Re: [PATCH] ipr: Fix scsi-mq lockdep issue

[Martin K. Petersen]

Brian,

> 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.

Applied to 4.13/scsi-fixes. Thank you!

-- 
Martin K. Petersen  Oracle Linux Engineering

[PATCH] ipr: Fix scsi-mq lockdep issue

[Brian King]

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:
[c01fffe97550] [c0b50818] dump_stack+0xe8/0x160 (unreliable)
[c01fffe97590] [c01586d0] print_usage_bug+0x2d0/0x390
[c01fffe97640] [c0158f34] mark_lock+0x7a4/0x8e0
[c01fffe976f0] [c015a000] __lock_acquire+0x6a0/0x1a70
[c01fffe97860] [c015befc] lock_acquire+0xec/0x2e0
[c01fffe97930] [c0b71514] _raw_spin_lock+0x44/0x70
[c01fffe97960] [c05b60f4] blk_mq_sched_dispatch_requests+0xa4/0x2a0
[c01fffe979c0] [c05acac0] __blk_mq_run_hw_queue+0x100/0x2c0
[c01fffe97a00] [c05ad478] __blk_mq_delay_run_hw_queue+0x118/0x130
[c01fffe97a40] [c05ad61c] blk_mq_start_hw_queues+0x6c/0xa0
[c01fffe97a80] [c0797aac] scsi_kick_queue+0x2c/0x60
[c01fffe97aa0] [c0797cf0] scsi_run_queue+0x210/0x360
[c01fffe97b10] [c079b888] scsi_run_host_queues+0x48/0x80
[c01fffe97b40] [c07b6090] ipr_ioa_bringdown_done+0x70/0x1e0
[c01fffe97bc0] [c07bc860] ipr_reset_ioa_job+0x80/0xf0
[c01fffe97bf0] [c07b4d50] ipr_reset_timer_done+0xd0/0x100
[c01fffe97c30] [c01937bc] call_timer_fn+0xdc/0x4b0
[c01fffe97cf0] [c0193d08] expire_timers+0x178/0x330
[c01fffe97d60] [c01940c8] run_timer_softirq+0xb8/0x120
[c01fffe97de0] [c0b726a8] __do_softirq+0x168/0x6d8
[c01fffe97ef0] [c00df2c8] irq_exit+0x108/0x150
[c01fffe97f10] [c0017bf4] __do_irq+0x2a4/0x4a0
[c01fffe97f90] [c002da50] call_do_irq+0x14/0x24
[c007fad93aa0] [c0017e8c] do_IRQ+0x9c/0x140
[c007fad93af0] [c0008b98] hardware_interrupt_common+0x138/0x140

Reported-by: Michael Ellerman 
Signed-off-by: Brian King 
---

Index: linux-2.6.git/drivers/scsi/ipr.c
===
--- linux-2.6.git.orig/drivers/scsi/ipr.c
+++ linux-2.6.git/drivers/scsi/ipr.c
@@ -3351,6 +3351,16 @@ static void ipr_worker_thread(struct wor
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
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(_cfg->work_q);
}
 
ioa_cfg->in_reset_reload = 0;
@@ -7287,13 +7296,7 @@ static int ipr_ioa_reset_done(struct ipr
list_add_tail(_cmd->queue, _cmd->hrrq->hrrq_free_q);
wake_up_all(_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(_cfg->work_q);
LEAVE;
return IPR_RC_JOB_RETURN;
@@ -9249,8 +9252,11 @@ static void _ipr_initiate_ioa_reset(stru
spin_unlock(_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(struc
wake_up_all(_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;
+