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  1. 07 Dec, 2012 8 commits
    • Paul Gortmaker's avatar
      tipc: refactor accept() code for improved readability · 0fef8f20
      Paul Gortmaker authored 
      In TIPC's accept() routine, there is a large block of code relating
to initialization of a new socket, all within an if condition checking
if the allocation succeeded.

Here, we simply flip the check of the if, so that the main execution
path stays at the same indentation level, which improves readability.
If the allocation fails, we jump to an already existing exit label.
Signed-off-by: default avatarPaul Gortmaker <paul.gortmaker@windriver.com>
      0fef8f20
    • Ying Xue's avatar
      tipc: add lock nesting notation to quiet lockdep warning · 258f8667
      Ying Xue authored 
      TIPC accept() call grabs the socket lock on a newly allocated
socket while holding the socket lock on an old socket. But lockdep
worries that this might be a recursive lock attempt:

  [ INFO: possible recursive locking detected ]
  ---------------------------------------------
  kworker/u:0/6 is trying to acquire lock:
  (sk_lock-AF_TIPC){+.+.+.}, at: [<c8c1226c>] accept+0x15c/0x310 [tipc]

  but task is already holding lock:
  (sk_lock-AF_TIPC){+.+.+.}, at: [<c8c12138>] accept+0x28/0x310 [tipc]

  other info that might help us debug this:
  Possible unsafe locking scenario:

          CPU0
          ----
          lock(sk_lock-AF_TIPC);
          lock(sk_lock-AF_TIPC);

          *** DEADLOCK ***

  May be due to missing lock nesting notation
  [...]

Tell lockdep that this locking is safe by using lock_sock_nested().
This is similar to what was done in commit 5131a184 for
SCTP code ("SCTP: lock_sock_nested in sctp_sock_migrate").

Also note that this is isn't something that is seen normally,
as it was uncovered with some experimental work-in-progress
code not yet ready for mainline.  So no need for stable
backports or similar of this commit.
Signed-off-by: default avatarYing Xue <ying.xue@windriver.com>
Signed-off-by: default avatarPaul Gortmaker <paul.gortmaker@windriver.com>
      258f8667
    • Ying Xue's avatar
      tipc: eliminate connection setup for implied connect in recv_msg() · cbab3687
      Ying Xue authored 
      As connection setup is now completed asynchronously in BH context,
in the function filter_connect(), the corresponding code in recv_msg()
becomes redundant.
Signed-off-by: default avatarYing Xue <ying.xue@windriver.com>
Signed-off-by: default avatarJon Maloy <jon.maloy@ericsson.com>
Signed-off-by: default avatarPaul Gortmaker <paul.gortmaker@windriver.com>
      cbab3687
    • Ying Xue's avatar
      tipc: introduce non-blocking socket connect · 584d24b3
      Ying Xue authored 
      TIPC has so far only supported blocking connect(), meaning that a call
to connect() doesn't return until either the connection is fully
established, or an error occurs. This has proved insufficient for many
users, so we now introduce non-blocking connect(), analogous to how
this is done in TCP and other protocols.

With this feature, if a connection cannot be established instantly,
connect() will return the error code "-EINPROGRESS".
If the user later calls connect() again, he will either have the
return code "-EALREADY" or "-EISCONN", depending on whether the
connection has been established or not.

The user must have explicitly set the socket to be non-blocking
(SOCK_NONBLOCK or O_NONBLOCK, depending on method used), so unless
for some reason they had set this already (the socket would anyway
remain blocking in current TIPC) this change should be completely
backwards compatible.

It is also now possible to call select() or poll() to wait for the
completion of a connection.

An effect of the above is that the actual completion of a connection
may now be performed asynchronously, independent of the calls from
user space. Therefore, we now execute this code in BH context, in
the function filter_rcv(), which is executed upon reception of
messages in the socket.
Signed-off-by: default avatarYing Xue <ying.xue@windriver.com>
Signed-off-by: default avatarJon Maloy <jon.maloy@ericsson.com>
[PG: minor refactoring for improved connect/disconnect function names]
Signed-off-by: default avatarPaul Gortmaker <paul.gortmaker@windriver.com>
      584d24b3
    • Ying Xue's avatar
      tipc: consolidate connection-oriented message reception in one function · 7e6c131e
      Ying Xue authored 
      Handling of connection-related message reception is currently scattered
around at different places in the code. This makes it harder to verify
that things are handled correctly in all possible scenarios.
So we consolidate the existing processing of connection-oriented
message reception in a single routine.  In the process, we convert the
chain of if/else into a switch/case for improved readability.

