Use rwlock for driver list

Conflicts:

	erts/emulator/beam/io.c

3 files changed, 84 insertions, 69 deletions

diff --git a/erts/emulator/beam/erl_bif_ddll.c b/erts/emulator/beam/erl_bif_ddll.c
index e18b1f0159..2b6deae7be 100644
--- a/erts/emulator/beam/erl_bif_ddll.c
+++ b/erts/emulator/beam/erl_bif_ddll.c
@@ -104,12 +104,18 @@ static void dereference_all_processes(DE_Handle *dh);
 static void restore_process_references(DE_Handle *dh);
 static void ddll_no_more_references(void *vdh);
 
-#define lock_drv_list() erts_smp_mtx_lock(&erts_driver_list_lock)
-#define unlock_drv_list() erts_smp_mtx_unlock(&erts_driver_list_lock)
+#define lock_drv_list() erts_smp_rwmtx_rwlock(&erts_driver_list_lock)
+#define unlock_drv_list() erts_smp_rwmtx_rwunlock(&erts_driver_list_lock)
 #define assert_drv_list_locked() \
-    ERTS_SMP_LC_ASSERT(erts_smp_lc_mtx_is_locked(&erts_driver_list_lock))
+    ERTS_SMP_LC_ASSERT(erts_smp_lc_rwmtx_is_rwlocked(&erts_driver_list_lock) \
+		       || erts_smp_lc_rwmtx_is_rlocked(&erts_driver_list_lock))
+#define assert_drv_list_rwlocked() \
+    ERTS_SMP_LC_ASSERT(erts_smp_lc_rwmtx_is_rwlocked(&erts_driver_list_lock))
+#define assert_drv_list_rlocked() \
+    ERTS_SMP_LC_ASSERT(erts_smp_lc_rwmtx_is_rlocked(&erts_driver_list_lock))
 #define assert_drv_list_not_locked() \
-    ERTS_SMP_LC_ASSERT(!erts_smp_lc_mtx_is_locked(&erts_driver_list_lock))
+    ERTS_SMP_LC_ASSERT(!erts_smp_lc_rwmtx_is_rwlocked(&erts_driver_list_lock) \
+		       && !erts_smp_lc_rwmtx_is_rlocked(&erts_driver_list_lock))
 
 
 #define FREE_PORT_FLAGS (ERTS_PORT_SFLGS_DEAD & (~ERTS_PORT_SFLG_INITIALIZING))
@@ -383,7 +389,7 @@ BIF_RETTYPE erl_ddll_try_load_3(BIF_ALIST_3)
 	    ok_term = mkatom("loaded");
 	}
     }
-    assert_drv_list_locked();
+    assert_drv_list_rwlocked();
     if (kill_ports) {
  	/* Avoid closing the driver by referencing it */
 	erts_ddll_reference_driver(dh);
@@ -582,13 +588,13 @@ Eterm erl_ddll_try_unload_2(BIF_ALIST_2)
 	dh->reload_full_path = dh->reload_driver_name = NULL; 
 	dh->reload_flags = 0;
     } 
-    if (dh->port_count > 0) {
+    if (erts_smp_atomic32_read_nob(&dh->port_count) > 0) {
 	++kill_ports;
     }
     dh->status = ERL_DE_UNLOAD;
     ok_term = am_pending_driver;
 done:
-    assert_drv_list_locked();
+    assert_drv_list_rwlocked();
     if (kill_ports > 1) {
 	/* Avoid closing the driver by referencing it */
 	erts_ddll_reference_driver(dh);
@@ -766,7 +772,7 @@ BIF_RETTYPE erl_ddll_info_2(BIF_ALIST_2)
 	} else if (drv->handle->status == ERL_DE_PERMANENT) {
 	    res = am_permanent;
 	} else {
-	    res = make_small(drv->handle->port_count);
+	    res = make_small(erts_smp_atomic32_read_nob(&drv->handle->port_count));
 	}
 	goto done;
     case am_linked_in_driver:
@@ -1024,7 +1030,8 @@ void erts_ddll_proc_dead(Process *p, ErtsProcLocks plocks)
 		} 
 		dh->status = ERL_DE_UNLOAD;
 	    }
-	    if (!left && drv->handle->port_count > 0) {
+	    if (!left
+		&& erts_smp_atomic32_read_nob(&drv->handle->port_count) > 0) {
 		if (kill_ports) {
 		    DE_Handle *dh = drv->handle;
 		    erts_ddll_reference_driver(dh);
@@ -1054,7 +1061,7 @@ void erts_ddll_proc_dead(Process *p, ErtsProcLocks plocks)
 void erts_ddll_lock_driver(DE_Handle *dh, char *name)
 {
     DE_ProcEntry *p,*q;
-    assert_drv_list_locked();
+    assert_drv_list_rwlocked();
     notify_all(dh, name, 
 	       ERL_DE_PROC_AWAIT_LOAD, am_UP, am_permanent);
     notify_all(dh, name, 
@@ -1077,19 +1084,22 @@ void erts_ddll_lock_driver(DE_Handle *dh, char *name)
 void erts_ddll_increment_port_count(DE_Handle *dh) 
 {
     assert_drv_list_locked();
-    dh->port_count++;
+    erts_smp_atomic32_inc_nob(&dh->port_count);
 }
 
