Oh my, sent it with a wrong subject, sorry - the kernel in question i
2.6.31-rc4-rt1:

Hi,

I'm getting a bunch of BUGs, one from Xorg on startup and lots from
jackd. So far they don't seem to carry any ill-effects.

[   15.323439] BUG: sleeping function called from invalid context at
arch/x86/mm/highmem_32.c:9
[   15.323449] in_atomic(): 1, irqs_disabled(): 0, pid: 2462, name: Xorg
[   15.323457] Pid: 2462, comm: Xorg Not tainted 2.6.31-rc4-rt1 #1
[   15.323463] Call Trace:
[   15.323478]  [<c10262bf>] ? kmap+0x4f/0x60
[   15.323530]  [<f828f86f>] ? i915_gem_pwrite_ioctl+0x79f/0x8f0 [i915]
[   15.323542]  [<c10cec1e>] ? _slab_irq_disable+0x3e/0x60
[   15.323592]  [<f80c400f>] ? drm_gem_handle_create+0x6f/0x90 [drm]
[   15.323602]  [<c1294ac5>] ? rt_mutex_lock+0x15/0x50
[   15.323646]  [<f80c26fd>] ? drm_ioctl+0x15d/0x340 [drm]
[   15.323687]  [<f828f0d0>] ? i915_gem_pwrite_ioctl+0x0/0x8f0 [i915]
[   15.323698]  [<c116249f>] ? cpumask_any_but+0x1f/0x30
[   15.323706]  [<c102548c>] ? flush_tlb_page+0x5c/0xc0
[   15.323713]  [<c1024b02>] ? ptep_set_access_flags+0x42/0x60
[   15.323721]  [<c1294ac5>] ? rt_mutex_lock+0x15/0x50
[   15.323730]  [<c10664c6>] ? rt_down+0x16/0x50
[   15.323751]  [<c10e25af>] ? vfs_ioctl+0x7f/0x90
[   15.323759]  [<c10e2723>] ? do_vfs_ioctl+0x73/0x670
[   15.323768]  [<c10bcb5c>] ? handle_mm_fault+0x51c/0x730
[   15.323778]  [<c10d5339>] ? vfs_write+0x129/0x190
[   15.323787]  [<c10e2da4>] ? sys_ioctl+0x84/0x90
[   15.323795]  [<c1003a8c>] ? sysenter_do_call+0x12/0x28

... (unrelated) ...

[   68.633271] BUG: using smp_processor_id() in preemptible [00000000]
code: jackd/3322
[   68.633287] caller is __schedule+0xc/0xa00
[   68.633295] Pid: 3322, comm: jackd Not tainted 2.6.31-rc4-rt1 #1
[   68.633301] Call Trace:
[   68.633314]  [<c116f091>] ? debug_smp_processor_id+0xc1/0xd0
[   68.633323]  [<c1292b9c>] ? __schedule+0xc/0xa00
[   68.633335]  [<c105ccc4>] ? getnstimeofday+0x54/0x110
[   68.633344]  [<c116af12>] ? copy_to_user+0x42/0x130
[   68.633353]  [<c1056220>] ? hrtimer_get_res+0x0/0x30
[   68.633362]  [<c10515a4>] ? sys_clock_gettime+0x54/0xc0
[   68.633371]  [<c1003c0a>] ? work_resched+0x5/0x19
[   98.488299] BUG: using smp_processor_id() in preemptible [00000000]
code: jackd/3321
[   98.488315] caller is __schedule+0xc/0xa00
[   98.488323] Pid: 3321, comm: jackd Not tainted 2.6.31-rc4-rt1 #1
[   98.488329] Call Trace:
[   98.488341]  [<c116f091>] ? debug_smp_processor_id+0xc1/0xd0
[   98.488351]  [<c1292b9c>] ? __schedule+0xc/0xa00
[   98.488361]  [<c1061089>] ? tick_program_event+0x39/0x50
[   98.488371]  [<c1040366>] ? wakeup_softirqd+0x16/0x60
[   98.488381]  [<c1088d44>] ? rcu_irq_exit+0x14/0x90
[   98.488389]  [<c1041485>] ? irq_exit+0x35/0x80
[   98.488398]  [<c1017e83>] ? smp_apic_timer_interrupt+0x53/0x80
[   98.488408]  [<c1003c0a>] ? work_resched+0x5/0x19
[  108.743612] BUG: using smp_processor_id() in preemptible [00000000]
code: jackd/3322
[  108.743629] caller is __schedule+0xc/0xa00
[  108.743637] Pid: 3322, comm: jackd Not tainted 2.6.31-rc4-rt1 #1
[  108.743643] Call Trace:
[  108.743657]  [<c116f091>] ? debug_smp_processor_id+0xc1/0xd0
[  108.743667]  [<c1292b9c>] ? __schedule+0xc/0xa00
[  108.743678]  [<c105ccc4>] ? getnstimeofday+0x54/0x110
[  108.743687]  [<c116af12>] ? copy_to_user+0x42/0x130
[  108.743696]  [<c1056220>] ? hrtimer_get_res+0x0/0x30
[  108.743704]  [<c10515a4>] ? sys_clock_gettime+0x54/0xc0
[  108.743714]  [<c1003c0a>] ? work_resched+0x5/0x19
[  172.293274] BUG: using smp_processor_id() in preemptible [00000000]
code: jackd/3322
[  172.293292] caller is __schedule+0xc/0xa00
[  172.293300] Pid: 3322, comm: jackd Not tainted 2.6.31-rc4-rt1 #1
[  172.293305] Call Trace:
[  172.293318]  [<c116f091>] ? debug_smp_processor_id+0xc1/0xd0
[  172.293328]  [<c1292b9c>] ? __schedule+0xc/0xa00
[  172.293340]  [<c105ccc4>] ? getnstimeofday+0x54/0x110
[  172.293349]  [<c116af12>] ? copy_to_user+0x42/0x130
[  172.293358]  [<c1056220>] ? hrtimer_get_res+0x0/0x30
[  172.293366]  [<c10515a4>] ? sys_clock_gettime+0x54/0xc0
[  172.293376]  [<c1003c0a>] ? work_resched+0x5/0x19

... (more of the same) ...

Dunno if that means anything to you but if you need any more info
please CC me as I'm not subscribed.

Cheers,
koniu