src/slurmctld/preempt.c

/*****************************************************************************\
 *  preempt.c - Job preemption plugin function setup.
 *****************************************************************************
 *  Copyright (C) 2009 Lawrence Livermore National Security.
 *  Produced at Lawrence Livermore National Laboratory (cf, DISCLAIMER).
 *  Written by Morris Jette <jette1@llnl.gov>
 *  CODE-OCEC-09-009. All rights reserved.
 *
 *  This file is part of SLURM, a resource management program.
 *  For details, see <https://computing.llnl.gov/linux/slurm/>.
 *  Please also read the included file: DISCLAIMER.
 *
 *  SLURM 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; either version 2 of the License, or (at your option)
 *  any later version.
 *
 *  In addition, as a special exception, the copyright holders give permission
 *  to link the code of portions of this program with the OpenSSL library under
 *  certain conditions as described in each individual source file, and
 *  distribute linked combinations including the two. You must obey the GNU
 *  General Public License in all respects for all of the code used other than
 *  OpenSSL. If you modify file(s) with this exception, you may extend this
 *  exception to your version of the file(s), but you are not obligated to do
 *  so. If you do not wish to do so, delete this exception statement from your
 *  version.  If you delete this exception statement from all source files in
 *  the program, then also delete it here.
 *
 *  SLURM 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 SLURM; if not, write to the Free Software Foundation, Inc.,
 *  51 Franklin Street, Fifth Floor, Boston, MA 02110-1301  USA.
\*****************************************************************************/

#include <pthread.h>

#include "src/common/log.h"
#include "src/common/plugrack.h"
#include "src/common/slurm_protocol_api.h"
#include "src/common/xmalloc.h"
#include "src/common/xstring.h"
#include "src/slurmctld/slurmctld.h"


/* ************************************************************************ */
/*  TAG(                     slurm_preempt_ops_t                         )  */
/* ************************************************************************ */
typedef struct slurm_preempt_ops {
	List (*find_jobs)	( struct job_record *job_ptr );
} slurm_preempt_ops_t;


/* ************************************************************************ */
/*  TAG(                     slurm_preempt_contex_t                      )  */
/* ************************************************************************ */
typedef struct slurm_preempt_context {
	char	       	*preempt_type;
	plugrack_t     	plugin_list;
	plugin_handle_t	cur_plugin;
	int		preempt_errno;
	slurm_preempt_ops_t ops;
} slurm_preempt_context_t;

static slurm_preempt_context_t *g_preempt_context = NULL;
static pthread_mutex_t	    g_preempt_context_lock = PTHREAD_MUTEX_INITIALIZER;


/* ************************************************************************ */
/*  TAG(                    _slurm_preempt_get_ops                       )  */
/* ************************************************************************ */
static slurm_preempt_ops_t *
		_slurm_preempt_get_ops( slurm_preempt_context_t *c )
{
	/*
	 * Must be synchronized with slurm_preempt_ops_t above.
	 */
	static const char *syms[] = {
		"find_preemptable_jobs",
	};
	int n_syms = sizeof( syms ) / sizeof( char * );

	/* Find the correct plugin. */
        c->cur_plugin = plugin_load_and_link(c->preempt_type, n_syms, syms,
					     (void **) &c->ops);
        if ( c->cur_plugin != PLUGIN_INVALID_HANDLE )
        	return &c->ops;

	error("Couldn't find the specified plugin name for %s "
	      "looking at all files",
	      c->preempt_type);