 void erts_ddll_decrement_port_count(DE_Handle *dh)
 {
     assert_drv_list_locked();
-    ASSERT(dh->port_count > 0);
-    dh->port_count--;
+#if DEBUG
+    ASSERT(erts_smp_atomic32_dec_read_nob(&dh->port_count) >= 0);
+#else
+    erts_smp_atomic32_dec_nob(&dh->port_count);
+#endif
 }
 
 static void first_ddll_reference(DE_Handle *dh) 
 {
-    assert_drv_list_locked();
+    assert_drv_list_rwlocked();
     erts_refc_init(&(dh->refc),1);
 }
 
@@ -1117,7 +1127,7 @@ void erts_ddll_dereference_driver(DE_Handle *dh)
 static void dereference_all_processes(DE_Handle *dh) 
 {
     DE_ProcEntry *p;
-    assert_drv_list_locked();
+    assert_drv_list_rwlocked();
     for(p  = dh->procs;p != NULL; p = p->next) {
 	if (p->awaiting_status == ERL_DE_PROC_LOADED) {
 	    ASSERT(!(p->flags & ERL_DE_FL_DEREFERENCED));
@@ -1130,7 +1140,7 @@ static void dereference_all_processes(DE_Handle *dh)
 static void restore_process_references(DE_Handle *dh) 
 {
     DE_ProcEntry *p;
-    assert_drv_list_locked();
+    assert_drv_list_rwlocked();
     ASSERT(erts_refc_read(&(dh->refc),0) == 0);
     for(p  = dh->procs;p != NULL; p = p->next) {
 	if (p->awaiting_status == ERL_DE_PROC_LOADED) {
@@ -1358,7 +1368,7 @@ static int is_last_user(DE_Handle *dh, Process *proc) {
     DE_ProcEntry *p = dh->procs;
     int found = 0;
 
-    assert_drv_list_locked();
+    assert_drv_list_rwlocked();
 
     while (p != NULL) {
 	if (p->proc == proc && p->awaiting_status == ERL_DE_PROC_LOADED) {
@@ -1379,7 +1389,7 @@ static DE_ProcEntry *find_proc_entry(DE_Handle *dh, Process *proc, Uint status)
 {
     DE_ProcEntry *p = dh->procs;
 
-    assert_drv_list_locked();
+    assert_drv_list_rwlocked();
 
     while (p != NULL) {
 	if (p->proc == proc && p->awaiting_status == status) {
@@ -1406,7 +1416,7 @@ static int num_procs(DE_Handle *dh, Uint status) {
     DE_ProcEntry *p = dh->procs;
     int i = 0;
 
-    assert_drv_list_locked();
+    assert_drv_list_rwlocked();
 
     while (p != NULL) {
 	if (p->awaiting_status == status) {
@@ -1421,7 +1431,7 @@ static int num_entries(DE_Handle *dh, Process *proc, Uint status) {
     DE_ProcEntry *p = dh->procs;
     int i = 0;
 
