| From: John Kacur <jkacur@redhat.com> |
| Date: Fri, 26 Jul 2013 16:06:18 +0200 |
| Subject: [PATCH] hpsa: fix warning with smp_processor_id() in preemptible |
| section |
| |
| 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: |
| | [<ffffffff812abe83>] debug_smp_processor_id+0x123/0x150 |
| | [<ffffffffa009043a>] enqueue_cmd_and_start_io+0x5a/0x100 [hpsa] |
| | [<ffffffffa00905cb>] hpsa_scsi_do_simple_cmd_core+0xeb/0x110 [hpsa] |
| | [<ffffffff812b09c8>] ? swiotlb_dma_mapping_error+0x18/0x30 |
| | [<ffffffff812b09c8>] ? swiotlb_dma_mapping_error+0x18/0x30 |
| | [<ffffffffa0090701>] hpsa_scsi_do_simple_cmd_with_retry+0x91/0x280 [hpsa] |
| | [<ffffffffa0093558>] hpsa_scsi_do_report_luns.clone.2+0xd8/0x130 [hpsa] |
| | [<ffffffffa00935ea>] hpsa_gather_lun_info.clone.3+0x3a/0x1a0 [hpsa] |
| | [<ffffffffa00963df>] hpsa_update_scsi_devices+0x11f/0x4f0 [hpsa] |
| | [<ffffffff81592019>] ? sub_preempt_count+0xa9/0xe0 |
| | [<ffffffffa00968ad>] hpsa_scan_start+0xfd/0x150 [hpsa] |
| | [<ffffffff8158cba8>] ? rt_spin_lock_slowunlock+0x78/0x90 |
| | [<ffffffff813b04d7>] do_scsi_scan_host+0x37/0xa0 |
| | [<ffffffff813b05da>] do_scan_async+0x1a/0x30 |
| | [<ffffffff8107c4ab>] async_run_entry_fn+0x9b/0x1d0 |
| | [<ffffffff8106ae92>] process_one_work+0x1f2/0x620 |
| | [<ffffffff8106ae20>] ? process_one_work+0x180/0x620 |
| | [<ffffffff8106d4fe>] ? worker_thread+0x5e/0x3a0 |
| | [<ffffffff8107c410>] ? async_schedule+0x20/0x20 |
| | [<ffffffff8106d5d3>] worker_thread+0x133/0x3a0 |
| | [<ffffffff8106d4a0>] ? manage_workers+0x190/0x190 |
| | [<ffffffff81073236>] kthread+0xa6/0xb0 |
| | [<ffffffff815970a4>] kernel_thread_helper+0x4/0x10 |
| | [<ffffffff81082a7c>] ? finish_task_switch+0x8c/0x110 |
| | [<ffffffff8158e44b>] ? _raw_spin_unlock_irq+0x3b/0x70 |
| | [<ffffffff8158e85d>] ? retint_restore_args+0xe/0xe |
| | [<ffffffff81073190>] ? kthreadd+0x1e0/0x1e0 |
| | [<ffffffff815970a0>] ? 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 <jkacur@redhat.com> |
| Acked-by: Stephen <scameron@beardog.cce.hp.com> |
| Signed-off-by: Sebastian Andrzej Siewior <bigeasy@linutronix.de> |
| --- |
| drivers/scsi/hpsa.c | 2 +- |
| 1 file changed, 1 insertion(+), 1 deletion(-) |
| |
| --- a/drivers/scsi/hpsa.c |
| +++ b/drivers/scsi/hpsa.c |
| @@ -583,7 +583,7 @@ static void set_performant_mode(struct 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; |
| } |
| } |
| |