[PR] imx9/lpuart: Fix race condition / regression in imx9_txint [nuttx]

["jlaitine (via GitHub)" <gi...@apache.org>]

jlaitine opened a new pull request, #16654:
URL: https://github.com/apache/nuttx/pull/16654

   ## Summary
   
   Commit 83a119160 fixed SMP by removing call to uart_xmitchars from inside spinlock.
   
   This only works for SMP, since uart_xmitchars has a lock only in SMP and the irq lock is ifdeffed away in a single-core system: https://github.com/apache/nuttx/blob/3d37e85b13fb57ae8f1b8f6917e5aaac918d0982/drivers/serial/serial_io.c#L61 . 
   
   Thus, in a single-core configuration the uart_xmitchars can now be called in parallel from the interrupt handler and from the imx9_txint.
   
   Fix this by filling the uart buffers already before enabling the interrupt, this way it is not possible to get the function called in parallel for the same device.
   
   ## Impact
   
   Fixes a regression in lpuart for single-core configuration, due to SMP enabling.
   
   ## Testing
   
   Tested on a custom imx93 based device
   


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Re: [PR] imx9/lpuart: Fix race condition / regression in imx9_txint [nuttx]

["acassis (via GitHub)" <gi...@apache.org>]

acassis merged PR #16654:
URL: https://github.com/apache/nuttx/pull/16654


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