-    assert_drv_list_locked();
+    assert_drv_list_rwlocked();
     while (p != NULL) {
 	if (p->awaiting_status == status && p->proc == proc) {
 	    ++i;
@@ -1434,7 +1444,7 @@ static int num_entries(DE_Handle *dh, Process *proc, Uint status) {
 static void add_proc_loaded(DE_Handle *dh, Process *proc) 
 {
     DE_ProcEntry *p;
-    assert_drv_list_locked();
+    assert_drv_list_rwlocked();
     p = erts_alloc(ERTS_ALC_T_DDLL_PROCESS, sizeof(DE_ProcEntry));
     p->proc = proc;
     p->flags = 0;
@@ -1446,7 +1456,7 @@ static void add_proc_loaded(DE_Handle *dh, Process *proc)
 static void add_proc_loaded_deref(DE_Handle *dh, Process *proc) 
 {
     DE_ProcEntry *p;
-    assert_drv_list_locked();
+    assert_drv_list_rwlocked();
     p = erts_alloc(ERTS_ALC_T_DDLL_PROCESS, sizeof(DE_ProcEntry));
     p->proc = proc;
     p->awaiting_status = ERL_DE_PROC_LOADED;
@@ -1466,7 +1476,7 @@ static void add_proc_waiting(DE_Handle *dh, Process *proc,
 			     Uint status, Eterm ref) 
 {
     DE_ProcEntry *p;
-    assert_drv_list_locked();
+    assert_drv_list_rwlocked();
     p = erts_alloc(ERTS_ALC_T_DDLL_PROCESS, sizeof(DE_ProcEntry));
     p->proc = proc;
     p->flags = 0;
@@ -1480,7 +1490,7 @@ static Eterm add_monitor(Process *p, DE_Handle *dh, Uint status)
 {
     Eterm r;
 
-    assert_drv_list_locked();
+    assert_drv_list_rwlocked();
     r = erts_make_ref(p);
     add_proc_waiting(dh, p, status, r);
     return r;
@@ -1491,7 +1501,7 @@ static void set_driver_reloading(DE_Handle *dh, Process *proc, char *path, char
 {
     DE_ProcEntry *p;
 
-    assert_drv_list_locked();
+    assert_drv_list_rwlocked();
     p = erts_alloc(ERTS_ALC_T_DDLL_PROCESS, sizeof(DE_ProcEntry));
     p->proc = proc;
     p->awaiting_status = ERL_DE_OK;
@@ -1512,7 +1522,7 @@ static int do_load_driver_entry(DE_Handle *dh, char *path, char *name)
     int res;
     ErlDrvEntry *dp;
 
-    assert_drv_list_locked();
+    assert_drv_list_rwlocked();
 
     if ((res =  erts_sys_ddll_open(path, &(dh->handle))) != ERL_DE_NO_ERROR) {
 	return res;
@@ -1550,7 +1560,7 @@ static int do_load_driver_entry(DE_Handle *dh, char *path, char *name)
 	goto error;
     }
     erts_smp_atomic_init_nob(&(dh->refc), (erts_aint_t) 0);
-    dh->port_count = 0;
+    erts_smp_atomic32_init_nob(&dh->port_count, 0);
     dh->full_path = erts_alloc(ERTS_ALC_T_DDLL_HANDLE, sys_strlen(path) + 1);
     sys_strcpy(dh->full_path, path);
     dh->flags = 0;
@@ -1576,7 +1586,7 @@ static int do_unload_driver_entry(DE_Handle *dh, Eterm *save_name)
 {
     erts_driver_t *q, *p = driver_list;
 
-    assert_drv_list_locked();
+    assert_drv_list_rwlocked();
 
     while (p != NULL) {
 	if (p->handle == dh) {
@@ -1616,11 +1626,11 @@ static int load_driver_entry(DE_Handle **dhp, char *path, char *name)
     int res;
     DE_Handle *dh = erts_alloc(ERTS_ALC_T_DDLL_HANDLE, sizeof(DE_Handle));
 
