scsi: ipr: Fix scsi-mq lockdep issue

Fixes the following lockdep warning that can occur when scsi-mq is
enabled with ipr due to ipr calling scsi_unblock_requests from irq
context. The fix is to move the call to scsi_unblock_requests to ipr's
existing workqueue.

stack backtrace:
CPU: 28 PID: 0 Comm: swapper/28 Not tainted 4.13.0-rc2-gcc6x-gf74c89b #1
Call Trace:
[c000001fffe97550] [c000000000b50818] dump_stack+0xe8/0x160 (unreliable)
[c000001fffe97590] [c0000000001586d0] print_usage_bug+0x2d0/0x390
[c000001fffe97640] [c000000000158f34] mark_lock+0x7a4/0x8e0
[c000001fffe976f0] [c00000000015a000] __lock_acquire+0x6a0/0x1a70
[c000001fffe97860] [c00000000015befc] lock_acquire+0xec/0x2e0
[c000001fffe97930] [c000000000b71514] _raw_spin_lock+0x44/0x70
[c000001fffe97960] [c0000000005b60f4] blk_mq_sched_dispatch_requests+0xa4/0x2a0
[c000001fffe979c0] [c0000000005acac0] __blk_mq_run_hw_queue+0x100/0x2c0
[c000001fffe97a00] [c0000000005ad478] __blk_mq_delay_run_hw_queue+0x118/0x130
[c000001fffe97a40] [c0000000005ad61c] blk_mq_start_hw_queues+0x6c/0xa0
[c000001fffe97a80] [c000000000797aac] scsi_kick_queue+0x2c/0x60
[c000001fffe97aa0] [c000000000797cf0] scsi_run_queue+0x210/0x360
[c000001fffe97b10] [c00000000079b888] scsi_run_host_queues+0x48/0x80
[c000001fffe97b40] [c0000000007b6090] ipr_ioa_bringdown_done+0x70/0x1e0
[c000001fffe97bc0] [c0000000007bc860] ipr_reset_ioa_job+0x80/0xf0
[c000001fffe97bf0] [c0000000007b4d50] ipr_reset_timer_done+0xd0/0x100
[c000001fffe97c30] [c0000000001937bc] call_timer_fn+0xdc/0x4b0
[c000001fffe97cf0] [c000000000193d08] expire_timers+0x178/0x330
[c000001fffe97d60] [c0000000001940c8] run_timer_softirq+0xb8/0x120
[c000001fffe97de0] [c000000000b726a8] __do_softirq+0x168/0x6d8
[c000001fffe97ef0] [c0000000000df2c8] irq_exit+0x108/0x150
[c000001fffe97f10] [c000000000017bf4] __do_irq+0x2a4/0x4a0
[c000001fffe97f90] [c00000000002da50] call_do_irq+0x14/0x24
[c0000007fad93aa0] [c000000000017e8c] do_IRQ+0x9c/0x140
[c0000007fad93af0] [c000000000008b98] hardware_interrupt_common+0x138/0x140

Reported-by: Michael Ellerman <mpe@ellerman.id.au>
Signed-off-by: Brian King <brking@linux.vnet.ibm.com>
Signed-off-by: Martin K. Petersen <martin.petersen@oracle.com>

2 files changed, 21 insertions, 14 deletions

diff --git a/drivers/scsi/ipr.c b/drivers/scsi/ipr.c
index b0c68d24db01..da5bdbdcce52 100644
--- a/drivers/scsi/ipr.c
+++ b/drivers/scsi/ipr.c
@@ -3351,6 +3351,16 @@ static void ipr_worker_thread(struct work_struct *work)
                 return;
         }
 
