From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1758053AbZBMMs3 (ORCPT ); Fri, 13 Feb 2009 07:48:29 -0500 Received: (majordomo@vger.kernel.org) by vger.kernel.org id S1752283AbZBMMsV (ORCPT ); Fri, 13 Feb 2009 07:48:21 -0500 Received: from bombadil.infradead.org ([18.85.46.34]:36172 "EHLO bombadil.infradead.org" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1751599AbZBMMsU (ORCPT ); Fri, 13 Feb 2009 07:48:20 -0500 Subject: irq-disabled vs vmap vs text_poke From: Peter Zijlstra To: Nick Piggin , akpm , Mathieu Desnoyers Cc: linux-kernel , Ingo Molnar Content-Type: text/plain Content-Transfer-Encoding: 7bit Date: Fri, 13 Feb 2009 13:50:07 +0100 Message-Id: <1234529407.6519.28.camel@twins> Mime-Version: 1.0 X-Mailer: Evolution 2.24.3 Sender: linux-kernel-owner@vger.kernel.org List-ID: X-Mailing-List: linux-kernel@vger.kernel.org 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] [] warn_slowpath+0x79/0x8f [ 5.104305] [] ? dump_trace+0x7d/0xac [ 5.104305] [] ? __lock_acquire+0x319/0x382 [ 5.104305] [] smp_call_function_many+0x34/0x1ea [ 5.104305] [] ? do_flush_tlb_all+0x0/0x48 [ 5.104305] [] ? do_flush_tlb_all+0x0/0x48 [ 5.104305] [] smp_call_function+0x21/0x28 [ 5.104305] [] on_each_cpu+0x14/0x23 [ 5.104305] [] flush_tlb_all+0x19/0x1b [ 5.104305] [] flush_tlb_kernel_range+0xd/0xf [ 5.104305] [] vmap_debug_free_range+0x1c/0x20 [ 5.104305] [] remove_vm_area+0x28/0x67 [ 5.104305] [] __vunmap+0x30/0xab [ 5.104305] [] vunmap+0x27/0x29 [ 5.104305] [] text_poke+0xd6/0x104 [ 5.104305] [] ? kprobe_target+0x0/0x15 [ 5.104305] [] arch_disarm_kprobe+0x13/0x15 [ 5.104305] [] __unregister_kprobe_top+0x68/0xe8 [ 5.104305] [] unregister_kretprobes+0x2c/0xb9 [ 5.104305] [] unregister_kretprobe+0x16/0x18 [ 5.104305] [] init_test_probes+0x2ed/0x40c [ 5.104305] [] init_kprobes+0x127/0x131 [ 5.104305] [] ? lock_release_holdtime+0x43/0x48 [ 5.104305] [] ? __slab_alloc+0x5d/0x27a [ 5.104305] [] ? lockdep_init_map+0x80/0xe7 [ 5.104305] [] ? clocksource_read+0xd/0xf [ 5.104305] [] ? getnstimeofday+0x5e/0xe9 [ 5.104305] [] ? timespec_to_ktime+0xe/0x11 [ 5.104305] [] ? init_kprobes+0x0/0x131 [ 5.104305] [] do_one_initcall+0x6a/0x169 [ 5.104305] [] ? number+0x10d/0x1cf [ 5.104305] [] ? register_lock_class+0x17/0x228 [ 5.104305] [] ? __lock_acquire+0x319/0x382 [ 5.104305] [] ? debug_check_no_obj_freed+0xda/0x126 [ 5.104305] [] ? __lock_acquire+0x319/0x382 [ 5.104305] [] ? lock_release_holdtime+0x43/0x48 [ 5.104305] [] ? _spin_unlock+0x22/0x25 [ 5.104305] [] ? proc_register+0x14b/0x15c [ 5.104305] [] ? create_proc_entry+0x76/0x8c [ 5.104305] [] ? default_affinity_write+0x3f/0x8a [ 5.104305] [] ? init_irq_proc+0x58/0x65 [ 5.104305] [] kernel_init+0x118/0x169 [ 5.104305] [] ? kernel_init+0x0/0x169 [ 5.104305] [] 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. Anybody got an idea on how to fix this?