Thanks Charles for the reply. I was trying to understand the complications of using CONFIG_PREEMPT. But one final question, shouldn't SMP be portable across platforms be it x86 or ARM ? If so the problems should be gone right ?
On Thursday, September 18, 2014 11:30:43 PM UTC+5:30, Charles Steinkuehler wrote: > > I realize the BBB is a single-core SoC. > > My point is enabling PREEMPT code in the kernel *REQUIRES* all kernel > code to be SMP safe (even when running on a single core!), which is why > this option causes stability issues. > > As for the multi-core TI chips with similar drivers, it is not uncommon > for drivers to (mostly) work in a multi-core system without *REALLY* > being SMP safe. See the history of integrating the PREEMPT patch set to > the mainline kernel for a laundry list of obscure, hard-to-trace kernel > bugs that were uncovered in the process, even though Linux had been > running on multi-core x86 systems for quite some time. > > On 9/18/2014 12:34 PM, neo star wrote: > > Hi Charles the BBB is a single core Soc > > > > On Thu, Sep 18, 2014 at 10:47 PM, Charles Steinkuehler > > <cha...@steinkuehler.net <javascript:>> wrote: > >> On 9/18/2014 11:40 AM, Robert Nelson wrote: > >>> > >>> sudo apt-get update > >>> sudo apt-get install linux-image-3.14.19-ti-r22 > >>> > >>> has: CONFIG_PREEMPT_VOLUNTARY > >>> > >>> In the past, preempt broke a lot of things. So i'm always hesitant to > >>> enable it by default across the board. > >> > >> PREEMPT has a tendency to tickle obscure bugs in non-SMP safe kernel > >> code. Many nasty bugs were uncovered as the PREEMPT code got merged > >> into the kernel. Now the core kernel is very SMP safe, but there are > >> still a lot of drivers (ie: "vendor-supplied code for single-core > SoCs") > >> that are not SMP clean. > >> > >> As multi-core ARM systems become more common, the situation should > >> improve (as it did with the x86 over time). > >> > >> -- > >> Charles Steinkuehler > >> cha...@steinkuehler.net <javascript:> > >> > >> -- > >> For more options, visit http://beagleboard.org/discuss > >> --- > >> You received this message because you are subscribed to a topic in the > Google Groups "BeagleBoard" group. > >> To unsubscribe from this topic, visit > https://groups.google.com/d/topic/beagleboard/4eDQvQOkUkc/unsubscribe. > >> To unsubscribe from this group and all its topics, send an email to > beagleboard...@googlegroups.com <javascript:>. > >> For more options, visit https://groups.google.com/d/optout. > > > > > -- > Charles Steinkuehler > cha...@steinkuehler.net <javascript:> > -- For more options, visit http://beagleboard.org/discuss --- You received this message because you are subscribed to the Google Groups "BeagleBoard" group. To unsubscribe from this group and stop receiving emails from it, send an email to beagleboard+unsubscr...@googlegroups.com. For more options, visit https://groups.google.com/d/optout.
