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fs_rom: make read-packet handling more robust

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With the introduction of the CONTENT_CHANGED notifications delivered via
the packet stream, the assumption that no more than one READ packet is
in flight at all times does no longer hold. If the fs server responds
to a CONTENT_CHANGED packet while the fs_rom expects the completion of a
read request, the '_update_dataspace' method would prematurely return,
leaving the dataspace unpopulated. This patch solves the problem by
specifically waiting for the completion of the read request.
This commit is contained in:
Norman Feske 2017-06-27 12:51:42 +02:00 committed by Christian Helmuth
parent 0b580628cf
commit bfcdab6079
1 changed files with 16 additions and 6 deletions
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22
repos/os/src/server/fs_rom/main.cc
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@ -269,6 +269,10 @@ class Fs_rom::Rom_session_component :
return;
}
/* omit read if file is empty */
if (_file_size == 0)
return;
/* read content from file */
Tx_source &source = *_fs.tx();
while (_file_seek < _file_size) {
@ -285,8 +289,14 @@ class Fs_rom::Rom_session_component :
source.submit_packet(packet);
}
/* process ack at the global signal handler */
_env.ep().wait_and_dispatch_one_io_signal();
/*
* Process the global signal handler until we got a response
* for the read request (indicated by a change of the seek
* position).
*/
size_t const orig_file_seek = _file_seek;
while (_file_seek == orig_file_seek)
_env.ep().wait_and_dispatch_one_io_signal();
}
}
@ -366,9 +376,9 @@ class Fs_rom::Rom_session_component :
return false;
if (packet.position() > _file_seek || _file_seek >= _file_size) {
error("bad packet seek position");
_file_ds.realloc(&_env.ram(), 0);
return true;
error("bad packet seek position");
_file_ds.realloc(&_env.ram(), 0);
return true;
}
size_t const n = min(packet.length(), _file_size - _file_seek);
@ -398,7 +408,7 @@ struct Fs_rom::Packet_handler : Genode::Io_signal_handler<Packet_handler>
while (source.ack_avail()) {
File_system::Packet_descriptor pack = source.get_acked_packet();
for (Rom_session_component *session = sessions.first();
session; session = session->next())
session; session = session->next())
{
if (session->process_packet(pack))
break;