From: Sergio Lopez Date: Tue, 5 Jun 2018 07:54:55 +0000 (-0400) Subject: hw/char/serial: Only retry if qemu_chr_fe_write returns 0 X-Git-Url: http://git.maquefel.me/?a=commitdiff_plain;h=019288bf137183bf3407c9824655b753bfafc99f;p=qemu.git hw/char/serial: Only retry if qemu_chr_fe_write returns 0 Only retry on serial_xmit if qemu_chr_fe_write returns 0, as this is the only recoverable error. Retrying with any other scenario, in addition to being a waste of CPU cycles, can compromise the Guest stability if by the vCPU issuing the write and the main loop thread are, by chance or explicit pinning, running on the same pCPU. Previous discussion: https://lists.nongnu.org/archive/html/qemu-devel/2018-05/msg06998.html Signed-off-by: Sergio Lopez Message-Id: <1528185295-14199-1-git-send-email-slp@redhat.com> Signed-off-by: Paolo Bonzini --- diff --git a/hw/char/serial.c b/hw/char/serial.c index 605b0d02f9..6de6c29779 100644 --- a/hw/char/serial.c +++ b/hw/char/serial.c @@ -260,7 +260,7 @@ static void serial_xmit(SerialState *s) if (s->mcr & UART_MCR_LOOP) { /* 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 && + } else if (qemu_chr_fe_write(&s->chr, &s->tsr, 1) == 0 && s->tsr_retry < MAX_XMIT_RETRY) { assert(s->watch_tag == 0); s->watch_tag =