erl_bif_timer.c

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/* ``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 via the world wide web 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.
 * 
 * The Initial Developer of the Original Code is Ericsson Utvecklings AB.
 * Portions created by Ericsson are Copyright 1999, Ericsson Utvecklings
 * AB. All Rights Reserved.''
 * 
 *     $Id$
 */

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

#include "erl_bif_timer.h"
#include "global.h"
#include "bif.h"
#include "error.h"
#include "big.h"

/****************************************************************************
** BIF Timer support
****************************************************************************/

#define BTM_FLG_SL_TIMER	(((Uint32) 1) << 0)
#define BTM_FLG_CANCELED	(((Uint32) 1) << 1)
#define BTM_FLG_HEAD		(((Uint32) 1) << 2)
#define BTM_FLG_BYNAME		(((Uint32) 1) << 3)
#define BTM_FLG_WRAP		(((Uint32) 1) << 4)

struct ErtsBifTimer_ {
    struct {
	union {
	    ErtsBifTimer **head;
	    ErtsBifTimer *prev;
	} u;
	ErtsBifTimer *next;
    } tab;
    union {
	Eterm name;
	struct {
	    ErtsBifTimer *prev;
	    ErtsBifTimer *next;
	    Process *ess;
	} proc;
    } receiver;
    ErlTimer tm;
    ErlHeapFragment* bp;
    Uint32 flags;
    Eterm message;
    Uint32 ref_numbers[ERTS_REF_NUMBERS];
};

#ifdef SMALL_MEMORY
#define TIMER_HASH_VEC_SZ	3331
#define BTM_PREALC_SZ		10
#else
#define TIMER_HASH_VEC_SZ	10007
#define BTM_PREALC_SZ		100
#endif
static ErtsBifTimer **bif_timer_tab;  
static Uint no_bif_timers;


static erts_smp_rwmtx_t bif_timer_lock;

#define erts_smp_safe_btm_rwlock(P, L) \
	safe_btm_lock((P), (L), 1)
#define erts_smp_safe_btm_rlock(P, L) \
	safe_btm_lock((P), (L), 0)
#define erts_smp_btm_rwlock() \
	erts_smp_rwmtx_rwlock(&bif_timer_lock)
#define erts_smp_btm_tryrwlock() \
	erts_smp_rwmtx_tryrwlock(&bif_timer_lock)
#define erts_smp_btm_rwunlock() \
	erts_smp_rwmtx_rwunlock(&bif_timer_lock)
#define erts_smp_btm_rlock() \
	erts_smp_rwmtx_rlock(&bif_timer_lock)
#define erts_smp_btm_tryrlock() \
	erts_smp_rwmtx_tryrlock(&bif_timer_lock)
#define erts_smp_btm_runlock() \
	erts_smp_rwmtx_runlock(&bif_timer_lock)
#define erts_smp_btm_lock_init() \
	erts_smp_rwmtx_init(&bif_timer_lock, "bif_timers")


static ERTS_INLINE int
safe_btm_lock(Process *c_p, Uint32 c_p_locks, int rw_lock)
{
    ASSERT(c_p && c_p_locks);
#ifdef ERTS_SMP
    if ((rw_lock ? erts_smp_btm_tryrwlock() : erts_smp_btm_tryrlock()) != EBUSY)
	return 0;
    erts_smp_proc_unlock(c_p, c_p_locks);
    if (rw_lock)
	erts_smp_btm_rwlock();
    else
	erts_smp_btm_rlock();
    erts_smp_proc_lock(c_p, c_p_locks);
    if (ERTS_PROC_IS_EXITING(c_p)) {
	if (rw_lock)
	    erts_smp_btm_rwunlock();
	else
	    erts_smp_btm_runlock();
	return 1;
    }
#endif
    return 0;
}

ERTS_SMP_PALLOC_IMPL(btm_pre, ErtsBifTimer, BTM_PREALC_SZ)

static ERTS_INLINE int
get_index(Uint32 *ref_numbers, Uint32 len)
{
    Uint32 hash;
    /* len can potentially be larger than ERTS_REF_NUMBERS
       if it has visited another node... */
    if (len > ERTS_REF_NUMBERS)
	len = ERTS_REF_NUMBERS;

