On Tue, Dec 10, 2019 at 04:36:34PM +0100, Andreas Färber wrote:
Hi S*deeps,
Am 10.12.19 um 16:08 schrieb Sudeep Holla via TF-A:
[...]
(I see the roles being exchanged, OS was slave + producer and not sure what you are referring has master above. Anyways use KDUMP and features like that if you need RAM dump for portions of memory given to the kernel.
Sorry to barge in, but it sounds like you're not quite understanding each other in this ever-growing thread: Sandeep said his use case was a SmartNIC, so I assume the logging direction is from SoC on the SmartNIC to host SoC via PCIe? Think dmesg-like logs, from one host for another - I fail to see how Sudeep's kdump suggestion could help here.
Sorry for my lack of knowledge there. And for sure, you have explained it much better now. Since I was assuming some kind of use-case(like crash logs) and something similar I suggested kdump above. I agree it was irrelevant to the discussion.
But maybe I'm not understanding properly, in which case I'll just blame your abstract master/slave discussions. :)
:)
To me and my ignorance however it sounds like this use case has nothing really to do with shutdown?
Agreed, and I thought I asked this as what happens when the logging process terminates ? It should be handled in similar manner. Sorry if I have missed to ask this aloud, it might have died in my thoughts and didn't come out.
If the log producer does not flush their logs after say each line ending, then also without shutdown you have no guarantee of the logs reaching the consumer in a timely manner through all the producer's caches, no?
Absolutely, I completely agree.
Think of watchdogs, power loss or other irregular resets that PSCI can do nothing about. Especially for logs, those error conditions would be the most important to receive data of.
Indeed. That's the reason I was trying to concentrate this as producer and consumer problem and graceful shutdown/restart can provide opportunity for them to handle it correctly through some sort of notifications. The assumption of coherent memory and the DRAM retaining content after the producer has terminated bother me.
-- Regards, Sudeep