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/*
Copyright (c) 2011 - 2012, Monty Program Ab
This program is free software; you can redistribute it and/or modify
it under the terms of the GNU General Public License as published by
the Free Software Foundation; version 2 of the License.
This program is distributed in the hope that it will be useful,
but WITHOUT ANY WARRANTY; without even the implied warranty of
MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the
GNU General Public License for more details.
You should have received a copy of the GNU General Public License
along with this program; if not, write to the Free Software
Foundation, Inc., 59 Temple Place, Suite 330, Boston, MA 02111-1307 USA */
/*
Interface
~~~~~~~~~
(
- This is an APC request queue
- We assume there is a particular owner thread which periodically calls
process_apc_requests() to serve the call requests.
- Other threads can post call requests, and block until they are exectued.
)
Implementation
~~~~~~~~~~~~~~
- The target has a mutex-guarded request queue.
- After the request has been put into queue, the requestor waits for request
to be satisfied. The worker satisifes the request and signals the
requestor.
*/
/*
Target for asynchronous procedue calls (APCs).
*/
class Apc_target
{
mysql_mutex_t *LOCK_thd_data_ptr;
public:
Apc_target() : enabled(0), apc_calls(NULL) {}
~Apc_target() { DBUG_ASSERT(!enabled && !apc_calls);}
void init(mysql_mutex_t *target_mutex);
void destroy();
void enable();
void disable();
void process_apc_requests();
/* Functor class for calls you can schedule */
class Apc_call
{
public:
/* This function will be called in the target thread */
virtual void call_in_target_thread()= 0;
virtual ~Apc_call() {}
};
/* Make a call in the target thread (see function definition for details) */
bool make_apc_call(Apc_call *call, int timeout_sec, bool *timed_out);
#ifndef DBUG_OFF
int n_calls_processed; /* Number of calls served by this target */
#endif
private:
class Call_request;
/*
Non-zero value means we're enabled. It's an int, not bool, because one can
call enable() N times (and then needs to call disable() N times before the
target is really disabled)
*/
int enabled;
/*
Circular, double-linked list of all enqueued call requests.
We use this structure, because we
- process requests sequentially (i.e. they are removed from the front)
- a thread that has posted a request may time out (or be KILLed) and
cancel the request, which means we need a fast request-removal
operation.
*/
Call_request *apc_calls;
class Call_request
{
public:
Apc_call *call; /* Functor to be called */
/* The caller will actually wait for "processed==TRUE" */
bool processed;
/* Condition that will be signalled when the request has been served */
mysql_cond_t COND_request;
/* Double linked-list linkage */
Call_request *next;
Call_request *prev;
const char *what; /* (debug) state of the request */
};
void enqueue_request(Call_request *qe);
void dequeue_request(Call_request *qe);
/* return the first call request in queue, or NULL if there are none enqueued */
Call_request *get_first_in_queue()
{
return apc_calls;
}
};
///////////////////////////////////////////////////////////////////////
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