Messages in this thread | | | Date | Wed, 21 Apr 2010 10:31:45 -0700 | From | "Paul E. McKenney" <> | Subject | Re: [patch 0/5] rcu head debugobjects |
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On Sat, Apr 17, 2010 at 05:48:49PM -0700, Paul E. McKenney wrote: > On Sat, Apr 17, 2010 at 08:48:37AM -0400, Mathieu Desnoyers wrote: > > Here is a repost of the rcu head debugobjects patchset, with updated changelogs. > > > > Paul, this would be ready to be integrated with the RCU patches. > > Thank you, Mathieu, queued up for 2.6.35!
And testing got me the following debugobjects splat, which baffles me. My first thought was that one of the synchronize_rcu() variants was missing the init_rcu_head_on_stack(), but not so. Then I started looking through the debugobjects code, and found the following:
static void debug_object_is_on_stack(void *addr, int onstack) { int is_on_stack; static int limit;
if (limit > 4) return;
This really confuses me. We are using a static variable, but as near as I can tell, it is being guarded by a per-bucket lock:
raw_spin_lock_irqsave(&db->lock, flags);
If I understand correctly, this means that multiple CPUs might be concurrently updating the static variable "limit", which might in turn be causing the splat below.
Or am I missing something?
Thanx, Paul
------------------------------------------------------------------------
ODEBUG: object is on stack, but not annotated ------------[ cut here ]------------ Badness at lib/debugobjects.c:294 NIP: c0000000002c76f0 LR: c0000000002c76ec CTR: c00000000041ecd8 REGS: c0000001de71b280 TRAP: 0700 Tainted: G W (2.6.34-rc3-autokern1) MSR: 8000000000029032 <EE,ME,CE,IR,DR> CR: 24000424 XER: 0000000f TASK = c0000001de7dca00[3695] 'arping' THREAD: c0000001de718000 CPU: 1 GPR00: c0000000002c76ec c0000001de71b500 c00000000096c048 0000000000000034 GPR04: 0000000000000001 c000000000063918 0000000000000000 0000000000000002 GPR08: 0000000000000003 0000000000000000 c000000000086f68 c0000001de7dca00 GPR12: 000000000000256d c0000000074e4200 0000000000000000 0000000000000000 GPR16: 0000000000000000 0000000000000000 0000000000000000 00000000201b8f60 GPR20: 00000000201b8f70 00000000201b8f48 0000000000000000 c0000000008766b8 GPR24: c0000001de71b800 0000000000000001 c0000000008ad400 c000000001247478 GPR28: c0000000e6abb8c0 c0000000e6abb8c0 c000000000904570 c000000001247470 NIP [c0000000002c76f0] .__debug_object_init+0x314/0x40c LR [c0000000002c76ec] .__debug_object_init+0x310/0x40c Call Trace: [c0000001de71b500] [c0000000002c76ec] .__debug_object_init+0x310/0x40c (unreliable) [c0000001de71b5d0] [c00000000007d990] .rcuhead_fixup_activate+0x40/0xdc [c0000001de71b660] [c0000000002c6a7c] .debug_object_fixup+0x4c/0x74 [c0000001de71b6f0] [c0000000000c5e54] .__call_rcu+0x3c/0x1d4 [c0000001de71b790] [c0000000000c6050] .synchronize_rcu+0x4c/0x6c [c0000001de71b870] [c0000000004be218] .synchronize_net+0x10/0x24 [c0000001de71b8e0] [c0000000005498c8] .packet_release+0x1d4/0x274 [c0000001de71b990] [c0000000004ac1f0] .sock_release+0x54/0x124 [c0000001de71ba20] [c0000000004ac9e4] .sock_close+0x34/0x4c [c0000001de71baa0] [c00000000012469c] .__fput+0x174/0x264 [c0000001de71bb40] [c000000000120c54] .filp_close+0xb0/0xd8 [c0000001de71bbd0] [c000000000065e70] .put_files_struct+0x1a8/0x314 [c0000001de71bc70] [c000000000067e04] .do_exit+0x234/0x6f0 [c0000001de71bd30] [c000000000068354] .do_group_exit+0x94/0xc8 [c0000001de71bdc0] [c00000000006839c] .SyS_exit_group+0x14/0x28 [c0000001de71be30] [c000000000008554] syscall_exit+0x0/0x40 Instruction dump: 7f80b000 419e0030 2fa00000 e93e8140 380b0001 90090000 419e000c e87e8148 48000008 e87e8150 4bd9cb89 60000000 <0fe00000> 801c0010 2f800003 419e0024
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