This reverts commit 67c5322d7000fd105a926eec44bc1765b7d70bdd:
I'm not sure if the retry logic has ever worked when not using FIFO mode.
I
found this while writing a test case although code inspection confirms it
is
definitely broken.
The TSR retry logic will never actually happen because it is guarded by an
'if (s->tsr_rety > 0)' but this is the only place that can ever make the
variable greater than zero. That effectively makes the retry logic an 'if
(0)
I believe this is a typo and the intention was >= 0. Once this is fixed
thoug
I see double transmits with my test case. This is because in the non FIFO
case, serial_xmit may get invoked while LSR.THRE is still high because the
character was processed but the retransmit timer was still active.
We can handle this by simply checking for LSR.THRE and returning early.
It's
possible that the FIFO paths also need some attention.
Cc: Stefano Stabellini <address@hidden>
Signed-off-by: Anthony Liguori <address@hidden>
Even if the previous logic was never worked, new logic breaks stuff -
namely,
qemu -enable-kvm -nographic -kernel /boot/vmlinuz-$(uname -r) -append
console=ttyS0 -serial pty
the above command will cause the virtual machine to stuck at startup
using 100% CPU till one connects to the pty and sends any char to it.
Note this is rather typical invocation for various headless virtual
machines by libvirt.
So revert this change for now, till a better solution will be found.
Signed-off-by: Michael Tokarev <address@hidden>
---
hw/serial.c | 4 +---
1 file changed, 1 insertion(+), 3 deletions(-)
diff --git a/hw/serial.c b/hw/serial.c
index a421d1e..df54de2 100644
--- a/hw/serial.c
+++ b/hw/serial.c
@@ -327,8 +327,6 @@ static void serial_xmit(void *opaque)
s->tsr = fifo_get(s,XMIT_FIFO);
if (!s->xmit_fifo.count)
s->lsr |= UART_LSR_THRE;
- } else if ((s->lsr & UART_LSR_THRE)) {
- return;
} else {
s->tsr = s->thr;
s->lsr |= UART_LSR_THRE;
@@ -340,7 +338,7 @@ static void serial_xmit(void *opaque)
/* in loopback mode, say that we just received a char */
serial_receive1(s, &s->tsr, 1);
} else if (qemu_chr_fe_write(s->chr, &s->tsr, 1) != 1) {
- if ((s->tsr_retry >= 0) && (s->tsr_retry <= MAX_XMIT_RETRY)) {
+ if ((s->tsr_retry > 0) && (s->tsr_retry <= MAX_XMIT_RETRY)) {
s->tsr_retry++;
qemu_mod_timer(s->transmit_timer, new_xmit_ts +
s->char_transmit_time);
return;