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From:   Gal Ben Haim <gbenhaim@augury.com>
Date:   Fri, 16 Nov 2018 23:36:07 +0200
Message-ID: <CAHotPr_HqPg6PrCEG2tJOa4EAvCj6SWBgJLW6JM19gwpAFd78g@mail.gmail.com>
Subject: Re: [PATCH BlueZ] io_send: Write to pipes with the MSG_NOSIGNAL flag
To:     linux-bluetooth@vger.kernel.org
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Sender: linux-bluetooth-owner@vger.kernel.org
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I did this change but it doesn't seem to write as expected, what do you think?

On Fri, Nov 16, 2018 at 10:56 PM Gal Ben-Haim <gbenhaim@augury.com> wrote:
>
> bluetoothd receives a SIGPIPE and terminates if writing to a pipe that
> was acquired by AcquireNotify and there are no readers. it can be
> reproduced by terminating the reader process without closing the reader
> end of the pipe.
>
> Requesting not to send SIGPIPE will cause the write operation to return an
> error which will be logged as "io_send: Broken pipe".
> ---
>  src/shared/io-ell.c      | 14 ++++++++++++--
>  src/shared/io-glib.c     | 15 +++++++++++++--
>  src/shared/io-mainloop.c | 14 ++++++++++++--
>  src/shared/io.h          |  2 +-
>  4 files changed, 38 insertions(+), 7 deletions(-)
>
> diff --git a/src/shared/io-ell.c b/src/shared/io-ell.c
> index 6748982c7..2bd166966 100644
> --- a/src/shared/io-ell.c
> +++ b/src/shared/io-ell.c
> @@ -117,7 +117,7 @@ bool io_set_disconnect_handler(struct io *io, io_callback_func_t callback,
>                                                         user_data, destroy);
>  }
>
> -ssize_t io_send(struct io *io, const struct iovec *iov, int iovcnt)
> +ssize_t io_send(struct io *io, struct iovec *iov, int iovcnt)
>  {
>         ssize_t ret;
>         int fd;
> @@ -129,8 +129,18 @@ ssize_t io_send(struct io *io, const struct iovec *iov, int iovcnt)
>         if (fd < 0)
>                 return -ENOTCONN;
>
> +       const struct msghdr msg = {
> +                .msg_name = NULL,
> +                .msg_namelen = 0,
> +                .msg_iov = iov,
> +                .msg_iovlen = iovcnt,
> +                .msg_control = NULL,
> +                .msg_controllen = 0,
> +                .msg_flags = 0
> +        };
> +
>         do {
> -               ret = writev(fd, iov, iovcnt);
> +               ret = sendmsg(fd, &msg, MSG_NOSIGNAL);
>         } while (ret < 0 && errno == EINTR);
>
>         if (ret < 0)
> diff --git a/src/shared/io-glib.c b/src/shared/io-glib.c
> index d62de4e10..7e4c9961b 100644
> --- a/src/shared/io-glib.c
> +++ b/src/shared/io-glib.c
> @@ -26,6 +26,7 @@
>  #endif
>
>  #include <errno.h>
> +#include <sys/socket.h>
>
>  #include <glib.h>
>
> @@ -263,7 +264,7 @@ bool io_set_disconnect_handler(struct io *io, io_callback_func_t callback,
>         return io_set_handler(io, G_IO_HUP, callback, user_data, destroy);
>  }
>
> -ssize_t io_send(struct io *io, const struct iovec *iov, int iovcnt)
> +ssize_t io_send(struct io *io, struct iovec *iov, int iovcnt)
>  {
>         int fd;
>         ssize_t ret;
> @@ -273,8 +274,18 @@ ssize_t io_send(struct io *io, const struct iovec *iov, int iovcnt)
>
>         fd = io_get_fd(io);
>
> +       const struct msghdr msg = {
> +                .msg_name = NULL,
> +                .msg_namelen = 0,
> +                .msg_iov = iov,
> +                .msg_iovlen = iovcnt,
> +                .msg_control = NULL,
> +                .msg_controllen = 0,
> +                .msg_flags = 0
> +        };
> +
>         do {
> -               ret = writev(fd, iov, iovcnt);
> +               ret = sendmsg(fd, &msg, MSG_NOSIGNAL);
>         } while (ret < 0 && errno == EINTR);
>
>         if (ret < 0)
> diff --git a/src/shared/io-mainloop.c b/src/shared/io-mainloop.c
> index 2306c3479..4b6cc14c7 100644
> --- a/src/shared/io-mainloop.c
> +++ b/src/shared/io-mainloop.c
> @@ -298,15 +298,25 @@ bool io_set_disconnect_handler(struct io *io, io_callback_func_t callback,
>         return true;
>  }
>
> -ssize_t io_send(struct io *io, const struct iovec *iov, int iovcnt)
> +ssize_t io_send(struct io *io, struct iovec *iov, int iovcnt)
>  {
>         ssize_t ret;
>
>         if (!io || io->fd < 0)
>                 return -ENOTCONN;
>
> +       const struct msghdr msg = {
> +               .msg_name = NULL,
> +               .msg_namelen = 0,
> +               .msg_iov = iov,
> +               .msg_iovlen = iovcnt,
> +               .msg_control = NULL,
> +               .msg_controllen = 0,
> +               .msg_flags = 0
> +       };
> +
>         do {
> -               ret = writev(io->fd, iov, iovcnt);
> +               ret = sendmsg(io->fd, &msg, MSG_NOSIGNAL);
>         } while (ret < 0 && errno == EINTR);
>
>         if (ret < 0)
> diff --git a/src/shared/io.h b/src/shared/io.h
> index 8bc1111d0..522ec26ff 100644
> --- a/src/shared/io.h
> +++ b/src/shared/io.h
> @@ -34,7 +34,7 @@ void io_destroy(struct io *io);
>  int io_get_fd(struct io *io);
>  bool io_set_close_on_destroy(struct io *io, bool do_close);
>
> -ssize_t io_send(struct io *io, const struct iovec *iov, int iovcnt);
> +ssize_t io_send(struct io *io, struct iovec *iov, int iovcnt);
>  bool io_shutdown(struct io *io);
>
>  typedef bool (*io_callback_func_t)(struct io *io, void *user_data);
> --
> 2.19.1
>