-    assert_drv_list_locked();
+    assert_drv_list_rwlocked();
 
     dh->handle = NULL;
     dh->procs = NULL;
-    dh->port_count = 0;
+    erts_smp_atomic32_init_nob(&dh->port_count, 0);
     erts_refc_init(&(dh->refc), (erts_aint_t) 0);
     dh->status = -1;
     dh->reload_full_path = NULL;
@@ -1654,7 +1664,7 @@ static int reload_driver_entry(DE_Handle *dh)
     int loadres;
     Uint flags = dh->reload_flags;
 
-    assert_drv_list_locked();
+    assert_drv_list_rwlocked();
 
     dh->reload_full_path = NULL;
     dh->reload_driver_name = NULL;
@@ -1692,7 +1702,7 @@ static void notify_proc(Process *proc, Eterm ref, Eterm driver_name, Eterm type,
     ErtsProcLocks rp_locks = 0;
     ERTS_SMP_CHK_NO_PROC_LOCKS;
 
-    assert_drv_list_locked();
+    assert_drv_list_rwlocked();
     if (errcode != 0) {
 	int need = load_error_need(errcode);
 	Eterm e;
@@ -1725,7 +1735,7 @@ static void notify_all(DE_Handle *dh, char *name, Uint awaiting, Eterm type, Ete
 {
     DE_ProcEntry **p;
 
-    assert_drv_list_locked();
+    assert_drv_list_rwlocked();
 
     p = &(dh->procs);
     while (*p != NULL) {
@@ -1868,7 +1878,7 @@ static int build_proc_info(DE_Handle *dh, ProcEntryInfo **out_pei, Uint filter)
     int i;
     DE_ProcEntry *pe;
 
-    assert_drv_list_locked();
+    assert_drv_list_rwlocked();
 
     for (pe = dh->procs; pe != NULL; pe = pe->next) {
 	Eterm id = pe->proc->common.id;
diff --git a/erts/emulator/beam/global.h b/erts/emulator/beam/global.h
index 0de11afee9..bce4619645 100644
--- a/erts/emulator/beam/global.h
+++ b/erts/emulator/beam/global.h
@@ -110,7 +110,7 @@ typedef struct {
 				         or that wait for it to change state */
     erts_refc_t  refc;                /* Number of ports/processes having
 					 references to the driver */
-    Uint         port_count;          /* Number of ports using the driver */
+    erts_smp_atomic32_t port_count;   /* Number of ports using the driver */
     Uint         flags;               /* ERL_DE_FL_KILL_PORTS */
     int          status;              /* ERL_DE_xxx */
     char         *full_path;          /* Full path of the driver */
@@ -162,7 +162,7 @@ struct erts_driver_t_ {
 };
 
 extern erts_driver_t *driver_list;
-extern erts_smp_mtx_t erts_driver_list_lock;
+extern erts_smp_rwmtx_t erts_driver_list_lock;
 
 extern void erts_ddll_init(void);
 extern void erts_ddll_lock_driver(DE_Handle *dh, char *name);
diff --git a/erts/emulator/beam/io.c b/erts/emulator/beam/io.c
index 78c27b1385..9d38e5539e 100644
--- a/erts/emulator/beam/io.c
+++ b/erts/emulator/beam/io.c
@@ -51,7 +51,7 @@ extern ErlDrvEntry spawn_driver_entry;
 extern ErlDrvEntry *driver_tab[]; /* table of static drivers, only used during initialization */
 
 erts_driver_t *driver_list; /* List of all drivers, static and dynamic. */
-erts_smp_mtx_t erts_driver_list_lock; /* Mutex for driver list */
+erts_smp_rwmtx_t erts_driver_list_lock; /* Mutex for driver list */
 static erts_smp_tsd_key_t driver_list_lock_status_key; /*stop recursive locks when calling 
 							 driver init */
 static erts_smp_tsd_key_t driver_list_last_error_key;  /* Save last DDLL error on a 
@@ -532,14 +532,14 @@ erts_open_driver(erts_driver_t* driver,	/* Pointer to driver. */
 
     ERTS_SMP_CHK_NO_PROC_LOCKS;
 
