Paul,

-tip testing found that these patches are causing a crash:

[   24.995999] BUG: unable to handle kernel NULL pointer dereference at (null)
[   24.995999] IP: [<ffffffff810bd645>] perf_swcounter_ctx_event+0x1f4/0x26c
[   24.995999] PGD 3b555067 PUD 3b5a1067 PMD 0 
[   24.995999] Oops: 0000 [#1] SMP DEBUG_PAGEALLOC
[   24.995999] last sysfs file: /sys/devices/system/cpu/cpu1/online
[   24.995999] CPU 0 
[   24.995999] Modules linked in:
[   24.995999] Pid: 3217, comm: S99local Tainted: G        W  2.6.30-rc7-tip-01947-gd584b05-dirty #47106 System Product Name
[   24.995999] RIP: 0010:[<ffffffff810bd645>]  [<ffffffff810bd645>] perf_swcounter_ctx_event+0x1f4/0x26c
[   24.995999] RSP: 0018:ffff88003b595be8  EFLAGS: 00010202
[   24.995999] RAX: 0100000000000000 RBX: fffffffffffffff0 RCX: ffff88003ccd30e0
[   24.995999] RDX: 0000000000000000 RSI: 0000000000000010 RDI: 0000000000000246
[   24.995999] RBP: ffff88003b595c48 R08: 0000000000000004 R09: 0000000000000000
[   24.995999] R10: 00000000e73bd78f R11: ffffffff81fe10b0 R12: 0000000000000004
[   24.995999] R13: 0000000000000001 R14: 0000000000000000 R15: 0100000000000004
[   24.995999] FS:  00007f1896b066f0(0000) GS:ffff880004a00000(0000) knlGS:0000000000000000
[   24.995999] CS:  0010 DS: 0000 ES: 0000 CR0: 000000008005003b
[   24.995999] CR2: 0000000000000000 CR3: 000000003d1f6000 CR4: 00000000000006f0
[   24.995999] DR0: 0000000000000000 DR1: 0000000000000000 DR2: 0000000000000000
[   24.995999] DR3: 0000000000000000 DR6: 00000000ffff0ff0 DR7: 0000000000000400
[   24.995999] Process S99local (pid: 3217, threadinfo ffff88003b594000, task ffff88003ccd3000)
[   24.995999] Stack:
[   24.995999]  ffffffff810bd4b2 0000000000000000 0000000104bd6280 0000000000000001
[   24.995999]  ffff880004dae3b8 ffffffff8108010f 00000000e73bd78f ffff88003b5c8000
[   24.995999]  ffff88003b5c8000 00000005d1e0b069 0000000000000001 ffff880004db4280
[   24.995999] Call Trace:
[   24.995999]  [<ffffffff810bd4b2>] ? perf_swcounter_ctx_event+0x61/0x26c
[   24.995999]  [<ffffffff8108010f>] ? trace_hardirqs_on_caller+0x12b/0x16d
[   24.995999]  [<ffffffff810bd70f>] perf_counter_task_migration+0x52/0xad
[   24.995999]  [<ffffffff810486f3>] set_task_cpu+0x174/0x1cb
[   24.995999]  [<ffffffff8106ce51>] kthread_bind+0x4b/0x9d
[   24.995999]  [<ffffffff8164bd42>] migration_call+0x76/0x50a
[   24.995999]  [<ffffffff810519f4>] ? cpu_hotplug_begin+0x35/0x77
[   24.995999]  [<ffffffff81656757>] notifier_call_chain+0x6d/0xb5
[   24.995999]  [<ffffffff810723e6>] __raw_notifier_call_chain+0x1c/0x32
[   24.995999]  [<ffffffff8164c3b5>] cpu_up+0xde/0x1b9
[   24.995999]  [<ffffffff8161ba84>] store_online+0x5a/0x9a
[   24.995999]  [<ffffffff812cb9e1>] sysdev_store+0x2e/0x44
[   24.995999]  [<ffffffff81159f39>] sysfs_write_file+0xf3/0x13c
[   24.995999]  [<ffffffff810fb410>] ? rw_verify_area+0x97/0xd1
[   24.995999]  [<ffffffff810fbdda>] vfs_write+0xbe/0x130
[   24.995999]  [<ffffffff810fbf42>] sys_write+0x56/0x93
[   24.995999]  [<ffffffff8100b502>] system_call_fastpath+0x16/0x1b
[   24.995999] Code: 4c 89 f2 48 89 df 48 f7 d8 48 89 83 28 01 00 00 48 89 83 b8 00 00 00 48 8b 4d a8 8b 75 b4 e8 ad f8 ff ff 48 8b 43 10 48 8d 58 f0 <48> 8b 43 10 0f 18 08 48 8d 43 10 48 39 45 c0 0f 85 98 fe ff ff 
[   24.995999] RIP  [<ffffffff810bd645>] perf_swcounter_ctx_event+0x1f4/0x26c

config attached.

	Ingo