging is good for: It is a tool for driver developers to find bugs in their code they wouldn't notice otherwise. An unchecked bad-map case is a bug they would notice otherwise. So if we check only the good-map cases and warn the driver developers about non-checked addresses they fix it and make the drivers more robust against failed allocations, fixing also the bad-map cases. > I am still pursuing a way to track failed map cases. I combined the flag > idea with one of the ideas I am looking into. Details below: (if this > sounds like a reasonable approach, I can do v2 patch and we can discuss > the code) Why do you want to track the bad-map cases? Joerg -- AMD Operating System Research Center Advanced Micro Devices GmbH Einsteinring 24 85609 Dornach General Managers: Alberto Bozzo Registration: Dornach, Landkr. Muenchen; Registerger. Muenchen, HRB Nr. 43632 -- To unsubscribe from this list: send the line "unsubscribe linux-doc" in the body of a message to majordomo@xxxxxxxxxxxxxxx More majordomo info at http://vger.kernel.org/majordomo-info.html