-    erts_smp_mtx_lock(&erts_driver_list_lock);
+    erts_smp_rwmtx_rlock(&erts_driver_list_lock);
     if (!driver) {
 	for (driver = driver_list; driver; driver = driver->next) {
 	    if (sys_strcmp(driver->name, name) == 0)
 		break;
 	}
 	if (!driver) { 
-	    erts_smp_mtx_unlock(&erts_driver_list_lock);
+	    erts_smp_rwmtx_runlock(&erts_driver_list_lock);
 	    ERTS_OPEN_DRIVER_RET(NULL, -3, BADARG);
 	}
     }
@@ -584,7 +584,7 @@ erts_open_driver(erts_driver_t* driver,	/* Pointer to driver. */
     }
 
     if (driver == NULL || (driver != &spawn_driver && opts->exit_status)) {
-	erts_smp_mtx_unlock(&erts_driver_list_lock);
+	erts_smp_rwmtx_runlock(&erts_driver_list_lock);
 	ERTS_OPEN_DRIVER_RET(NULL, -3, BADARG);
     }
 
@@ -596,7 +596,7 @@ erts_open_driver(erts_driver_t* driver,	/* Pointer to driver. */
 	erts_ddll_increment_port_count(driver->handle);
 	erts_ddll_reference_driver(driver->handle);
     }
-    erts_smp_mtx_unlock(&erts_driver_list_lock);
+    erts_smp_rwmtx_runlock(&erts_driver_list_lock);
 
     /*
      * We'll set up the port before calling the start function,
@@ -606,9 +606,9 @@ erts_open_driver(erts_driver_t* driver,	/* Pointer to driver. */
     port = create_port(name, driver, driver_lock, pid, &port_errno);
     if (!port) {
 	if (driver->handle) {
-	    erts_smp_mtx_lock(&erts_driver_list_lock);
+	    erts_smp_rwmtx_rlock(&erts_driver_list_lock);
 	    erts_ddll_decrement_port_count(driver->handle);
-	    erts_smp_mtx_unlock(&erts_driver_list_lock);
+	    erts_smp_rwmtx_runlock(&erts_driver_list_lock);
 	    erts_ddll_dereference_driver(driver->handle);
 	}
 	if (port_errno)
@@ -681,9 +681,9 @@ erts_open_driver(erts_driver_t* driver,	/* Pointer to driver. */
 	    port->linebuf = NULL;
 	}
 	if (driver->handle != NULL) {
-	    erts_smp_mtx_lock(&erts_driver_list_lock);
+	    erts_smp_rwmtx_rlock(&erts_driver_list_lock);
 	    erts_ddll_decrement_port_count(driver->handle);
-	    erts_smp_mtx_unlock(&erts_driver_list_lock);
+	    erts_smp_rwmtx_runlock(&erts_driver_list_lock);
 	}
 	kill_port(port);
 	erts_port_release(port);
@@ -740,9 +740,9 @@ driver_create_port(ErlDrvPort creator_port_ix, /* Creating port */
     ERTS_SMP_LC_ASSERT(erts_lc_is_port_locked(creator_port));
 
     driver = creator_port->drv_ptr;
-    erts_smp_mtx_lock(&erts_driver_list_lock);
+    erts_smp_rwmtx_rlock(&erts_driver_list_lock);
     if (!erts_ddll_driver_ok(driver->handle)) {
-	erts_smp_mtx_unlock(&erts_driver_list_lock);
+	erts_smp_rwmtx_runlock(&erts_driver_list_lock);
 	return ERTS_INVALID_ERL_DRV_PORT;
     }
 
@@ -755,14 +755,14 @@ driver_create_port(ErlDrvPort creator_port_ix, /* Creating port */
     driver_lock = driver->lock;
 #endif
 
