On 04/24/2012 12:18 PM, Jon Masters wrote: > On 04/23/2012 04:31 PM, Nicolas Pitre wrote: >> On Mon, 23 Apr 2012, Andrew Haley wrote: >> >>> On 04/23/2012 06:36 PM, Thomas Meyer wrote: >>>> I'm running the Ubuntun 2.6.38 Tegra2 kernel (because of their fbdev >>>> support) on top of Fedora 17 armv5el on an Toshiba AC100 Laptop. The >>>> rsyslog package crashed everytime because of the missing kernel support >>>> of cmpxchg64. So when relying on the kernel helpers make sure that the >>>> resp. kernel support exists. >>> >>> Indeed. I had to write a workaround in IcedTea (i.e. java) on ARM for >>> just this reason. If you can't depend on a kernel helper being there I >>> can't see it's of any use. >> >> Kernel helpers don't disappear with time. You therefore can probe for >> their availability (see the documentation) in case the kernel support >> could be backported, or just refuse to run if the kernel version isn't >> recent enough. This is not much different from relying on a new >> syscall. > > I wasn't going to reply yet just due to lack of time and because Nico > covered the kernel helper stuff so well in his earlier posts. But just > to add, these kernel helpers have grown a little over time in higher > kernel revisions, but there is a mechanism to discover the revision > available (note: these are not VDSO but if it helps folks understand > them, think of them like that). They are the right way to solve the > atomics problem as best as we can for older devices. I believe the > correct thing to do is to get broken upstream projects to adopt generic > non-reimplemented-of-their-own routines that will transparently use the > kernel helpers if needed. It would be sad to give up on v5 just yet, but > we are also in this for the longer haul, and newer Plugs are going to be > switching to v7 over time. So, in due course, I am open to also > considering a switch to v6 (with or without smp). "broken" does not mean to imply "wrong". I mean stuff that is failing for silly reasons. This is not a jab at Java either - some projects need their own locking implementations. I wish we had the load/store reservation support on older ARM, but sadly we do not. Jon. _______________________________________________ arm mailing list arm@xxxxxxxxxxxxxxxxxxxxxxx https://admin.fedoraproject.org/mailman/listinfo/arm
