Re: [BUG][PPC64] BUG in 2.6.26.5-rt9 causing Hang
From: Gregory Haskins <hidden>
Date: 2008-09-29 18:15:43
Also in:
lkml
Hi Chirag Chirag Jog wrote:
Hi Gregory, We see the following BUG followed by a hang on the latest kernel 2.6.26.5-rt9 on a Power6 blade (PPC64) It is easily recreated by running the async_handler or sbrk_mutex (realtime tests from ltp) tests.
FYI I am looking at this now. I suspect a dequeue_pushable_task() probably found its way inside a conditional for GROUP_SCHED and inadventently gets compiled away if you disable the feature. Investigating now.. -Greg
quoted hunk ↗ jump to hunk
login: cpu 0x2: Vector: 700 (Program Check) at [c0000000e8e875d0] pc: c00000000005110c: .pick_next_pushable_task+0x54/0x9c lr: c000000000059f50: .push_rt_task+0x44/0x2b4 sp: c0000000e8e87850 msr: 8000000000021032 current = 0xc0000000ea5bb2e0 paca = 0xc000000000608700 pid = 2811, comm = async_handler kernel BUG at kernel/sched_rt.c:1041! <--------------------- enter ? for help [link register ] c000000000059f50 .push_rt_task+0x44/0x2b4 [c0000000e8e87850] c0000000e8e878f0 (unreliable) [c0000000e8e87900] c00000000005a1dc .push_rt_tasks+0x1c/0x38 [c0000000e8e87980] c00000000005a21c .post_schedule_rt+0x24/0x44 [c0000000e8e87a10] c000000000057cbc .finish_task_switch+0xd0/0x180 [c0000000e8e87ab0] c0000000003b6e88 .__schedule+0x6e0/0x798 [c0000000e8e87b90] c0000000003b7148 .schedule+0xec/0x11c [c0000000e8e87c10] c0000000003b7a40 .do_nanosleep+0x6c/0xcc [c0000000e8e87c90] c000000000080738 .hrtimer_nanosleep+0x7c/0x100 [c0000000e8e87d90] c000000000080830 .sys_nanosleep+0x74/0x94 [c0000000e8e87e30] c0000000000086ac syscall_exit+0x0/0x40--- Exception: c00 (System Call) at 0000008026449844SP (400014185f0) is in userspace This is generated by the BUG_ON lines in the pick_next_pushable function introduced by the sched-only-push-once-per-queue.patch . The -rt kernel prior to this patch didnot give such BUGes. All this was tried with CONFIG_GROUP_SCHED=N CONFIG_RT_GROUP_SCHED=N Setting the options CONFIG_GROUP_SCHED=y CONFIG_RT_GROUP_SCHED=Y, seems to solve the problem.
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