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CLEANUP: connection: fix comments in connection.h to reflect new behaviour.

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The polling has substantially changed, better fix the comments.
This commit is contained in:
Willy Tarreau 2014-01-23 15:26:18 +01:00
parent aad69387ac
commit baf5b9b445
1 changed files with 11 additions and 28 deletions
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39
include/types/connection.h
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@ -2,7 +2,7 @@
* include/types/connection.h
* This file describes the connection struct and associated constants.
*
* Copyright (C) 2000-2012 Willy Tarreau - w@1wt.eu
* Copyright (C) 2000-2014 Willy Tarreau - w@1wt.eu
*
* This library is free software; you can redistribute it and/or
* modify it under the terms of the GNU Lesser General Public
@ -37,34 +37,17 @@ struct connection;
struct buffer;
struct pipe;
/* Polling flags that are manipulated by I/O callbacks and handshake callbacks
* indicate what they expect from a file descriptor at each layer. For each
* direction, we have 2 bits, one stating whether any suspected activity on the
* FD induce a call to the iocb, and another one indicating that the FD has
* already returned EAGAIN and that polling on it is essential before calling
* the iocb again :
* POL ENA state
* 0 0 STOPPED : any activity on this FD is ignored
* 0 1 ENABLED : any (suspected) activity may call the iocb
* 1 0 STOPPED : as above
* 1 1 POLLED : the FD is being polled for activity
/* For each direction, we have a CO_FL_{SOCK,DATA}_<DIR>_ENA flag, which
* indicates if read or write is desired in that direction for the respective
* layers. The current status corresponding to the current layer being used is
* remembered in the CO_FL_CURR_<DIR>_ENA flag. The need to poll (ie receipt of
* EAGAIN) is remembered at the file descriptor level so that even when the
* activity is stopped and restarted, we still remember whether it was needed
* to poll before attempting the I/O.
*
* - Enabling an I/O event consists in ORing with 1.
* - Stopping an I/O event consists in ANDing with ~1.
* - Polling for an I/O event consists in ORing with ~3.
*
* The last ENA state is remembered in CO_FL_CURR_* so that differential
* changes can be applied. After bits are applied, the POLL status bits are
* cleared so that it is possible to detect when an EAGAIN was encountered. For
* pollers that do not support speculative I/O, POLLED is the same as ENABLED
* and the POL flag can safely be ignored. However it makes a difference for
* the connection handler.
*
* The ENA flags are per-layer (one pair for SOCK, another one for DATA). The
* POL flags are irrelevant to these layers and only reflect the fact that
* EAGAIN was encountered, they're materialised by the CO_FL_WAIT_* connection
* flags. POL flags always indicate a polling change because it is assumed that
* the poller uses a cache and does not always poll.
* The CO_FL_CURR_<DIR>_ENA flag is set from the FD status in
* conn_refresh_polling_flags(). The FD state is updated according to these
* flags in conn_cond_update_polling().
*/
/* flags for use in connection->flags */