On Fri, 21 Nov 2008, Russell King - ARM Linux wrote: > On Thu, Nov 20, 2008 at 02:11:49PM -0800, Jim Radford wrote: > > Ingo and Steven, > > > > Here's an updated version of the arch/arm changes for dynamic ftrace > > based on top of your latest tip/master. > > Excuse me if I'm rather confused, but... > > When ftrace for ARM was originally merged, neither linux-arm-kernel > nor myself were copied with the patches. Now, I'm being sent updates > to code that I've no understanding of and haven't seen before. > > I mean, yes, it's nice to be copied with patches which are relevent. > It would've been even nicer to have been copied with the patches adding > ftrace in the first place, so people knew something about it and were > aware of the changes. > > It seems to me like there's been a total breakdown of communication > when ftrace was initially merged...
Yes I totally agree that in the beginning there was a breakdown of communication. I myself just learned of the ARM port. > > So, questions: has ftrace actually been tested on ARM at all? Has it > been reviewed? Which ARM platforms has it been tried on? How stable > is it? How has it been implemented on ARM? Does it rely on any CPU > specific behaviour? > > Looking at the git history, ftrace was merged via Ingo, so I assume > that Ingo has some understanding of this code. So, for the time being > if these are urgent updates, I suggest that updates go through Ingo's > tree rather than mine. I would suggest that they at least get an ACK from you. The original code should have too. > > And looking at arch/arm/kernel/ftrace.c, it's incompatible with Thumb2 > which we've been working towards supporting. What about SMP? ARM is > a SMP capable architecture now, and I see no locking in there - what > I do see is static data with pointers to it being returned to other > code... Yuck. Some of this code will be redesigned in 29. But as for the locking, this code is run under kstop_machine. Which means that even on SMP architectures, this acts like a UP box. Some of the code can be run outside of kstop_machine, but it is protected by locks in the module code. I'll take a look at the ftrace.c arm code and see if there's any problems with it. I wrote the x86 version as well as the coming PowerPC port. Thanks, -- Steve _______________________________________________ Linuxppc-dev mailing list Linuxppc-dev@ozlabs.org https://ozlabs.org/mailman/listinfo/linuxppc-dev
