Re: [Qemu-trivial] [PATCH] Keep pty slave file descriptor open until the master is closed

[Michael Tokarev <mjt@tls.msk.ru>]

11.12.2015 14:29, Ashley Jonathan wrote:
> I have experienced a minor difficulty using QEMU with the "-serial pty" option:
> 
> 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.

The patch looks fine, so

Reviewed-by: Michael Tokarev <mjt@tls.msk.ru>

but I'd love to have an ACK from the maintainer about this one,
or for it to pick it up.

Thanks,

/mjt

> ---
>  qemu-char.c | 4 +++-
>  1 file changed, 3 insertions(+), 1 deletion(-)
> 
> diff --git a/qemu-char.c b/qemu-char.c
> index 2969c44..ed03ba0 100644
> --- a/qemu-char.c
> +++ b/qemu-char.c
> @@ -1198,6 +1198,7 @@ typedef struct {
>      int connected;
>      guint timer_tag;
>      guint open_tag;
> +    int slave_fd;
>  } PtyCharDriver;
>  
>  static void pty_chr_update_read_handler_locked(CharDriverState *chr);
> @@ -1373,6 +1374,7 @@ static void pty_chr_close(struct CharDriverState *chr)
>  
>      qemu_mutex_lock(&chr->chr_write_lock);
>      pty_chr_state(chr, 0);
> +    close(s->slave_fd);
>      fd = g_io_channel_unix_get_fd(s->fd);
>      g_io_channel_unref(s->fd);
>      close(fd);
> @@ -1401,7 +1403,6 @@ static CharDriverState *qemu_chr_open_pty(const char *id,
>          return NULL;
>      }
>  
> -    close(slave_fd);
>      qemu_set_nonblock(master_fd);
>  
>      chr = qemu_chr_alloc();
> @@ -1422,6 +1423,7 @@ static CharDriverState *qemu_chr_open_pty(const char *id,
>      chr->explicit_be_open = true;
>  
>      s->fd = io_channel_from_fd(master_fd);
> +    s->slave_fd = slave_fd;
>      s->timer_tag = 0;
>  
>      return chr;
>