From 8a2bb5917850d9caf0d5984531b745668450dd6f Mon Sep 17 00:00:00 2001 From: Alexander Graf Date: Thu, 1 Apr 2010 17:36:23 +0200 Subject: [PATCH] Make char muxer more robust wrt small FIFOs Virtio-Console can only process one character at a time. Using it on S390 gave me strage "lags" where I got the character I pressed before when pressing one. So I typed in "abc" and only received "a", then pressed "d" but the guest received "b" and so on. While the stdio driver calls a poll function that just processes on its queue in case virtio-console can't take multiple characters at once, the muxer does not have such callbacks, so it can't empty its queue. To work around that limitation, I introduced a new timer that only gets active when the guest can not receive any more characters. In that case it polls again after a while to check if the guest is now receiving input. This patch fixes input when using -nographic on s390 for me. --- qemu-char.c | 16 ++++++++++++++++ 1 file changed, 16 insertions(+) diff --git a/qemu-char.c b/qemu-char.c index cff2896..206bd07 100644 --- a/qemu-char.c +++ b/qemu-char.c @@ -260,6 +260,9 @@ typedef struct { IOEventHandler *chr_event[MAX_MUX]; void *ext_opaque[MAX_MUX]; CharDriverState *drv; +#if defined(TARGET_S390X) + QEMUTimer *accept_timer; +#endif int focus; int mux_cnt; int term_got_escape; @@ -416,6 +419,15 @@ static void mux_chr_accept_input(CharDriverState *chr) d->chr_read[m](d->ext_opaque[m], &d->buffer[m][d->cons[m]++ & MUX_BUFFER_MASK], 1); } + +#if defined(TARGET_S390X) + /* We're still not able to sync producer and consumer, so let's wait a bit + and try again by then. */ + if (d->prod[m] != d->cons[m]) { + qemu_mod_timer(d->accept_timer, qemu_get_clock_ns(vm_clock) + + (int64_t)100000); + } +#endif } static int mux_chr_can_read(void *opaque) @@ -498,6 +510,10 @@ static CharDriverState *qemu_chr_open_mux(CharDriverState *drv) chr->opaque = d; d->drv = drv; d->focus = -1; +#if defined(TARGET_S390X) + d->accept_timer = qemu_new_timer_ns(vm_clock, + (QEMUTimerCB*)mux_chr_accept_input, chr); +#endif chr->chr_write = mux_chr_write; chr->chr_update_read_handler = mux_chr_update_read_handler; chr->chr_accept_input = mux_chr_accept_input;