linux-kernel - [PATCH] dmaengine: dmatest: Don't forcibly terminate channel in polled mode

lists.openwall.net		lists / announce owl-users owl-dev john-users john-dev passwdqc-users yescrypt popa3d-users / oss-security kernel-hardening musl sabotage tlsify passwords / crypt-dev xvendor / Bugtraq Full-Disclosure linux-kernel linux-netdev linux-ext4 linux-hardening linux-cve-announce PHC
Open Source and information security mailing list archives

Hash Suite for Android: free password hash cracker in your pocket

[<prev] [next>] [day] [month] [year] [list]

Message-Id: <20250408-dmaengine-dmatest-poll-mode-fix-v1-1-754a446a5363@amd.com>
Date: Tue, 08 Apr 2025 08:37:49 -0500
From: Nathan Lynch via B4 Relay <devnull+nathan.lynch.amd.com@...nel.org>
To: Vinod Koul <vkoul@...nel.org>
Cc: Péter Ujfalusi <peter.ujfalusi@...il.com>, 
 Vinicius Costa Gomes <vinicius.gomes@...el.com>, 
 Dave Jiang <dave.jiang@...el.com>, dmaengine@...r.kernel.org, 
 linux-kernel@...r.kernel.org, Nathan Lynch <nathan.lynch@....com>
Subject: [PATCH] dmaengine: dmatest: Don't forcibly terminate channel in
 polled mode

From: Nathan Lynch <nathan.lynch@....com>

Invoking dmaengine_terminate_sync() against the channel after each
submitted descriptor is strange. It's benign when the test is
single-threaded, but disruptive when multiple threads are submitting
descriptors to the channel concurrently:

  # cd /sys/module/dmatest/parameters/
  # echo 1 > polled
  # echo 2 > threads_per_chan
  # echo dma0chan0 > channel
  # echo 1 > run
...
  dmatest: Added 2 threads using dma0chan0
  dmatest: Started 2 threads using dma0chan0
  xilinx-zynqmp-dma ffa80000.dma: dma_sync_wait: timeout!
  xilinx-zynqmp-dma ffa80000.dma: dma_sync_wait: timeout!
  dmatest: dma0chan0-copy0: result #3: 'test timed out' with
    src_off=0x487 dst_off=0xf8 len=0x171b (0)
  dmatest: dma0chan0-copy1: result #6: 'test timed out' with
    src_off=0x227d dst_off=0xf99 len=0xf7a (0)

Remove the call to dmaengine_terminate_sync() from the main thread
loop.

Fixes: fb9816f9d05f ("dmaengine: dmatest: Add support for completion polling")
Signed-off-by: Nathan Lynch <nathan.lynch@....com>
---
 drivers/dma/dmatest.c | 1 -
 1 file changed, 1 deletion(-)

diff --git a/drivers/dma/dmatest.c b/drivers/dma/dmatest.c
index d891dfca358e209c9a5c2d8b49e3e539130e53e8..4e109c45fe0c5a7e8f337efe6e00e0616977f770 100644
--- a/drivers/dma/dmatest.c
+++ b/drivers/dma/dmatest.c
@@ -835,7 +835,6 @@ static int dmatest_func(void *data)
 
 		if (params->polled) {
 			status = dma_sync_wait(chan, cookie);
-			dmaengine_terminate_sync(chan);
 			if (status == DMA_COMPLETE)
 				done->done = true;
 		} else {

---
base-commit: 0af2f6be1b4281385b618cb86ad946eded089ac8
change-id: 20250403-dmaengine-dmatest-poll-mode-fix-671b02dc9084

Best regards,
-- 
Nathan Lynch <nathan.lynch@....com>