Commit 34689e20 authored by Paolo Bonzini's avatar Paolo Bonzini
Browse files

qemu-char: Keep pty slave file descriptor open until the master is closed 



If a process opens the slave pts device, writes data to it, then
immediately closes it, the data doesn't reliably get delivered to the
emulated serial port. This seems to be because a read of the master
pty device returns EIO on Linux if no process has the pts device open,
even when data is waiting "in the pipe".

A fix seems to be for QEMU to keep the pts file descriptor open until
the pty is closed, as per the below patch.

Signed-off-by: default avatarAshley Jonathan <jonathan.ashley@altran.com>
Message-Id: <AC19797808C8D548ABDE0CA4A97AA30A30DEB409@XMB-DCFR-37.europe.corp.altran.com>
Reviewed-by: default avatarMichael Tokarev <mjt@tls.msk.ru>
Signed-off-by: default avatarPaolo Bonzini <pbonzini@redhat.com>
parent 5b82b703

qemu-char.c

+3 −1
Original line number Diff line number Diff line
@@ -1171,6 +1171,7 @@ typedef struct { 
    int connected;

    guint timer_tag;

    guint open_tag;

    int slave_fd;

} PtyCharDriver;



static void pty_chr_update_read_handler_locked(CharDriverState *chr);
@@ -1347,6 +1348,7 @@ static void pty_chr_close(struct CharDriverState *chr) 


    qemu_mutex_lock(&chr->chr_write_lock);

    pty_chr_state(chr, 0);

    close(s->slave_fd);

    object_unref(OBJECT(s->ioc));

    if (s->timer_tag) {

        g_source_remove(s->timer_tag);
@@ -1374,7 +1376,6 @@ static CharDriverState *qemu_chr_open_pty(const char *id, 
        return NULL;

    }



    close(slave_fd);

    qemu_set_nonblock(master_fd);



    chr = qemu_chr_alloc(common, errp);
@@ -1399,6 +1400,7 @@ static CharDriverState *qemu_chr_open_pty(const char *id, 
    chr->explicit_be_open = true;



    s->ioc = QIO_CHANNEL(qio_channel_file_new_fd(master_fd));

    s->slave_fd = slave_fd;

    s->timer_tag = 0;



    return chr;