From: 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. |hpsa 0000:03:00.0: hpsa0: <0x323a> at IRQ 67 using DAC |scsi0 : hpsa |BUG: using smp_processor_id() in preemptible [0000000000000000] code: kworker/u:0/6 |caller is enqueue_cmd_and_start_io+0x5a/0x100 [hpsa] |Pid: 6, comm: kworker/u:0 Not tainted 3.6.11.5-rt37.52.el6rt.x86_64.debug #1 |Call Trace: | [] debug_smp_processor_id+0x123/0x150 | [] enqueue_cmd_and_start_io+0x5a/0x100 [hpsa] | [] hpsa_scsi_do_simple_cmd_core+0xeb/0x110 [hpsa] | [] ? swiotlb_dma_mapping_error+0x18/0x30 | [] ? swiotlb_dma_mapping_error+0x18/0x30 | [] hpsa_scsi_do_simple_cmd_with_retry+0x91/0x280 [hpsa] | [] hpsa_scsi_do_report_luns.clone.2+0xd8/0x130 [hpsa] | [] hpsa_gather_lun_info.clone.3+0x3a/0x1a0 [hpsa] | [] hpsa_update_scsi_devices+0x11f/0x4f0 [hpsa] | [] ? sub_preempt_count+0xa9/0xe0 | [] hpsa_scan_start+0xfd/0x150 [hpsa] | [] ? rt_spin_lock_slowunlock+0x78/0x90 | [] do_scsi_scan_host+0x37/0xa0 | [] do_scan_async+0x1a/0x30 | [] async_run_entry_fn+0x9b/0x1d0 | [] process_one_work+0x1f2/0x620 | [] ? process_one_work+0x180/0x620 | [] ? worker_thread+0x5e/0x3a0 | [] ? async_schedule+0x20/0x20 | [] worker_thread+0x133/0x3a0 | [] ? manage_workers+0x190/0x190 | [] kthread+0xa6/0xb0 | [] kernel_thread_helper+0x4/0x10 | [] ? finish_task_switch+0x8c/0x110 | [] ? _raw_spin_unlock_irq+0x3b/0x70 | [] ? retint_restore_args+0xe/0xe | [] ? kthreadd+0x1e0/0x1e0 | [] ? 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. Cc: stable-rt@vger.kernel.org Signed-off-by: John Kacur Acked-by: Stephen Signed-off-by: Sebastian Andrzej Siewior --- 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 f9823f2..be83a15 100644 --- a/drivers/scsi/hpsa.c +++ b/drivers/scsi/hpsa.c @@ -565,7 +565,7 @@ 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; } } -- 1.7.10.4 -- 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/