#if ERTS_REF_NUMBERS != 3
#error "ERTS_REF_NUMBERS changed. Update me..."
#endif
    switch (len) {
    case 3: if (!ref_numbers[2]) len = 2;
    case 2: if (!ref_numbers[1]) len = 1;
    default:  break;
    }

    ASSERT(1 <= len && len <= ERTS_REF_NUMBERS);

    hash = block_hash((byte *) ref_numbers, len * sizeof(Uint32), 0x08d12e65);
    return (int) (hash % ((Uint32) TIMER_HASH_VEC_SZ));
}

static Eterm
create_ref(Uint *hp, Uint32 *ref_numbers, Uint32 len)
{
    Uint32 *datap;
    int i;


    if (len > ERTS_MAX_REF_NUMBERS) {
	/* Such large refs should no be able to appear in the emulator */
	erl_exit(1, "%s:%d: Internal error\n", __FILE__, __LINE__);
    }

#ifdef ARCH_64
    hp[0] = make_ref_thing_header(len/2 + 1);
    datap = (Uint32 *) &hp[1];
    *(datap++) = len;
#else
    hp[0] = make_ref_thing_header(len);
    datap = (Uint32 *) &hp[1];
#endif

    for (i = 0; i < len; i++)
	datap[i] = ref_numbers[i];

    return make_internal_ref(hp);
}

static int
eq_non_standard_ref_numbers(Uint32 *rn1, Uint32 len1, Uint32 *rn2, Uint32 len2)
{
#ifdef ARCH_64
#define MAX_REF_HEAP_SZ (1+(ERTS_MAX_REF_NUMBERS/2+1))
#else
#define MAX_REF_HEAP_SZ (1+ERTS_MAX_REF_NUMBERS)
#endif
    Uint r1_hp[MAX_REF_HEAP_SZ];
    Uint r2_hp[MAX_REF_HEAP_SZ];

    return eq(create_ref(r1_hp, rn1, len1), create_ref(r2_hp, rn2, len2));
#undef MAX_REF_HEAP_SZ
}

static ERTS_INLINE int
eq_ref_numbers(Uint32 *rn1, Uint32 len1, Uint32 *rn2, Uint32 len2)
{
    int res;
    if (len1 != ERTS_REF_NUMBERS || len2 != ERTS_REF_NUMBERS) {
	/* Can potentially happen, but will never... */
	return eq_non_standard_ref_numbers(rn1, len1, rn2, len2);
    }

#if ERTS_REF_NUMBERS != 3
#error "ERTS_REF_NUMBERS changed. Update me..."
#endif
    res = rn1[0] == rn2[0] && rn1[1] == rn2[1] && rn1[2] == rn2[2];

    ASSERT(res
	   ? eq_non_standard_ref_numbers(rn1, len1, rn2, len2)
	   : !eq_non_standard_ref_numbers(rn1, len1, rn2, len2));

    return res;
}

static ERTS_INLINE ErtsBifTimer *
tab_find(Eterm ref)
{
    Uint32 *ref_numbers = internal_ref_numbers(ref);
    Uint32 ref_numbers_len = internal_ref_no_of_numbers(ref);
    int ix = get_index(ref_numbers, ref_numbers_len);
    ErtsBifTimer* btm;

    for (btm = bif_timer_tab[ix]; btm; btm = btm->tab.next)
	if (eq_ref_numbers(ref_numbers, ref_numbers_len,
			   btm->ref_numbers, ERTS_REF_NUMBERS))
	    return btm;
    return NULL;
}

static ERTS_INLINE void
tab_remove(ErtsBifTimer* btm)
{
    if (btm->flags & BTM_FLG_HEAD) {
	*btm->tab.u.head = btm->tab.next;
	if (btm->tab.next) {
	    btm->tab.next->flags |= BTM_FLG_HEAD;
	    btm->tab.next->tab.u.head = btm->tab.u.head;
	}
    }
    else {
	btm->tab.u.prev->tab.next = btm->tab.next;
	if (btm->tab.next)
	    btm->tab.next->tab.u.prev = btm->tab.u.prev;
    }
    btm->flags |= BTM_FLG_CANCELED;
    ASSERT(no_bif_timers > 0);
    no_bif_timers--;
}

