raiden00pl commented on code in PR #20030:
URL: https://github.com/apache/nuttx/pull/20030#discussion_r3955448443
##########
drivers/serial/serial_io.c:
##########
@@ -57,24 +57,32 @@
void uart_xmitchars(FAR uart_dev_t *dev)
{
uint16_t nbytes = 0;
+ sbuf_size_t head;
#ifdef CONFIG_SMP
irqstate_t flags = enter_critical_section();
#endif
- /* Send while we still have data in the TX buffer & room in the fifo */
+ /* Send while we still have data in the TX buffer & room in the fifo.
+ *
+ * uart_putxmitchar() advances xmit.head from thread context without
+ * holding the critical section, so on SMP it can move (and wrap) while
Review Comment:
the producer writes head outside any lock. This ring is a
single-producer/single-consumer ring:
https://github.com/apache/nuttx/blob/35e8eebff3a1e04cb55943351f339353e81f6653/drivers/serial/serial.c#L279-L286
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