path: root/erts/emulator/beam/code_ix.c

/*
 * %CopyrightBegin%
 *
 * Copyright Ericsson AB 2012. All Rights Reserved.
 *
 * The contents of this file are subject to the Erlang Public License,
 * Version 1.1, (the "License"); you may not use this file except in
 * compliance with the License. You should have received a copy of the
 * Erlang Public License along with this software. If not, it can be
 * retrieved online at http://www.erlang.org/.
 *
 * Software distributed under the License is distributed on an "AS IS"
 * basis, WITHOUT WARRANTY OF ANY KIND, either express or implied. See
 * the License for the specific language governing rights and limitations
 * under the License.
 *
 * %CopyrightEnd%
 */

#ifdef HAVE_CONFIG_H
#  include "config.h"
#endif

#include "code_ix.h"
#include "global.h"
#include "beam_catches.h"



#if 0
# define CIX_TRACE(text) erts_fprintf(stderr, "CIX_TRACE: " text " act=%u load=%u\r\n", erts_active_code_ix(), erts_staging_code_ix())
#else
# define CIX_TRACE(text)
#endif

erts_smp_atomic32_t the_active_code_index;
erts_smp_atomic32_t the_staging_code_index;

static int is_code_write_locked = 0;
struct code_write_queue_item {
    Process *p;
    struct code_write_queue_item* next;
};
static struct code_write_queue_item* code_write_queue = NULL;
static erts_smp_mtx_t code_write_permission_mtx;

#ifdef ERTS_ENABLE_LOCK_CHECK
static erts_tsd_key_t has_code_write_permission;
#endif

void erts_code_ix_init(void)
{
    /* We start emulator by initializing preloaded modules
     * single threaded with active and staging set both to zero.
     * Preloading is finished by a commit that will set things straight.
     */
    erts_smp_atomic32_init_nob(&the_active_code_index, 0);
    erts_smp_atomic32_init_nob(&the_staging_code_index, 0);
    erts_smp_mtx_init(&code_write_permission_mtx, "code_write_permission");
#ifdef ERTS_ENABLE_LOCK_CHECK
    erts_tsd_key_create(&has_code_write_permission);
#endif
    CIX_TRACE("init");
}

void erts_start_staging_code_ix(void)
{
    beam_catches_start_staging();
    export_start_staging();
    module_start_staging();
    erts_start_staging_ranges();
    CIX_TRACE("start");
}


void erts_end_staging_code_ix(void)
{
    beam_catches_end_staging(1);
    export_end_staging(1);
    module_end_staging(1);
    erts_end_staging_ranges(1);
    CIX_TRACE("end");
}

void erts_commit_staging_code_ix(void)
{
    ErtsCodeIndex ix;
    /* We need to this lock as we are now making the staging export table active */
    export_staging_lock();
    ix = erts_staging_code_ix();
    erts_smp_atomic32_set_nob(&the_active_code_index, ix);
    ix = (ix + 1) % ERTS_NUM_CODE_IX;
    erts_smp_atomic32_set_nob(&the_staging_code_index, ix);
    export_staging_unlock();
    CIX_TRACE("activate");
}

void erts_abort_staging_code_ix(void)
{
    beam_catches_end_staging(0);
    export_end_staging(0);
    module_end_staging(0);
    erts_end_staging_ranges(0);
    CIX_TRACE("abort");
}


/*
 * Calller _must_ yield if we return 0
 */
int erts_try_seize_code_write_permission(Process* c_p)
{
    int success;
#ifdef ERTS_SMP
    ASSERT(!erts_smp_thr_progress_is_blocking()); /* to avoid deadlock */
#endif

    erts_smp_mtx_lock(&code_write_permission_mtx);
    success = !is_code_write_locked;
    if (success) {
	is_code_write_locked = 1;
#ifdef ERTS_ENABLE_LOCK_CHECK
	erts_tsd_set(has_code_write_permission, (void *) 1);
#endif
    }
    else { /* Already locked */
	struct code_write_queue_item* qitem;
	ERTS_SMP_LC_ASSERT(!erts_tsd_get(has_code_write_permission));
	qitem = erts_alloc(ERTS_ALC_T_CODE_IX_LOCK_Q, sizeof(*qitem));
	qitem->p = c_p;
	erts_smp_proc_inc_refc(c_p);
	qitem->next = code_write_queue;
	code_write_queue = qitem;
	erts_suspend(c_p, ERTS_PROC_LOCK_MAIN, NULL);
    }
   erts_smp_mtx_unlock(&code_write_permission_mtx);
   return success;
}

void erts_release_code_write_permission(void)
{
    erts_smp_mtx_lock(&code_write_permission_mtx);
    ERTS_SMP_LC_ASSERT(erts_has_code_write_permission());
    while (code_write_queue != NULL) { /* unleash the entire herd */
	struct code_write_queue_item* qitem = code_write_queue;
	erts_smp_proc_lock(qitem->p, ERTS_PROC_LOCK_STATUS);
	if (!ERTS_PROC_IS_EXITING(qitem->p)) {
	    erts_resume(qitem->p, ERTS_PROC_LOCK_STATUS);
	}
	erts_smp_proc_unlock(qitem->p, ERTS_PROC_LOCK_STATUS);
	code_write_queue = qitem->next;
	erts_smp_proc_dec_refc(qitem->p);
	erts_free(ERTS_ALC_T_CODE_IX_LOCK_Q, qitem);
    }
    is_code_write_locked = 0;
#ifdef ERTS_ENABLE_LOCK_CHECK
    erts_tsd_set(has_code_write_permission, (void *) 0);
#endif
    erts_smp_mtx_unlock(&code_write_permission_mtx);
}

#ifdef ERTS_ENABLE_LOCK_CHECK
int erts_has_code_write_permission(void)
{
    return is_code_write_locked && erts_tsd_get(has_code_write_permission);
}
#endif