On Wednesday 02 October 2013 01:22 PM, Stephen Boyd wrote: > On 10/02/13 10:14, Santosh Shilimkar wrote: >> On Wednesday 02 October 2013 01:09 PM, Will Deacon wrote: >>> On Wed, Oct 02, 2013 at 05:55:28PM +0100, Santosh Shilimkar wrote: >>>> The sched_clock code uses 2 levels of function pointers, sched_clock_func() >>>> and read_sched_clock() but the no sched_clock check in postinit() just >>>> checks read_sched_clock(). >>>> >>>> This leads to kernel falling back to jiffy based sched clock even in >>>> presence of sched_clock_func() which is not desirable. >>>> >>>> Fix the postinit() check to avoid the issue. Probably the issue is hidden >>>> so far on most of the arm SOCs because of already existing sched_clock >>>> registrations apart from arch_timer sched_clock. One can reproduce the >>>> issue by just have arch_timer as sched_clock >>> Isn't this just an issue with the arch timer driver not calling >>> setup_sched_clock? Instead, we munge around with sched_clock_func directly, >>> which doesn't appear to be the way anybody else deals with this. >>> >> I thought about that option as well but was not sure since even in that case >> the check is not complete. We just ensure that function is popullated. > > Yes, nothing is actually broken because sched_clock_func() won't try to > use the jiffy based read_sched_clock() function. I'm not sure we > actually need this patch besides to remove a useless timer that updates > the jiffy epoch. Can we wait until my 64-bit sched_clock patch series > lands in 3.13? It looks like I still need an ack from Will or Catalin on > the architected timer patch before the clocksource folks pick it up. > Really... I have not created patch out of fun. Its broken on my keystone machine at least where the sched_clock is falling back on jiffy based sched_clock even in presence of arch_timer sched_clock.
Regards, Santosh -- To unsubscribe from this list: send the line "unsubscribe linux-kernel" in the body of a message to majord...@vger.kernel.org More majordomo info at http://vger.kernel.org/majordomo-info.html Please read the FAQ at http://www.tux.org/lkml/
