[PATCH] spi: lantiq-ssc: Fix warning by using WQ_MEM_RECLAIM

[PATCH] spi: lantiq-ssc: Fix warning by using WQ_MEM_RECLAIM

[Hauke Mehrtens]

The lantiq-ssc driver uses internally an own workqueue to wait till the
data is not only written out of the FIFO but really written to the wire.
This workqueue is flushed while the SPI subsystem is working in some
other system workqueue.

The system workqueue is marked as WQ_MEM_RECLAIM, but the workqueue in
the lantiq-ssc driver does not use WQ_MEM_RECLAIM for now. Add this flag
too to prevent this warning.

This fixes the following warning:
[    2.972635] ------------[ cut here ]------------
[    2.975956] WARNING: CPU: 1 PID: 17 at kernel/workqueue.c:2614 check_flush_dependency+0x168/0x184
[    2.984752] workqueue: WQ_MEM_RECLAIM kblockd:blk_mq_run_work_fn is flushing !WQ_MEM_RECLAIM 1e100800.spi:0x0
[    2.984759] Modules linked in:
[    2.997686] CPU: 1 PID: 17 Comm: kworker/1:0H Not tainted 5.4.51 #0
[    3.003927] Workqueue: kblockd blk_mq_run_work_fn
[    3.008610] Stack : 80662c88 83c75794 806e0000 80730000 83c1de80 806744ac 80045888 00000009
[    3.016965]         83fb6510 83d779b4 83e81e00 8007b6d4 00000001 00000001 83c75750 760d28ee
[    3.025321]         00000000 00000000 00000000 00000096 6b5f666e 00000000 5f72756e 5f776f72
[    3.033677]         00000096 808b0000 00000000 00000f57 00000000 80750000 00000000 80045888
[    3.042032]         00000009 83fb6510 83d779b4 83e81e00 00000000 00000010 00000004 80880004
[    3.050388]         ...
[    3.052828] Call Trace:
[    3.055281] [<8000f5d0>] show_stack+0x30/0x100
[    3.059754] [<8057bb14>] dump_stack+0x9c/0xd4
[    3.064096] [<8002cf1c>] __warn+0xc0/0x10c
[    3.068170] [<8002cff4>] warn_slowpath_fmt+0x8c/0xac
[    3.073137] [<80045888>] check_flush_dependency+0x168/0x184
[    3.078701] [<800459b4>] flush_workqueue+0x110/0x624
[    3.083680] [<803b50a0>] lantiq_ssc_unprepare_message+0x18/0x40
[    3.089582] [<803b2290>] spi_finalize_current_message+0x168/0x220
[    3.095674] [<803b2550>] spi_transfer_one_message+0x208/0x4cc
[    3.101418] [<803b2b4c>] __spi_pump_messages+0x338/0x540
[    3.106727] [<803b2f74>] __spi_sync+0x214/0x240
[    3.111253] [<803b2fd0>] spi_sync+0x30/0x58
[    3.115432] [<803b3f50>] spi_mem_exec_op+0x2a8/0x404
[    3.120413] [<803947e4>] spi_nor_spimem_xfer_data+0xa4/0x118
[    3.126052] [<803948cc>] spi_nor_spimem_read_data+0x74/0x80
[    3.131622] [<803959e0>] spi_nor_read+0x110/0x1d0
[    3.136324] [<8036fd44>] part_read+0x60/0xb8
[    3.140585] [<8036ce4c>] mtd_read_oob+0xe8/0x100
[    3.145198] [<8036cea0>] mtd_read+0x3c/0x54
[    3.149384] [<803772c8>] mtdblock_readsect+0x58/0x17c
[    3.154426] [<80376ca4>] mtd_queue_rq+0x408/0x5ac
[    3.159141] [<80286c44>] blk_mq_dispatch_rq_list+0x150/0x67c
[    3.164787] [<8028cdbc>] blk_mq_sched_dispatch_requests+0x1ac/0x1c8
[    3.171051] [<80284434>] __blk_mq_run_hw_queue+0x148/0x208
[    3.176543] [<80046870>] process_one_work+0x238/0x48c
[    3.181582] [<80046c2c>] worker_thread+0x168/0x5e0
[    3.186371] [<8004c404>] kthread+0x138/0x140
[    3.190641] [<8000a658>] ret_from_kernel_thread+0x14/0x1c
[    3.196092] ---[ end trace c03c86833514b76d ]---