-    erts_smp_mtx_unlock(&erts_driver_list_lock);
+    erts_smp_rwmtx_runlock(&erts_driver_list_lock);
 
     port = create_port(name, driver, driver_lock, pid, NULL);
     if (!port) {
 	if (driver->handle) {
-	    erts_smp_mtx_lock(&erts_driver_list_lock);
+	    erts_smp_rwmtx_rlock(&erts_driver_list_lock);
 	    erts_ddll_decrement_port_count(driver->handle);
-	    erts_smp_mtx_unlock(&erts_driver_list_lock);
+	    erts_smp_rwmtx_runlock(&erts_driver_list_lock);
 	    erts_ddll_dereference_driver(driver->handle);
 	}
 	return ERTS_INVALID_ERL_DRV_PORT;
@@ -773,9 +773,9 @@ driver_create_port(ErlDrvPort creator_port_ix, /* Creating port */
     if (ERTS_PROC_IS_EXITING(rp)) {
 	erts_smp_proc_unlock(rp, ERTS_PROC_LOCK_LINK);
 	if (driver->handle) {
-	    erts_smp_mtx_lock(&erts_driver_list_lock);
+	    erts_smp_rwmtx_rlock(&erts_driver_list_lock);
 	    erts_ddll_decrement_port_count(driver->handle);
-	    erts_smp_mtx_unlock(&erts_driver_list_lock);
+	    erts_smp_rwmtx_runlock(&erts_driver_list_lock);
 	}
 	kill_port(port);
 	erts_port_release(port);
@@ -1285,6 +1285,9 @@ void erts_init_io(int port_tab_size,
 		  int port_tab_size_ignore_files)
 {
     ErlDrvEntry** dp;
+    erts_smp_rwmtx_opt_t drv_list_rwmtx_opts = ERTS_SMP_RWMTX_OPT_DEFAULT_INITER;
+    drv_list_rwmtx_opts.type = ERTS_SMP_RWMTX_TYPE_EXTREMELY_FREQUENT_READ;
+    drv_list_rwmtx_opts.lived = ERTS_SMP_RWMTX_LONG_LIVED;
 
 #ifdef ERTS_SMP
     init_xports_list_alloc();
@@ -1303,7 +1306,9 @@ void erts_init_io(int port_tab_size,
     else if (port_tab_size < ERTS_MIN_PORTS)
 	port_tab_size = ERTS_MIN_PORTS;
 
-    erts_smp_mtx_init(&erts_driver_list_lock,"driver_list");
+    erts_smp_rwmtx_init_opt(&erts_driver_list_lock,
+			    &drv_list_rwmtx_opts,
+			    "driver_list");
     driver_list = NULL;
     erts_smp_tsd_key_create(&driver_list_lock_status_key);
     erts_smp_tsd_key_create(&driver_list_last_error_key);
@@ -1321,7 +1326,7 @@ void erts_init_io(int port_tab_size,
     sys_init_io();
 
     erts_smp_tsd_set(driver_list_lock_status_key, (void *) 1);
-    erts_smp_mtx_lock(&erts_driver_list_lock);
+    erts_smp_rwmtx_rwlock(&erts_driver_list_lock);
 
     init_driver(&fd_driver, &fd_driver_entry, NULL);
     init_driver(&vanilla_driver, &vanilla_driver_entry, NULL);
@@ -1330,7 +1335,7 @@ void erts_init_io(int port_tab_size,
 	erts_add_driver_entry(*dp, NULL, 1);
 
     erts_smp_tsd_set(driver_list_lock_status_key, NULL);
-    erts_smp_mtx_unlock(&erts_driver_list_lock);
+    erts_smp_rwmtx_rwunlock(&erts_driver_list_lock);
 }
 
 /*
@@ -1921,9 +1926,9 @@ terminate_port(Port *prt)
 #endif
     }
     if(drv->handle != NULL) {
-	erts_smp_mtx_lock(&erts_driver_list_lock);
+	erts_smp_rwmtx_rlock(&erts_driver_list_lock);
 	erts_ddll_decrement_port_count(drv->handle); 
-	erts_smp_mtx_unlock(&erts_driver_list_lock);
+	erts_smp_rwmtx_runlock(&erts_driver_list_lock);
     }
     stopq(prt);        /* clear queue memory */
     if(prt->linebuf != NULL){
@@ -4725,20 +4730,20 @@ int driver_lock_driver(ErlDrvPort ix)
 
     ERTS_SMP_CHK_NO_PROC_LOCKS;
 
