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fix uart.c to work with UART_TX_BUF_SIZE == 1

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This commit is contained in:
Robert Morris 2020-10-20 07:02:44 -04:00
parent 55ad99f729
commit 4df1a265cb
1 changed files with 7 additions and 7 deletions
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14
kernel/uart.c
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@ -42,8 +42,8 @@
struct spinlock uart_tx_lock;
#define UART_TX_BUF_SIZE 32
char uart_tx_buf[UART_TX_BUF_SIZE];
int uart_tx_w; // write next to uart_tx_buf[uart_tx_w++]
int uart_tx_r; // read next from uart_tx_buf[uar_tx_r++]
uint64 uart_tx_w; // write next to uart_tx_buf[uart_tx_w % UART_TX_BUF_SIZE]
uint64 uart_tx_r; // read next from uart_tx_buf[uar_tx_r % UART_TX_BUF_SIZE]
extern volatile int panicked; // from printf.c
@ -94,13 +94,13 @@ uartputc(int c)
}
while(1){
if(((uart_tx_w + 1) % UART_TX_BUF_SIZE) == uart_tx_r){
if(uart_tx_w == uart_tx_r + UART_TX_BUF_SIZE){
// buffer is full.
// wait for uartstart() to open up space in the buffer.
sleep(&uart_tx_r, &uart_tx_lock);
} else {
uart_tx_buf[uart_tx_w] = c;
uart_tx_w = (uart_tx_w + 1) % UART_TX_BUF_SIZE;
uart_tx_buf[uart_tx_w % UART_TX_BUF_SIZE] = c;
uart_tx_w += 1;
uartstart();
release(&uart_tx_lock);
return;
@ -150,8 +150,8 @@ uartstart()
return;
}
int c = uart_tx_buf[uart_tx_r];
uart_tx_r = (uart_tx_r + 1) % UART_TX_BUF_SIZE;
int c = uart_tx_buf[uart_tx_r % UART_TX_BUF_SIZE];
uart_tx_r += 1;
// maybe uartputc() is waiting for space in the buffer.
wakeup(&uart_tx_r);