Fixes: 891b7c5fbf61 ("mtd_blkdevs: convert to blk-mq")
Signed-off-by: Hauke Mehrtens <hauke@hauke-m.de>
---
 drivers/spi/spi-lantiq-ssc.c | 2 +-
 1 file changed, 1 insertion(+), 1 deletion(-)

diff --git a/drivers/spi/spi-lantiq-ssc.c b/drivers/spi/spi-lantiq-ssc.c
index 1fd7ee53d451..a12a5d0cfebf 100644
--- a/drivers/spi/spi-lantiq-ssc.c
+++ b/drivers/spi/spi-lantiq-ssc.c
@@ -899,7 +899,7 @@ static int lantiq_ssc_probe(struct platform_device *pdev)
 	master->bits_per_word_mask = SPI_BPW_RANGE_MASK(2, 8) |
 				     SPI_BPW_MASK(16) | SPI_BPW_MASK(32);
 
-	spi->wq = alloc_ordered_workqueue(dev_name(dev), 0);
+	spi->wq = alloc_ordered_workqueue(dev_name(dev), WQ_MEM_RECLAIM);
 	if (!spi->wq) {
 		err = -ENOMEM;
 		goto err_clk_put;
-- 
2.20.1

Re: [PATCH] spi: lantiq-ssc: Fix warning by using WQ_MEM_RECLAIM

[Mark Brown]

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On Wed, Jul 15, 2020 at 01:02:34AM +0200, Hauke Mehrtens wrote:

> This fixes the following warning:
> [    2.972635] ------------[ cut here ]------------
> [    2.975956] WARNING: CPU: 1 PID: 17 at kernel/workqueue.c:2614 check_flush_dependency+0x168/0x184
> [    2.984752] workqueue: WQ_MEM_RECLAIM kblockd:blk_mq_run_work_fn is flushing !WQ_MEM_RECLAIM 1e100800.spi:0x0
> [    2.984759] Modules linked in:

Please think hard before including complete backtraces in upstream
reports, they are very large and contain almost no useful information
relative to their size so often obscure the relevant content in your
message. If part of the backtrace is usefully illustrative (it often is
for search engines if nothing else) then it's usually better to pull out
the relevant sections.

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Re: [PATCH] spi: lantiq-ssc: Fix warning by using WQ_MEM_RECLAIM

[Hauke Mehrtens]

[-- Attachment #1.1: Type: text/plain, Size: 930 bytes --]

On 7/15/20 11:48 AM, Mark Brown wrote:
> On Wed, Jul 15, 2020 at 01:02:34AM +0200, Hauke Mehrtens wrote:
> 
>> This fixes the following warning:
>> [    2.972635] ------------[ cut here ]------------
>> [    2.975956] WARNING: CPU: 1 PID: 17 at kernel/workqueue.c:2614 check_flush_dependency+0x168/0x184
>> [    2.984752] workqueue: WQ_MEM_RECLAIM kblockd:blk_mq_run_work_fn is flushing !WQ_MEM_RECLAIM 1e100800.spi:0x0
>> [    2.984759] Modules linked in:
> 
> Please think hard before including complete backtraces in upstream
> reports, they are very large and contain almost no useful information
> relative to their size so often obscure the relevant content in your
> message. If part of the backtrace is usefully illustrative (it often is
> for search engines if nothing else) then it's usually better to pull out
> the relevant sections.
> 
Ok, I will send a v2 with an updated commit message.

Hauke


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