+        if (ioa_cfg->scsi_unblock) {
+                ioa_cfg->scsi_unblock = 0;
+                ioa_cfg->scsi_blocked = 0;
+                spin_unlock_irqrestore(ioa_cfg->host->host_lock, lock_flags);
+                scsi_unblock_requests(ioa_cfg->host);
+                spin_lock_irqsave(ioa_cfg->host->host_lock, lock_flags);
+                if (ioa_cfg->scsi_blocked)
+                        scsi_block_requests(ioa_cfg->host);
+        }
+
         if (!ioa_cfg->scan_enabled) {
                 spin_unlock_irqrestore(ioa_cfg->host->host_lock, lock_flags);
                 return;
@@ -7211,9 +7221,8 @@ static int ipr_ioa_bringdown_done(struct ipr_cmnd *ipr_cmd)
         ENTER;
         if (!ioa_cfg->hrrq[IPR_INIT_HRRQ].removing_ioa) {
                 ipr_trace;
-                spin_unlock_irq(ioa_cfg->host->host_lock);
-                scsi_unblock_requests(ioa_cfg->host);
-                spin_lock_irq(ioa_cfg->host->host_lock);
+                ioa_cfg->scsi_unblock = 1;
+                schedule_work(&ioa_cfg->work_q);
         }
 
         ioa_cfg->in_reset_reload = 0;
@@ -7287,13 +7296,7 @@ static int ipr_ioa_reset_done(struct ipr_cmnd *ipr_cmd)
         list_add_tail(&ipr_cmd->queue, &ipr_cmd->hrrq->hrrq_free_q);
         wake_up_all(&ioa_cfg->reset_wait_q);
 
-        spin_unlock(ioa_cfg->host->host_lock);
-        scsi_unblock_requests(ioa_cfg->host);
-        spin_lock(ioa_cfg->host->host_lock);
-
-        if (!ioa_cfg->hrrq[IPR_INIT_HRRQ].allow_cmds)
-                scsi_block_requests(ioa_cfg->host);
-
+        ioa_cfg->scsi_unblock = 1;
         schedule_work(&ioa_cfg->work_q);
         LEAVE;
         return IPR_RC_JOB_RETURN;
@@ -9249,8 +9252,11 @@ static void _ipr_initiate_ioa_reset(struct ipr_ioa_cfg *ioa_cfg,
                 spin_unlock(&ioa_cfg->hrrq[i]._lock);
         }
         wmb();
-        if (!ioa_cfg->hrrq[IPR_INIT_HRRQ].removing_ioa)
+        if (!ioa_cfg->hrrq[IPR_INIT_HRRQ].removing_ioa) {
+                ioa_cfg->scsi_unblock = 0;
+                ioa_cfg->scsi_blocked = 1;
                 scsi_block_requests(ioa_cfg->host);
+        }
 
         ipr_cmd = ipr_get_free_ipr_cmnd(ioa_cfg);
         ioa_cfg->reset_cmd = ipr_cmd;
@@ -9306,9 +9312,8 @@ static void ipr_initiate_ioa_reset(struct ipr_ioa_cfg *ioa_cfg,
                         wake_up_all(&ioa_cfg->reset_wait_q);
 
                         if (!ioa_cfg->hrrq[IPR_INIT_HRRQ].removing_ioa) {
-                                spin_unlock_irq(ioa_cfg->host->host_lock);
-                                scsi_unblock_requests(ioa_cfg->host);
-                                spin_lock_irq(ioa_cfg->host->host_lock);
+                                ioa_cfg->scsi_unblock = 1;
+                                schedule_work(&ioa_cfg->work_q);
                         }
                         return;
                 } else {
diff --git a/drivers/scsi/ipr.h b/drivers/scsi/ipr.h
index e98a87a65335..c7f0e9e3cd7d 100644
--- a/drivers/scsi/ipr.h
+++ b/drivers/scsi/ipr.h
@@ -1488,6 +1488,8 @@ struct ipr_ioa_cfg {
         u8 cfg_locked:1;
         u8 clear_isr:1;
         u8 probe_done:1;
+        u8 scsi_unblock:1;
+        u8 scsi_blocked:1;
 
         u8 revid;