Commit 85a67692 authored by Paolo Bonzini's avatar Paolo Bonzini Committed by Anthony Liguori
Browse files

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: default avatarPaolo Bonzini <pbonzini@redhat.com>
Message-id: 1366385529-10329-3-git-send-email-pbonzini@redhat.com
Signed-off-by: default avatarAnthony Liguori <aliguori@us.ibm.com>
parent 910b6368

qemu-char.c

+17 −24
Original line number Diff line number Diff line
@@ -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->fd_tag = io_add_watch_poll(s->fd, pty_chr_read_poll, pty_chr_read, chr);

        }

    }

}