-    erts_smp_mtx_lock(&erts_driver_list_lock);
+    erts_smp_rwmtx_rwlock(&erts_driver_list_lock);
 
     if (prt == NULL) {
-	erts_smp_mtx_unlock(&erts_driver_list_lock);
+	erts_smp_rwmtx_rwunlock(&erts_driver_list_lock);
 	return -1;
     }
 
     ERTS_SMP_LC_ASSERT(erts_lc_is_port_locked(prt));
     if ((dh = (DE_Handle*)prt->drv_ptr->handle ) == NULL) {
-	erts_smp_mtx_unlock(&erts_driver_list_lock);
+	erts_smp_rwmtx_rwunlock(&erts_driver_list_lock);
 	return -1;
     }
     erts_ddll_lock_driver(dh, prt->drv_ptr->name);
-    erts_smp_mtx_unlock(&erts_driver_list_lock);
+    erts_smp_rwmtx_rwunlock(&erts_driver_list_lock);
     return 0;
 }
 
@@ -4748,7 +4753,7 @@ static int maybe_lock_driver_list(void)
     void *rec_lock;
     rec_lock = erts_smp_tsd_get(driver_list_lock_status_key);
     if (rec_lock == 0) {
-	erts_smp_mtx_lock(&erts_driver_list_lock);
+	erts_smp_rwmtx_rwlock(&erts_driver_list_lock);
 	return 1;
     }
     return 0;
@@ -4756,7 +4761,7 @@ static int maybe_lock_driver_list(void)
 static void maybe_unlock_driver_list(int doit)
 {
     if (doit) {
-	erts_smp_mtx_unlock(&erts_driver_list_lock);
+	erts_smp_rwmtx_rwunlock(&erts_driver_list_lock);
     }
 }
 /* 
@@ -5055,7 +5060,7 @@ int erts_add_driver_entry(ErlDrvEntry *de, DE_Handle *handle, int driver_list_lo
     int res;
 
     if (!driver_list_locked) {
-	erts_smp_mtx_lock(&erts_driver_list_lock);
+	erts_smp_rwmtx_rwlock(&erts_driver_list_lock);
     }
 
     dp->next = driver_list;
@@ -5084,7 +5089,7 @@ int erts_add_driver_entry(ErlDrvEntry *de, DE_Handle *handle, int driver_list_lo
 	
     if (!driver_list_locked) {
 	erts_smp_tsd_set(driver_list_lock_status_key, NULL);
-	erts_smp_mtx_unlock(&erts_driver_list_lock);
+	erts_smp_rwmtx_rwunlock(&erts_driver_list_lock);
     }
     return res;
 }
@@ -5097,7 +5102,7 @@ int remove_driver_entry(ErlDrvEntry *drv)
     
     rec_lock = erts_smp_tsd_get(driver_list_lock_status_key);
     if (rec_lock == NULL) {
-	erts_smp_mtx_lock(&erts_driver_list_lock);
+	erts_smp_rwmtx_rwlock(&erts_driver_list_lock);
     }
     dp = driver_list;
     while (dp && dp->entry != drv)
@@ -5105,7 +5110,7 @@ int remove_driver_entry(ErlDrvEntry *drv)
     if (dp) {
 	if (dp->handle) {
 	    if (rec_lock == NULL) {
-		erts_smp_mtx_unlock(&erts_driver_list_lock);
+		erts_smp_rwmtx_rwunlock(&erts_driver_list_lock);
 	    }
 	    return -1;
 	}
@@ -5119,12 +5124,12 @@ int remove_driver_entry(ErlDrvEntry *drv)
 	}
 	erts_destroy_driver(dp);
 	if (rec_lock == NULL) {
-	    erts_smp_mtx_unlock(&erts_driver_list_lock);
+	    erts_smp_rwmtx_rwunlock(&erts_driver_list_lock);
 	}
 	return 1;
     }
     if (rec_lock == NULL) {
-	erts_smp_mtx_unlock(&erts_driver_list_lock);
+	erts_smp_rwmtx_rwunlock(&erts_driver_list_lock);
     }
     return 0;
 }