Messages in this thread | | | Date | Fri, 13 Feb 2009 11:32:55 -0500 | From | Masami Hiramatsu <> | Subject | Re: irq-disabled vs vmap vs text_poke |
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Mathieu Desnoyers wrote: > * Peter Zijlstra (peterz@infradead.org) wrote: >> Hi, >> >> Ingo got the following splat: >> >> [ 5.101748] ------------[ cut here ]------------ >> [ 5.104305] WARNING: at kernel/smp.c:329 smp_call_function_many+0x34/0x1ea() >> [ 5.104305] Hardware name: P4DC6 >> [ 5.104305] Modules linked in: >> [ 5.104305] Pid: 1, comm: swapper Not tainted 2.6.29-rc4-tip-01766-g1757c19-dirty #2 >> [ 5.104305] Call Trace: >> [ 5.104305] [<c012b5d6>] warn_slowpath+0x79/0x8f >> [ 5.104305] [<c0104d24>] ? dump_trace+0x7d/0xac >> [ 5.104305] [<c014805a>] ? __lock_acquire+0x319/0x382 >> [ 5.104305] [<c014d6a1>] smp_call_function_many+0x34/0x1ea >> [ 5.104305] [<c011b59e>] ? do_flush_tlb_all+0x0/0x48 >> [ 5.104305] [<c011b59e>] ? do_flush_tlb_all+0x0/0x48 >> [ 5.104305] [<c014d878>] smp_call_function+0x21/0x28 >> [ 5.104305] [<c012fa56>] on_each_cpu+0x14/0x23 >> [ 5.104305] [<c011b56d>] flush_tlb_all+0x19/0x1b >> [ 5.104305] [<c018dcbe>] flush_tlb_kernel_range+0xd/0xf >> [ 5.104305] [<c018dd00>] vmap_debug_free_range+0x1c/0x20 >> [ 5.104305] [<c018e386>] remove_vm_area+0x28/0x67 >> [ 5.104305] [<c018e468>] __vunmap+0x30/0xab >> [ 5.104305] [<c018e50a>] vunmap+0x27/0x29 >> [ 5.104305] [<c06421b6>] text_poke+0xd6/0x104 >> [ 5.104305] [<c015687c>] ? kprobe_target+0x0/0x15 >> [ 5.104305] [<c0642a82>] arch_disarm_kprobe+0x13/0x15 >> [ 5.104305] [<c06434f9>] __unregister_kprobe_top+0x68/0xe8 >> [ 5.104305] [<c06436d2>] unregister_kretprobes+0x2c/0xb9 >> [ 5.104305] [<c0643775>] unregister_kretprobe+0x16/0x18 >> [ 5.104305] [<c0156d0b>] init_test_probes+0x2ed/0x40c >> [ 5.104305] [<c09d451c>] init_kprobes+0x127/0x131 >> [ 5.104305] [<c01476bf>] ? lock_release_holdtime+0x43/0x48 >> [ 5.104305] [<c0192e48>] ? __slab_alloc+0x5d/0x27a >> [ 5.104305] [<c0147a2a>] ? lockdep_init_map+0x80/0xe7 >> [ 5.104305] [<c0141c0d>] ? clocksource_read+0xd/0xf >> [ 5.104305] [<c0142542>] ? getnstimeofday+0x5e/0xe9 >> [ 5.104305] [<c013e01e>] ? timespec_to_ktime+0xe/0x11 >> [ 5.104305] [<c09d43f5>] ? init_kprobes+0x0/0x131 >> [ 5.104305] [<c010115c>] do_one_initcall+0x6a/0x169 >> [ 5.104305] [<c029ad2f>] ? number+0x10d/0x1cf >> [ 5.104305] [<c0147799>] ? register_lock_class+0x17/0x228 >> [ 5.104305] [<c014805a>] ? __lock_acquire+0x319/0x382 >> [ 5.104305] [<c029fa91>] ? debug_check_no_obj_freed+0xda/0x126 >> [ 5.104305] [<c014805a>] ? __lock_acquire+0x319/0x382 >> [ 5.104305] [<c01476bf>] ? lock_release_holdtime+0x43/0x48 >> [ 5.104305] [<c0640ec0>] ? _spin_unlock+0x22/0x25 >> [ 5.104305] [<c01cc0f0>] ? proc_register+0x14b/0x15c >> [ 5.104305] [<c01cc20f>] ? create_proc_entry+0x76/0x8c >> [ 5.104305] [<c0162900>] ? default_affinity_write+0x3f/0x8a >> [ 5.104305] [<c0162a6a>] ? init_irq_proc+0x58/0x65 >> [ 5.104305] [<c09bf52d>] kernel_init+0x118/0x169 >> [ 5.104305] [<c09bf415>] ? kernel_init+0x0/0x169 >> [ 5.104305] [<c0103adf>] kernel_thread_helper+0x7/0x10 >> [ 5.104305] ---[ end trace e93713a9d40cd06c ]--- >> >> Which points to vunmap() being called with interrupts disabled. >> >> Which made me look at the vmap/vunmap calls, and they appear to not be >> irq-safe, therefore this would be a bug in text_poke(). >> >> [ that is, vmap() can end up calling get_vm_area_caller() which in turn >> calls __get_vm_area_node() with GFP_KERNEL, ergo, don't do this from >> an atomic context. ] >> >> Now text_poke() uses local_irq_save/restore(), which conveys that it can >> be called with IRQs disabled, which is exactly what happens in the trace >> above, however we just established that vmap/vunmap() are not irq-safe. >> > > text_poke should actually use local_irq_disable/enable rather than > local_irq_save/restore because it _must_ be called with interrupts on.
Could you tell me why it must be called with irq on?
> >> Anybody got an idea on how to fix this? > > There is probably something wrong with the caller, kprobes, which calls > text_poke with interrupts off.
Hmm, kprobe's smoke test caused this problem. Since (un)register_kprobe() may sleep for waiting a mutex, it should not be called with interrupts off. So, it's not text_poke()'s issue nor vmap().
BTW, what about using map_vm_area() in text_poke() instead of vmap()? Since text_poke() just maps text pages to alias pages temporarily, I think we don't need to use delayed vunmap().
Thanks
> > Mathieu >
-- Masami Hiramatsu
Software Engineer Hitachi Computer Products (America) Inc. Software Solutions Division
e-mail: mhiramat@redhat.com
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