	/* Get plugin list. */
	if ( c->plugin_list == NULL ) {
		char *plugin_dir;
		c->plugin_list = plugrack_create();
		if ( c->plugin_list == NULL ) {
			error( "cannot create plugin manager" );
			return NULL;
		}
		plugrack_set_major_type( c->plugin_list, "preempt" );
		plugrack_set_paranoia( c->plugin_list,
				       PLUGRACK_PARANOIA_NONE, 0 );
		plugin_dir = slurm_get_plugin_dir();
		plugrack_read_dir( c->plugin_list, plugin_dir );
		xfree(plugin_dir);
	}

	c->cur_plugin = plugrack_use_by_type( c->plugin_list, c->preempt_type);
	if ( c->cur_plugin == PLUGIN_INVALID_HANDLE ) {
		error( "cannot find preempt plugin for %s", c->preempt_type );
		return NULL;
	}

	/* Dereference the API. */
	if ( plugin_get_syms( c->cur_plugin,
			      n_syms,
			      syms,
			      (void **) &c->ops ) < n_syms ) {
		error( "incomplete preempt plugin detected" );
		return NULL;
	}

	return &c->ops;
}


/* ************************************************************************ */
/*  TAG(               _slurm_preempt_context_create                     )  */
/* ************************************************************************ */
static slurm_preempt_context_t *
		_slurm_preempt_context_create( const char *preempt_type )
{
	slurm_preempt_context_t *c;

	if ( preempt_type == NULL ) {
		debug3( "slurm_preempt_context:  no preempt type" );
		return NULL;
	}

	c = xmalloc( sizeof( slurm_preempt_context_t ) );
	c->preempt_type   = xstrdup( preempt_type );
	c->plugin_list    = NULL;
	c->cur_plugin     = PLUGIN_INVALID_HANDLE;
	c->preempt_errno  = SLURM_SUCCESS;

	return c;
}


/* ************************************************************************ */
/*  TAG(               _slurm_preempt_context_destroy                    )  */
/* ************************************************************************ */
static int _slurm_preempt_context_destroy( slurm_preempt_context_t *c )
{
	/*
	 * Must check return code here because plugins might still
	 * be loaded and active.
	 */
	if ( c->plugin_list ) {
		if ( plugrack_destroy( c->plugin_list ) != SLURM_SUCCESS ) {
			return SLURM_ERROR;
		}
	} else {
		plugin_unload(c->cur_plugin);
	}

	xfree( c->preempt_type );
	xfree( c );

	return SLURM_SUCCESS;
}


/* *********************************************************************** */
/*  TAG(                     slurm_preempt_init                         )  */
/* *********************************************************************** */
extern int slurm_preempt_init(void)
{
	int retval = SLURM_SUCCESS;
	char *preempt_type = NULL;

	slurm_mutex_lock( &g_preempt_context_lock );

	if ( g_preempt_context )
		goto done;

	preempt_type = slurm_get_preempt_type();
	g_preempt_context = _slurm_preempt_context_create( preempt_type );
	if ( g_preempt_context == NULL ) {
		error( "cannot create preempt context for %s",
			 preempt_type );
		retval = SLURM_ERROR;
		goto done;
	}

	if ( _slurm_preempt_get_ops( g_preempt_context ) == NULL ) {
		error( "cannot resolve preempt plugin operations" );
		_slurm_preempt_context_destroy( g_preempt_context );
		g_preempt_context = NULL;
		retval = SLURM_ERROR;
	}

 done:
	slurm_mutex_unlock( &g_preempt_context_lock );
	xfree(preempt_type);
	return retval;
}

/* *********************************************************************** */
/*  TAG(                     slurm_preempt_fini                         )  */
/* *********************************************************************** */
extern int slurm_preempt_fini(void)
{
	int rc;

	if (!g_preempt_context)
		return SLURM_SUCCESS;

	rc = _slurm_preempt_context_destroy(g_preempt_context);
	g_preempt_context = NULL;
	return rc;
}


/* *********************************************************************** */
/*  TAG(                   slurm_find_preemptable_jobs                  )  */
/* *********************************************************************** */
extern List slurm_find_preemptable_jobs(struct job_record *job_ptr)
{
	if ( slurm_preempt_init() < 0 )
		return NULL;

	return (*(g_preempt_context->ops.find_jobs))(job_ptr);
}