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qemu-char: simplify pty polling 

There is no need to use a timer and pty_chr_read to detect a connected
pty.  It is simpler to just call g_poll periodically and check for POLLHUP.
It is done once per second, and only if the pty is disconnected, so it
is cheap enough.

Tested with "-monitor pty" and "-serial mon:pty", both of which work
correctly and do not freeze QEMU.  (How to test ptys?  "socat -,raw,echo=0
/dev/pts/4,raw").

Signed-off-by: Paolo Bonzini <pbonzini@redhat.com>
Message-id: 1366385529-10329-3-git-send-email-pbonzini@redhat.com
Signed-off-by: Anthony Liguori <aliguori@us.ibm.com>
This commit is contained in:
Paolo Bonzini 2013-04-19 17:32:07 +02:00 committed by Anthony Liguori
parent 910b63682e
commit 85a67692d0
1 changed files with 17 additions and 24 deletions
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41
qemu-char.c
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@ -1028,7 +1028,6 @@ typedef struct {
GIOChannel *fd;
guint fd_tag;
int connected;
int polling;
int read_bytes;
guint timer_tag;
} PtyCharDriver;
@ -1044,12 +1043,6 @@ static gboolean pty_chr_timer(gpointer opaque)
if (s->connected) {
goto out;
}
if (s->polling) {
/* If we arrive here without polling being cleared due
* read returning -EIO, then we are (re-)connected */
pty_chr_state(chr, 1);
goto out;
}
/* Next poll ... */
pty_chr_update_read_handler(chr);
@ -1128,22 +1121,17 @@ static gboolean pty_chr_read(GIOChannel *chan, GIOCondition cond, void *opaque)
static void pty_chr_update_read_handler(CharDriverState *chr)
{
PtyCharDriver *s = chr->opaque;
GPollFD pfd;
if (s->fd_tag) {
g_source_remove(s->fd_tag);
pfd.fd = g_io_channel_unix_get_fd(s->fd);
pfd.events = G_IO_OUT;
pfd.revents = 0;
g_poll(&pfd, 1, 0);
if (pfd.revents & G_IO_HUP) {
pty_chr_state(chr, 0);
} else {
pty_chr_state(chr, 1);
}
s->fd_tag = io_add_watch_poll(s->fd, pty_chr_read_poll, pty_chr_read, chr);
s->polling = 1;
/*
* Short timeout here: just need wait long enougth that qemu makes
* it through the poll loop once. When reconnected we want a
* short timeout so we notice it almost instantly. Otherwise
* read() gives us -EIO instantly, making pty_chr_state() reset the
* timeout to the normal (much longer) poll interval before the
* timer triggers.
*/
pty_chr_rearm_timer(chr, 10);
}
static void pty_chr_state(CharDriverState *chr, int connected)
@ -1156,15 +1144,20 @@ static void pty_chr_state(CharDriverState *chr, int connected)
s->fd_tag = 0;
}
s->connected = 0;
s->polling = 0;
/* (re-)connect poll interval for idle guests: once per second.
* We check more frequently in case the guests sends data to
* the virtual device linked to our pty. */
pty_chr_rearm_timer(chr, 1000);
} else {
if (!s->connected)
if (s->timer_tag) {
g_source_remove(s->timer_tag);
s->timer_tag = 0;
}
if (!s->connected) {
qemu_chr_be_generic_open(chr);
s->connected = 1;
s->connected = 1;
s->fd_tag = io_add_watch_poll(s->fd, pty_chr_read_poll, pty_chr_read, chr);
}
}
}