On Tue, 26 April 2011 "Paul E. McKenney" <paulmck@xxxxxxxxxxxxxxxxxx> wrote: > On Tue, Apr 26, 2011 at 08:19:04AM +0200, Bruno PrÃmont wrote: > > Though I will use the few minutes I have this evening to try to fetch > > kernel traces of running tasks with sysrq+t which may eventually give > > us a hint at where rcu_thread is stuck/waiting. > > This would be very helpful to me! Here it comes: rcu_kthread (when build processes are STOPped): [ 836.050003] rcu_kthread R running 7324 6 2 0x00000000 [ 836.050003] dd473f28 00000046 5a000240 dd65207c dd407360 dd651d40 0000035c dd473ed8 [ 836.050003] c10bf8a2 c14d63d8 dd65207c dd473f28 dd445040 dd445040 dd473eec c10be848 [ 836.050003] dd651d40 dd407360 ddfdca00 dd473f14 c10bfde2 00000000 00000001 000007b6 [ 836.050003] Call Trace: [ 836.050003] [<c10bf8a2>] ? check_object+0x92/0x210 [ 836.050003] [<c10be848>] ? init_object+0x38/0x70 [ 836.050003] [<c10bfde2>] ? free_debug_processing+0x112/0x1f0 [ 836.050003] [<c103d9fd>] ? lock_timer_base+0x2d/0x70 [ 836.050003] [<c13c8ec7>] schedule_timeout+0x137/0x280 [ 836.050003] [<c10c02b8>] ? kmem_cache_free+0xe8/0x140 [ 836.050003] [<c103db60>] ? sys_gettid+0x20/0x20 [ 836.050003] [<c13c9064>] schedule_timeout_interruptible+0x14/0x20 [ 836.050003] [<c10736e0>] rcu_kthread+0xa0/0xc0 [ 836.050003] [<c104de00>] ? wake_up_bit+0x70/0x70 [ 836.050003] [<c1073640>] ? rcu_process_callbacks+0x60/0x60 [ 836.050003] [<c104d874>] kthread+0x74/0x80 [ 836.050003] [<c104d800>] ? flush_kthread_worker+0x90/0x90 [ 836.050003] [<c13caeb6>] kernel_thread_helper+0x6/0xd a few minutes later when build processes have been killed: [ 966.930008] rcu_kthread R running 7324 6 2 0x00000000 [ 966.930008] dd473f28 00000046 5a000240 dd65207c dd407360 dd651d40 0000035c dd473ed8 [ 966.930008] c10bf8a2 c14d63d8 dd65207c dd473f28 dd445040 dd445040 dd473eec c10be848 [ 966.930008] dd651d40 dd407360 ddfdca00 dd473f14 c10bfde2 00000000 00000001 000007b6 [ 966.930008] Call Trace: [ 966.930008] [<c10bf8a2>] ? check_object+0x92/0x210 [ 966.930008] [<c10be848>] ? init_object+0x38/0x70 [ 966.930008] [<c10bfde2>] ? free_debug_processing+0x112/0x1f0 [ 966.930008] [<c103d9fd>] ? lock_timer_base+0x2d/0x70 [ 966.930008] [<c13c8ec7>] schedule_timeout+0x137/0x280 [ 966.930008] [<c10c02b8>] ? kmem_cache_free+0xe8/0x140 [ 966.930008] [<c103db60>] ? sys_gettid+0x20/0x20 [ 966.930008] [<c13c9064>] schedule_timeout_interruptible+0x14/0x20 [ 966.930008] [<c10736e0>] rcu_kthread+0xa0/0xc0 [ 966.930008] [<c104de00>] ? wake_up_bit+0x70/0x70 [ 966.930008] [<c1073640>] ? rcu_process_callbacks+0x60/0x60 [ 966.930008] [<c104d874>] kthread+0x74/0x80 [ 966.930008] [<c104d800>] ? flush_kthread_worker+0x90/0x90 [ 966.930008] [<c13caeb6>] kernel_thread_helper+0x6/0xd Attached (gzipped) the complete dmesg log (dmesg-t1 contains dmesg from boot until after first sysrq+t -- dmesg-t2 the output of sysrq+t 2 minutes later after having killed build processes). Just in case, I joined slabinfo. Ten minutes later rcu_kthread trace has not changed at all. > > For my part, I will use some plane time today to stare at my code some > more and see what bugs I can find. Possibly useful detail, it's somewhere during my compile that rcu_kthread seems to stop doing its job as after booting things look fine (no slabs piling up). Some part of the whole emerge -> configure and/or emerge -> make -> gcc process tree must be confusing kernel as it's only then that things start piling up (don't know if other kinds of work trigger it as well) Bruno
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