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Bug 626748 – Use async methods for writing and handle EAGAIN

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If sending a lot of data and/or the other peer is not reading it, then
socket buffers can overflow. This is communicated from the kernel by
returning EAGAIN. In GIO, it is modelled by g_output_stream_write()
and g_socket_send_message() returning G_IO_ERROR_WOULD_BLOCK.

It is also problematic that that we're using synchronous IO in the
shared GDBus IO thread. It means that one GDBusConnection can lock up
others.

It turns out that by porting from g_output_stream_write() to
g_output_stream_write_async() we fix the EAGAIN issue. For GSocket, we
still need to handle things manually (by creating a GSource) as
g_socket_send_message() is used.

We check the new behavior in Michael's producer/consumer test case (at
/gdbus/overflow in gdbus-peer.c) added in the last commit.

Also add a test case that sends and receives a 20 MiB message.

Also add a new `transport' G_DBUS_DEBUG option so it is easy to
inspect partial writes:

 $ G_DBUS_DEBUG=transport ./gdbus-connection -p /gdbus/connection/large_message
 [...]
 ========================================================================
 GDBus-debug:Transport:
   >>>> WROTE 128000 bytes of message with serial 4 and
        size 20971669 from offset 0 on a GSocketOutputStream
 ========================================================================
 GDBus-debug:Transport:
   >>>> WROTE 128000 bytes of message with serial 4 and
        size 20971669 from offset 128000 on a GSocketOutputStream
 ========================================================================
 GDBus-debug:Transport:
   >>>> WROTE 128000 bytes of message with serial 4 and
        size 20971669 from offset 256000 on a GSocketOutputStream
 [...]
 ========================================================================
 GDBus-debug:Transport:
   >>>> WROTE 43669 bytes of message with serial 4 and
        size 20971669 from offset 20928000 on a GSocketOutputStream
 [...]
 ========================================================================
 GDBus-debug:Transport:
   <<<< READ 16 bytes of message with serial 3 and
        size 20971620 to offset 0 from a GSocketInputStream
 ========================================================================
 GDBus-debug:Transport:
   <<<< READ 15984 bytes of message with serial 3 and
        size 20971620 to offset 16 from a GSocketInputStream
 ========================================================================
 GDBus-debug:Transport:
   <<<< READ 16000 bytes of message with serial 3 and
        size 20971620 to offset 16000 from a GSocketInputStream
 [...]
 ========================================================================
 GDBus-debug:Transport:
   <<<< READ 144000 bytes of message with serial 3 and
        size 20971620 to offset 20720000 from a GSocketInputStream
 ========================================================================
 GDBus-debug:Transport:
   <<<< READ 107620 bytes of message with serial 3 and
        size 20971620 to offset 20864000 from a GSocketInputStream
 OK

https://bugzilla.gnome.org/show_bug.cgi?id=626748

Signed-off-by: David Zeuthen <davidz@redhat.com>
This commit is contained in:
David Zeuthen
2010-08-16 13:43:35 -04:00
parent a6264a3a19
commit 8a3a4596e2
5 changed files with 607 additions and 165 deletions
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4
docs/reference/gio/overview.xml
View File

@@ -339,6 +339,10 @@
cause GLib to print out different types of debugging
information when using the D-Bus routines.
<variablelist>
<varlistentry>
<term>transport</term>
<listitem><para>Show IO activity (e.g. reads and writes)</para></listitem>
</varlistentry>
<varlistentry>
<term>message</term>
<listitem><para>Show all sent and received D-Bus messages</para></listitem>