On 04.03.2014 23:55, David Miller wrote: > From: Kirill Tkhai <tkhai@xxxxxxxxx> > Date: Wed, 12 Feb 2014 12:33:58 +0400 > >> 12.02.2014, 11:48, "Allen Pais" <allen.pais@xxxxxxxxxx>: >> >>> On Wednesday 12 February 2014 02:43 AM, Kirill Tkhai wrote: >>>> 06.01.2014, 07:56, "Allen Pais" <allen.pais@xxxxxxxxxx>: >>>>> In the attempt of get PREEMPT_RT working on sparc64 using >>>>> linux-stable-rt version 3.10.22-rt19+, the kernel crash >>>>> with the following trace: >>>>> >>>>> [ 1487.027884] I7: <rt_mutex_setprio+0x3c/0x2c0> >>>>> [ 1487.027885] Call Trace: >>>>> [ 1487.027887] [00000000004967dc] rt_mutex_setprio+0x3c/0x2c0 >>>>> [ 1487.027892] [00000000004afe20] task_blocks_on_rt_mutex+0x180/0x200 >>>>> [ 1487.027895] [0000000000819114] rt_spin_lock_slowlock+0x94/0x300 >>>>> [ 1487.027897] [0000000000817ebc] __schedule+0x39c/0x53c >>>>> [ 1487.027899] [00000000008185fc] schedule+0x1c/0xc0 >>>>> [ 1487.027908] [000000000048fff4] smpboot_thread_fn+0x154/0x2e0 >>>>> [ 1487.027913] [000000000048753c] kthread+0x7c/0xa0 >>>>> [ 1487.027920] [00000000004060c4] ret_from_syscall+0x1c/0x2c >>>>> [ 1487.027922] [0000000000000000] (null) >>> Now, consistently I've been getting sun4v_data_access_exception. >>> Here's the trace: >>> [ 4673.360121] sun4v_data_access_exception: ADDR[0000080000000000] CTX[0000] TYPE[0004], going. >> >> I've never dived at sparc's tlb before, but it seems now I'm understanding. >> >> arch_enter_lazy_mmu_mode() makes possible delayed tlb flushing. In !RT kernel >> you collect flush requests before you really flush all of them. >> >> In RT you collect them too, but you are able to be preempted in any moment. >> So, you may switch to other process with unflushed tlb, which is very bad. >> >> Try to not to set tb->active = 1; in arch_enter_lazy_mmu_mode(). Set it to zero. >> We will look if this robust fix helps. > > Sorry for coming into this discussion so late. > > Indeed, the pending flushes are per-cpu and we must flush them out in the > event of a preemption. > > PowerPC does the same exact thing with arch_enter_lazy_mmu_mode(), in > fact that's where I copied the logic from. Does PowerPC not work with > -rt? :-) > It does not work, but we will :) -- To unsubscribe from this list: send the line "unsubscribe sparclinux" in the body of a message to majordomo@xxxxxxxxxxxxxxx More majordomo info at http://vger.kernel.org/majordomo-info.html