static ERTS_INLINE void
tab_insert(ErtsBifTimer* btm)
{
    int ix = get_index(btm->ref_numbers, ERTS_REF_NUMBERS);
    ErtsBifTimer* btm_list = bif_timer_tab[ix];

    if (btm_list) {
	btm_list->flags &= ~BTM_FLG_HEAD;
	btm_list->tab.u.prev = btm;
    }

    btm->flags |= BTM_FLG_HEAD;
    btm->tab.u.head = &bif_timer_tab[ix];
    btm->tab.next = btm_list;
    bif_timer_tab[ix] = btm;
    no_bif_timers++;
}

static ERTS_INLINE void
link_proc(Process *p, ErtsBifTimer* btm)
{
    btm->receiver.proc.ess = p;
    btm->receiver.proc.prev = NULL;
    btm->receiver.proc.next = p->bif_timers;
    if (p->bif_timers)	
	p->bif_timers->receiver.proc.prev = btm;
    p->bif_timers = btm;
}

static ERTS_INLINE void
unlink_proc(ErtsBifTimer* btm)
{
    if (btm->receiver.proc.prev)
	btm->receiver.proc.prev->receiver.proc.next = btm->receiver.proc.next;
    else
	btm->receiver.proc.ess->bif_timers = btm->receiver.proc.next;
    if (btm->receiver.proc.next)
	btm->receiver.proc.next->receiver.proc.prev = btm->receiver.proc.prev;
}

static void
bif_timer_cleanup(ErtsBifTimer* btm)
{
    ASSERT(btm);

    if (btm->bp)
	free_message_buffer(btm->bp);

    ERTS_PROC_LESS_MEM(sizeof(ErtsBifTimer));
    if (!btm_pre_free(btm)) {
	if (btm->flags & BTM_FLG_SL_TIMER)
	    erts_free(ERTS_ALC_T_SL_BIF_TIMER, (void *) btm);
	else
	    erts_free(ERTS_ALC_T_LL_BIF_TIMER, (void *) btm);
    }
}

static void
bif_timer_timeout(ErtsBifTimer* btm)
{
    ASSERT(btm);


    erts_smp_btm_rwlock();

    if (btm->flags & BTM_FLG_CANCELED) {
    /*
     * A concurrent cancel is ongoing. Do not send the timeout message,
     * but cleanup here since the cancel call-back won't be called.
     */
#ifndef ERTS_SMP
	ASSERT(0);
#endif
    }
    else {
	Uint32 rp_locks = ERTS_PROC_LOCKS_MSG_SEND;
	Process* rp;

	tab_remove(btm);

	ASSERT(!erts_get_current_process());

	if (btm->flags & BTM_FLG_BYNAME)
	    rp = erts_whereis_process(NULL,0,btm->receiver.name,rp_locks,0);
	else {
	    rp = btm->receiver.proc.ess;
	    erts_smp_proc_lock(rp, rp_locks);
	    unlink_proc(btm);
	    if (ERTS_PROC_IS_EXITING(rp)) {
		erts_smp_proc_unlock(rp, rp_locks);
		rp = NULL;
	    }
	}

	if (rp) {
	    if (!ERTS_PROC_PENDING_EXIT(rp)) {
		Eterm message;
		ErlHeapFragment *bp;

		bp = btm->bp;
		btm->bp = NULL; /* Prevent cleanup of message buffer... */

		if (!(btm->flags & BTM_FLG_WRAP))
		    message = btm->message;
		else {
#if ERTS_REF_NUMBERS != 3
#error "ERTS_REF_NUMBERS changed. Update me..."
#endif
		    Eterm ref;
		    Uint *hp;
		    Uint wrap_size = REF_THING_SIZE + 4;
		    message = btm->message;

#ifndef HEAP_FRAG_ELIM_TEST
#ifdef ERTS_SMP
		    if (erts_smp_proc_trylock(rp, ERTS_PROC_LOCK_MAIN) == 0) {
			rp_locks |= ERTS_PROC_LOCK_MAIN;
#endif
			if (bp != NULL) {
			    erts_link_mbuf_to_proc(rp, bp);
			    bp = NULL;