A cast on the socket_state in the switch is needed to avoid compile
warnings on 32 bit, like "net/tipc/socket.c:1252:2: warning: case value
‘4294967295’ not in enumerated type".  This happens because existing
tipc code pseudo extends the default linux socket state values with:

	#define SS_LISTENING    -1      /* socket is listening */
	#define SS_READY        -2      /* socket is connectionless */

It may make sense to add these as _positive_ values to the existing
socket state enum list someday, vs. these already existing defines.
Signed-off-by: default avatarYing Xue <ying.xue@windriver.com>
Signed-off-by: default avatarJon Maloy <jon.maloy@ericsson.com>
[PG: add cast to fix warning; remove returns from middle of switch]
Signed-off-by: default avatarPaul Gortmaker <paul.gortmaker@windriver.com>
      7e6c131e
    • Paul Gortmaker's avatar
      tipc: standardize across connect/disconnect function naming · bc879117
      Paul Gortmaker authored 
      Currently we have tipc_disconnect and tipc_disconnect_port.  It is
not clear from the names alone, what they do or how they differ.
It turns out that tipc_disconnect just deals with the port locking
and then calls tipc_disconnect_port which does all the work.

If we rename as follows: tipc_disconnect_port --> __tipc_disconnect
then we will be following typical linux convention, where:

   __tipc_disconnect: "raw" function that does all the work.

   tipc_disconnect: wrapper that deals with locking and then calls
		    the real core __tipc_disconnect function

With this, the difference is immediately evident, and locking
violations are more apt to be spotted by chance while working on,
or even just while reading the code.

On the connect side of things, we currently only have the single
"tipc_connect2port" function.  It does both the locking at enter/exit,
and the core of the work.  Pending changes will make it desireable to
have the connect be a two part locking wrapper + worker function,
just like the disconnect is already.

Here, we make the connect look just like the updated disconnect case,
for the above reason, and for consistency.  In the process, we also
get rid of the "2port" suffix that was on the original name, since
it adds no descriptive value.

On close examination, one might notice that the above connect
changes implicitly move the call to tipc_link_get_max_pkt() to be
within the scope of tipc_port_lock() protected region; when it was
not previously.  We don't see any issues with this, and it is in
keeping with __tipc_connect doing the work and tipc_connect just
handling the locking.
Signed-off-by: default avatarPaul Gortmaker <paul.gortmaker@windriver.com>
      bc879117
    • Jon Maloy's avatar
      tipc: change sk_receive_queue upper limit · e643df15
      Jon Maloy authored 
      The sk_recv_queue upper limit for connectionless sockets has empirically
turned out to be too low. When we double the current limit we get much
fewer rejected messages and no noticable negative side-effects.
Signed-off-by: default avatarJon Maloy <jon.maloy@ericsson.com>
Signed-off-by: default avatarPaul Gortmaker <paul.gortmaker@windriver.com>
      e643df15
    • Ying Xue's avatar
      tipc: eliminate aggregate sk_receive_queue limit · 9da3d475
      Ying Xue authored 
      As a complement to the per-socket sk_recv_queue limit, TIPC keeps a
global atomic counter for the sum of sk_recv_queue sizes across all
tipc sockets. When incremented, the counter is compared to an upper
threshold value, and if this is reached, the message is rejected
with error code TIPC_OVERLOAD.

This check was originally meant to protect the node against
buffer exhaustion and general CPU overload. However, all experience
indicates that the feature not only is redundant on Linux, but even
harmful. Users run into the limit very often, causing disturbances
for their applications, while removing it seems to have no negative
effects at all. We have also seen that overall performance is
boosted significantly when this bottleneck is removed.

Furthermore, we don't see any other network protocols maintaining
such a mechanism, something strengthening our conviction that this
control can be eliminated.

As a result, the atomic variable tipc_queue_size is now unused
and so it can be deleted.  There is a getsockopt call that used
to allow reading it; we retain that but just return zero for
maximum compatibility.
Signed-off-by: default avatarYing Xue <ying.xue@windriver.com>
Signed-off-by: default avatarJon Maloy <jon.maloy@ericsson.com>
Cc: Neil Horman <nhorman@tuxdriver.com>
[PG: phase out tipc_queue_size as pointed out by Neil Horman]
Signed-off-by: default avatarPaul Gortmaker <paul.gortmaker@windriver.com>
      9da3d475
  3. 06 Dec, 2012 2 commits
  5. 05 Dec, 2012 10 commits
  7. 04 Dec, 2012 20 commits
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