[Barrelfish-users] Threads using sockets may block

[Chothia Zaheer]

Hello,

When multiple threads use the sockets API some calls may block indefinitely.
It seems this is because they use the default waitset -> lib/posixcompat/sockets.c:

  ssize_t recv(int sockfd, void *buf, size_t len, int flags)
                    // XXX: Assume it was on the default waitset
                    err = us->u.active.binding->change_waitset
                        (us->u.active.binding, get_default_waitset());

A simple server-client example is attached.  Output looks like this:
 
  fish> /sockets both
  spawnd.0: spawning /sockets on core 0
  LWIP: in lwip_init
  #### sockets Going ahead with default wait-set
  LWIP: done with sanity check
  idc_c_port_mng_srv: trying to [e1000_PORTS_MNG]
  idc_c_port_mng_srv: success [e1000_PORTS_MNG]
  idc_c_ARP_lookup_srv: trying to [e1000_ARP]
  idc_c_ARP_lookup_srv: success [e1000_ARP]
  LWIP: done with connection setup
  #### [0:7:sockets] [BIG] [0] MEM_SIZE[62914560], PBUF_POOL_SIZE[16384], RECEIVE_BUFFERS[2044] qid[0]####
  Created shared_pool of size(Req 131008, Actual 131072) with role [0] and slots [2044]
  Allocating 2044 pbufs
  Mapped shared_pool of size(R 131008, A 131072) with role [0], slots[2044] and pool len[2044]
  [0] new_buffer_id: buffer_id = 3
  Created shared_pool of size(Req 131008, Actual 131072) with role [1] and slots [2044]
  Mapped shared_pool of size(R 131008, A 131072) with role [1], slots[2044] and pool len[2044]
  [0] new_buffer_id: buffer_id = 4
  LWIP: getting IP from ARP service
  ####### get IP info called ######
  client: owner has the IP address 10.110.4.21
  [server] listening on port 5000.
  [client] created socket: fd = 4
  [client] connecting to server at 10.110.4.21:5000 ...
  [client] connected to server at 10.110.4.21:5000
  [client] calling read on socket
  netconn_recv called on [0x805d93d8]

The client's read call hangs and the server cannot accept or write its response.

Is there some simple approach to remedy this issue?

Regards,

--Zaheer

-------------- next part --------------
An embedded and charset-unspecified text was scrubbed...
Name: sockets_single_process.c
Url: https://lists.inf.ethz.ch/pipermail/barrelfish-users/attachments/20130211/a0c57030/attachment.c