From 804a5cb526c121226830c686132b1b82aa12b76c Mon Sep 17 00:00:00 2001 From: John Kacur Date: Fri, 26 Jul 2013 16:06:18 +0200 Subject: [PATCH] [SCSI] hpsa: fix warning with smp_processor_id() in preemptible section Signed-off-by: John Kacur On a 3.6-rt (real-time patch) kernel we are seeing the following BUG However, it appears to be relevant for non-realtime (mainline) as well. [ 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 ------------------- This is caused by 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. The code here is c->Header.ReplyQueue = smp_processor_id() % h->nreply_queues; Since it is not critical that the code complete on the same processor, but the cpu is a hint used in generating the ReplyQueue and will still work if the cpu migrates or is preempted, it is safe to use the raw_smp_processor_id() to surpress the false positve warning. Signed-off-by: John Kacur Acked-by: Stephen Cameron Signed-off-by: James Bottomley --- drivers/scsi/hpsa.c | 2 +- 1 file changed, 1 insertion(+), 1 deletion(-) diff --git a/drivers/scsi/hpsa.c b/drivers/scsi/hpsa.c index e631bcd2742..b766f5aea58 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; } } -- 2.41.0