Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1756530Ab3GYVdQ (ORCPT ); Thu, 25 Jul 2013 17:33:16 -0400 Received: from mail-ea0-f169.google.com ([209.85.215.169]:35938 "EHLO mail-ea0-f169.google.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1755942Ab3GYVdM (ORCPT ); Thu, 25 Jul 2013 17:33:12 -0400 Date: Thu, 25 Jul 2013 23:33:02 +0200 (CEST) From: John Kacur To: linux-kernel@vger.kernel.org, "Stephen M. Cameron" cc: "James E.J. Bottomley" , "Luis Claudio R. Goncalves" , Clark Williams , linux-rt-users@vger.kernel.org Subject: hpsa - BUG: using smp_processor_id() in preemptible [00000000 00000000] code: kworker/u:0/6 Message-ID: User-Agent: Alpine 2.03 (LFD 1266 2009-07-14) MIME-Version: 1.0 Content-Type: TEXT/PLAIN; charset=US-ASCII Sender: linux-kernel-owner@vger.kernel.org List-ID: X-Mailing-List: linux-kernel@vger.kernel.org Content-Length: 4006 Lines: 93 Hi We're seeing this on a 3.6 kernel with the real-time patch applied, but it looks like it is relevant with the real-time patch in the latest kernel too. [ 49.688847] hpsa 0000:03:00.0: hpsa0: <0x323a> at IRQ 67 using DAC [ 49.749928] scsi0 : hpsa [ 49.784437] BUG: using smp_processor_id() in preemptible [00000000 00000000] code: kworker/u:0/6 [ 49.784465] caller is enqueue_cmd_and_start_io+0x5a/0x100 [hpsa] [ 49.784468] Pid: 6, comm: kworker/u:0 Not tainted 3.6.11.5-rt37.52.el6rt.x86_64.debug #1 [ 49.784471] Call Trace: [ 49.784512] [] debug_smp_processor_id+0x123/0x150 [ 49.784520] [] enqueue_cmd_and_start_io+0x5a/0x100 [hpsa] [ 49.784529] [] hpsa_scsi_do_simple_cmd_core+0xeb/0x110 [hpsa] [ 49.784537] [] ? swiotlb_dma_mapping_error+0x18/0x30 [ 49.784544] [] ? swiotlb_dma_mapping_error+0x18/0x30 [ 49.784553] [] hpsa_scsi_do_simple_cmd_with_retry+0x91/0x280 [hpsa] [ 49.784562] [] hpsa_scsi_do_report_luns.clone.2+0xd8/0x130 [hpsa] [ 49.784571] [] hpsa_gather_lun_info.clone.3+0x3a/0x1a0 [hpsa] [ 49.784580] [] hpsa_update_scsi_devices+0x11f/0x4f0 [hpsa] [ 49.784592] [] ? sub_preempt_count+0xa9/0xe0 [ 49.784601] [] hpsa_scan_start+0xfd/0x150 [hpsa] [ 49.784613] [] ? rt_spin_lock_slowunlock+0x78/0x90 [ 49.784626] [] do_scsi_scan_host+0x37/0xa0 [ 49.784632] [] do_scan_async+0x1a/0x30 [ 49.784643] [] async_run_entry_fn+0x9b/0x1d0 [ 49.784655] [] process_one_work+0x1f2/0x620 [ 49.784661] [] ? process_one_work+0x180/0x620 [ 49.784668] [] ? worker_thread+0x5e/0x3a0 [ 49.784674] [] ? async_schedule+0x20/0x20 [ 49.784681] [] worker_thread+0x133/0x3a0 [ 49.784688] [] ? manage_workers+0x190/0x190 [ 49.784696] [] kthread+0xa6/0xb0 [ 49.784707] [] kernel_thread_helper+0x4/0x10 [ 49.784715] [] ? finish_task_switch+0x8c/0x110 [ 49.784721] [] ? _raw_spin_unlock_irq+0x3b/0x70 [ 49.784727] [] ? retint_restore_args+0xe/0xe [ 49.784734] [] ? kthreadd+0x1e0/0x1e0 [ 49.784739] [] ? gs_change+0xb/0xb ------- When I look at the code I see this call chain enqueue_cmd_and_start_io()-> set_performant_mode()-> smp_processor_id() Which if you have debugging enabled calls debug_processor_id() and triggers the warning. I'm not very familiar with the hpsa code, so I'm not entirely sure what the purpose of this line is c->Header.ReplyQueue = smp_processor_id() % h->nreply_queues; Is the purpose to simply try to get a range of ReplyQueue numbers, but somewhat arbitrary? Or is it necessary that the current processor_id is used? If it is the former, and you're not accessing per cpu structures, or pinning a cpu, or anything like that then I would think it is safe to change this to a raw_smp_processor_id() to get rid of a false positive warning. diff --git a/drivers/scsi/hpsa.c b/drivers/scsi/hpsa.c index 7f4f790..4e19267 100644 --- a/drivers/scsi/hpsa.c +++ b/drivers/scsi/hpsa.c @@ -583,7 +583,7 @@ static void set_performant_mode(struct ctlr_info *h, struct CommandList *c) c->busaddr |= 1 | (h->blockFetchTable[c->Header.SGList] << 1); if (likely(h->msix_vector)) c->Header.ReplyQueue = - smp_processor_id() % h->nreply_queues; + raw_smp_processor_id() % h->nreply_queues; } } Thanks John Kacur -- To unsubscribe from this list: send the line "unsubscribe linux-kernel" in the body of a message to majordomo@vger.kernel.org More majordomo info at http://vger.kernel.org/majordomo-info.html Please read the FAQ at http://www.tux.org/lkml/