Philippe Gerum wrote: > On Fri, 2009-10-02 at 21:25 +0200, Jan Kiszka wrote: >> Gilles Chanteperdrix wrote: >>> Philippe Gerum wrote: >>>> On Tue, 2009-09-29 at 19:31 +0200, Gilles Chanteperdrix wrote: >>>>> Hi guys, >>>>> >>>>> full of energy after this tremendous first XUM, >>>> Agreed, thanks to the DENX folks for having thought of it in the first >>>> place, and organized it nicely. >>>> >>>>> I would like to start a >>>>> discussion about what people would like to see in the 2.5 branch. >>>>> >>>> Jan has described the situation quite accurately already, regarding the >>>> trade-off between getting everything we want into 2.5 so that no 2.6 is >>>> required, and releasing the too long-awaited 2.5 asap. >>>> >>>> As you mentioned already, the key issue is ABI stability. >>>> Any change we want before 3.0 that breaks the ABI should preferably go >>>> to 2.5, so that we don't end up maintaining 2.5.x, 2.6.x and 3.x. At any >>>> rate, we could not afford the latter anyway. This is a different matter >>>> than API issues; we already allowed API extensions during a stable >>>> cycle, provided they do not break existing application code (except in >>>> emergency cases), so I see no problem in pushing a few more services to >>>> 2.5.1 and beyond, provided that condition is met. >>>> >>>>> Here is a first list, please feel free to criticize it: >>>>> - signals in primary domain (something that we almost forgot) >>>> Yes, this one must be in. At least, we should break the ABI one more >>>> time for this before releasing 2.5.0. This item has priority #1 for >>>> me, since providing that infrastructure will enable a series of >>>> additional services to be implemented properly. In fact, this is more a >>>> matter of allowing nucleus callouts to user-space than anything else; >>>> POSIX RT signals in full primary mode being an application of them. >>> Ok. So, if we add the core skin fdtable, this leaves us with two items: >>> - signals in primary domain >> Sorry, I neither see the need nor feel comfortable about the impact / >> side effects of such an extension. >> > > This extension is mandatory to allow callouts from the nucleus to a > user-space application without forcing the latter to leave primary mode. > This is direly needed when implementing some legacy RTOS services, and > currently only available from kernel to kernel. We need this 1) to > implement POSIX RT signals (a long term maintenance release like 2.5 > must have those), 2) implement missing services from existing skins > (VxWorks comes to mind), 3) provide an upgrade path from 2.5.x to 3.x, > for people who will have to move their apps to userland in v3, and as > such should be able to anticipate that move with 2.5. > > The impact is minimal, we have discussed the general idea in a previous > thread actually. This is typically something that is implemented between > the shadow support code and the generic syscall code, this does not have > to leak anywhere else.
I understand the need for it now, but I will likely not share your optimism regarding the orthogonality of this change until I saw the code. My worries about when we will see 2.5.0 are increasing again. Jan
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