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stm32f4: UART DMA causes lockup in xtimer_drift test #4716

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jnohlgard opened this issue Jan 29, 2016 · 2 comments
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stm32f4: UART DMA causes lockup in xtimer_drift test #4716

jnohlgard opened this issue Jan 29, 2016 · 2 comments
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@haukepetersen
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Platform: ARM Platform: This PR/issue effects ARM-based platforms Type: bug The issue reports a bug / The PR fixes a bug (including spelling errors)

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@jnohlgard
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Current tests/xtimer_drift in master does not run for me on stm32f4discovery, it hangs after trying to start the first slacker thread.
Disabling DMA in the UART TX by commenting out code seem to make the problem go away.

I suspect there is a race between the main thread using printf/puts right before the thread_create call and the newly created thread also using printf immediately after creation.
@jnohlgard jnohlgard added Type: bug The issue reports a bug / The PR fixes a bug (including spelling errors) Platform: ARM Platform: This PR/issue effects ARM-based platforms labels Jan 29, 2016
@OlegHahm
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Related to #4488?

@jnohlgard
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no, after looking into this a bit further it seems like the problem is that periph/uart is not thread safe, it is just that we have not seen any symptoms until DMA was implemented in a driver.

jnohlgard pushed a commit to jnohlgard/RIOT that referenced this issue Jan 30, 2016
cpu/stm32f4: Fix DMA race bug (RIOT-OS#4716)
fa3ccc0
jnohlgard pushed a commit to jnohlgard/RIOT that referenced this issue Jan 30, 2016
cpu/stm32f4: Fix DMA race bug (RIOT-OS#4716)
4fd7f23
This was referenced Jan 30, 2016
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jnohlgard pushed a commit that referenced this issue Feb 1, 2016
Merge pull request #4717 from gebart/pr/stm32f4-uart-lock
fa273b1 
cpu/stm32f4: Fix DMA race bug (#4716)
@jnohlgard jnohlgard mentioned this issue Feb 4, 2016
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lebrush pushed a commit to lebrush/RIOT that referenced this issue Jun 27, 2016
cpu/stm32f4: Fix DMA race bug (RIOT-OS#4716)
e43f5bd
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