linux-kernel - [PATCH v2] dmaengine: dmatest: fix timeout caused by kthread

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Date: Thu, 25 Apr 2024 20:40:38 +0800
From: Jie Hai <haijie1@...wei.com>
To: <vkoul@...nel.org>, "open list:DMA GENERIC OFFLOAD ENGINE SUBSYSTEM"
	<dmaengine@...r.kernel.org>, open list <linux-kernel@...r.kernel.org>
CC: <dmaengine@...r.kernel.org>, <linux-kernel@...r.kernel.org>
Subject: [PATCH v2] dmaengine: dmatest: fix timeout caused by kthread_stop

The change introduced by commit a7c01fa93aeb ("signal: break
out of wait loops on kthread_stop()") may cause dmatest aborts
any ongoing tests and possible failure on the tests.

The operations are as follows:
  modprobe hisi_dma
  modprobe dmatest
  echo 0 > /sys/module/dmatest/parameters/iterations
  echo "dma0chan0" > /sys/module/dmatest/parameters/channel
  echo "dma0chan1" > /sys/module/dmatest/parameters/channel
  echo "dma0chan2" > /sys/module/dmatest/parameters/channel
  echo 1 > /sys/module/dmatest/parameters/run
  echo 0 > /sys/module/dmatest/parameters/run

And the failed dmesg logs are:
  [52575.636992] dmatest: Added 1 threads using dma0chan0
  [52575.637555] dmatest: Added 1 threads using dma0chan1
  [52575.638044] dmatest: Added 1 threads using dma0chan2
  [52581.020355] dmatest: Started 1 threads using dma0chan0
  [52581.020585] dmatest: Started 1 threads using dma0chan1
  [52581.020814] dmatest: Started 1 threads using dma0chan2
  [52587.705782] dmatest: dma0chan0-copy0: result #57691: 'test \
    timed out' with src_off=0xfe6 dst_off=0x89 len=0x1d9a (0)
  [52587.706527] dmatest: dma0chan0-copy0: summary 57691 tests, \
    1 failures 51179.98 iops 411323 KB/s (0)
  [52587.707028] dmatest: dma0chan1-copy0: result #63178: 'test \
    timed out' with src_off=0xdf dst_off=0x6ab len=0x389e (0)
  [52587.707767] dmatest: dma0chan1-copy0: summary 63178 tests, \
    1 failures 62851.60 iops 503835 KB/s (0)
  [52587.708376] dmatest: dma0chan2-copy0: result #60527: 'test \
    timed out' with src_off=0x10e dst_off=0x58 len=0x3ea4 (0)
  [52587.708951] dmatest: dma0chan2-copy0: summary 60527 tests, \
    1 failures 52403.78 iops 420014 KB/s (0)

The test 57691 of dma0chan0-copy0 does not time out, it is the
signal brought by kthread_stop() interrupted the function
wait_event_freezable_timeout() waiting for test completing.
The timeout log is misleading and the ongoing test can be
completed if wait_event_freezable_timeout() is replaced by
wait_event_timeout().

Signed-off-by: Jie Hai <haijie1@...wei.com>
---
v2:
1. Add more details in commit log.
---
 drivers/dma/dmatest.c | 2 +-
 1 file changed, 1 insertion(+), 1 deletion(-)

diff --git a/drivers/dma/dmatest.c b/drivers/dma/dmatest.c
index a4f608837849..854165f55e7b 100644
--- a/drivers/dma/dmatest.c
+++ b/drivers/dma/dmatest.c
@@ -841,7 +841,7 @@ static int dmatest_func(void *data)
 		} else {
 			dma_async_issue_pending(chan);
 
-			wait_event_freezable_timeout(thread->done_wait,
+			ret = wait_event_timeout(thread->done_wait,
 					done->done,
 					msecs_to_jiffies(params->timeout));
 
-- 
2.30.0