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ASoC: SOF: trace: sdev->host_offset management changes#3516

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plbossart merged 2 commits into
thesofproject:topic/sof-devfrom
ujfalusi:peter/sof/pr/dtrace_print_offsets_01
May 20, 2022
Merged

ASoC: SOF: trace: sdev->host_offset management changes#3516
plbossart merged 2 commits into
thesofproject:topic/sof-devfrom
ujfalusi:peter/sof/pr/dtrace_print_offsets_01

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@ujfalusi

@ujfalusi ujfalusi commented Mar 14, 2022

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Hi,

The READ_ONCE(sdev->host_offset) alone does nothing to prevent any race regarding to host_offset change race prevention.
Introduce a new helper to do this in a correct way and while at it, print out the new offset for us to see where we are.

Additional debug prints can be added to track what is copied to user space with a simple change:

diff --git a/sound/soc/sof/trace.c b/sound/soc/sof/trace.c
index 76c763da5804..32c3c0d8a75e 100644
--- a/sound/soc/sof/trace.c
+++ b/sound/soc/sof/trace.c
@@ -334,8 +334,10 @@ static ssize_t sof_dfsentry_trace_read(struct file *file, char __user *buffer,
 	}
 
 	/* no new trace data */
-	if (!avail)
+	if (!avail) {
+		dev_dbg(sdev->dev, "trace: nothing to copy\n");
 		return 0;
+	}
 
 	/* make sure count is <= avail */
 	if (count > avail)
@@ -349,6 +351,8 @@ static ssize_t sof_dfsentry_trace_read(struct file *file, char __user *buffer,
 	 */
 	snd_dma_buffer_sync(&sdev->dmatb, SNDRV_DMA_SYNC_CPU);
 	/* copy available trace data to debugfs */
+	dev_dbg(sdev->dev, "trace: copy to user from offset : %#llx, count: %#zx\n",
+		lpos, count);
 	rem = copy_to_user(buffer, ((u8 *)(dfse->buf) + lpos), count);
 	if (rem)
 		return -EFAULT;

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@plbossart plbossart plbossart approved these changes

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3 participants

@ujfalusi @plbossart @bardliao