Make it possible to reread and update detected CPU information

Calling erlang:system_info/1 with the new argument 'update_cpu_info'
will make the runtime system reread and update the internally stored
CPU information. For more information see the documentation of
erlang:system_info(update_cpu_info).

3 files changed, 56 insertions, 4 deletions

diff --git a/erts/emulator/beam/erl_bif_info.c b/erts/emulator/beam/erl_bif_info.c
index 5128776c47..d5ae3d2174 100644
--- a/erts/emulator/beam/erl_bif_info.c
+++ b/erts/emulator/beam/erl_bif_info.c
@@ -2316,6 +2316,15 @@ BIF_RETTYPE system_info_1(BIF_ALIST_1)
     } else if (ERTS_IS_ATOM_STR("cpu_topology", BIF_ARG_1)) {
 	res = erts_get_cpu_topology_term(BIF_P, am_used);
 	BIF_TRAP1(erts_format_cpu_topology_trap, BIF_P, res);
+    } else if (ERTS_IS_ATOM_STR("update_cpu_info", BIF_ARG_1)) {
+	if (erts_update_cpu_info()) {
+	    ERTS_DECL_AM(changed);
+	    BIF_RET(AM_changed);
+	}
+	else {
+	    ERTS_DECL_AM(unchanged);
+	    BIF_RET(AM_unchanged);
+	}
 #if defined(__GNUC__) && defined(HAVE_SOLARIS_SPARC_PERFMON)
     } else if (ERTS_IS_ATOM_STR("ultrasparc_read_tick1", BIF_ARG_1)) {
 	register unsigned high asm("%l0");
@@ -2387,7 +2396,10 @@ BIF_RETTYPE system_info_1(BIF_ALIST_1)
     }
     /* Arguments that are unusual follow ... */
     else if (ERTS_IS_ATOM_STR("logical_processors", BIF_ARG_1)) {
-	int no = erts_get_cpu_configured(erts_cpuinfo);
+	int no;
+	erts_smp_rwmtx_rlock(&erts_cpu_bind_rwmtx);
+	no = erts_get_cpu_configured(erts_cpuinfo);
+	erts_smp_rwmtx_runlock(&erts_cpu_bind_rwmtx);
 	if (no > 0)
 	    BIF_RET(make_small((Uint) no));
 	else {
@@ -2396,7 +2408,10 @@ BIF_RETTYPE system_info_1(BIF_ALIST_1)
 	}
     }
     else if (ERTS_IS_ATOM_STR("logical_processors_online", BIF_ARG_1)) {
-	int no = erts_get_cpu_online(erts_cpuinfo);
+	int no;
+	erts_smp_rwmtx_rlock(&erts_cpu_bind_rwmtx);
+	no = erts_get_cpu_online(erts_cpuinfo);
+	erts_smp_rwmtx_runlock(&erts_cpu_bind_rwmtx);
 	if (no > 0)
 	    BIF_RET(make_small((Uint) no));
 	else {
@@ -2405,7 +2420,10 @@ BIF_RETTYPE system_info_1(BIF_ALIST_1)
 	}
     }
     else if (ERTS_IS_ATOM_STR("logical_processors_available", BIF_ARG_1)) {
-	int no = erts_get_cpu_available(erts_cpuinfo);
+	int no;
+	erts_smp_rwmtx_rlock(&erts_cpu_bind_rwmtx);
+	no = erts_get_cpu_available(erts_cpuinfo);
+	erts_smp_rwmtx_runlock(&erts_cpu_bind_rwmtx);
 	if (no > 0)
 	    BIF_RET(make_small((Uint) no));
 	else {
diff --git a/erts/emulator/beam/erl_process.c b/erts/emulator/beam/erl_process.c
index a644520442..457e283034 100644
--- a/erts/emulator/beam/erl_process.c
+++ b/erts/emulator/beam/erl_process.c
@@ -3962,7 +3962,7 @@ check_cpu_bind(ErtsSchedulerData *esdp)
 		goto unbind;
 	}
     }
-    else if (cpu_id < 0 && scheduler2cpu_map[esdp->no].bound_id >= 0) {
+    else if (cpu_id < 0) /* && scheduler2cpu_map[esdp->no].bound_id >= 0) */ {
     unbind:
 	/* Get rid of old binding */
 	res = erts_unbind_from_cpu(erts_cpuinfo);
@@ -5521,6 +5521,39 @@ late_cpu_bind_init(void)
     }
 }
 
+int
+erts_update_cpu_info(void)
+{
+    int changed;
+    erts_smp_rwmtx_rwlock(&erts_cpu_bind_rwmtx);
+    changed = erts_cpu_info_update(erts_cpuinfo);
+    if (changed) {
+	erts_cpu_topology_t *cpudata;
+	int cpudata_size;
+	erts_free(ERTS_ALC_T_CPUDATA, system_cpudata);
+
+	system_cpudata_size = erts_get_cpu_topology_size(erts_cpuinfo);
+	system_cpudata = erts_alloc(ERTS_ALC_T_CPUDATA,
+				    (sizeof(erts_cpu_topology_t)
+				     * system_cpudata_size));
+
+	if (!erts_get_cpu_topology(erts_cpuinfo, system_cpudata)
+	    || ERTS_INIT_CPU_TOPOLOGY_OK != verify_topology(system_cpudata,
+							    system_cpudata_size)) {
+	    erts_free(ERTS_ALC_T_CPUDATA, system_cpudata);
+	    system_cpudata = NULL;
+	    system_cpudata_size = 0;
+	}
+
+	create_tmp_cpu_topology_copy(&cpudata, &cpudata_size);
+	ASSERT(cpudata);
+	signal_schedulers_bind_change(cpudata, cpudata_size);
+	destroy_tmp_cpu_topology_copy(cpudata);
+    }
+    erts_smp_rwmtx_rwunlock(&erts_cpu_bind_rwmtx);
+    return changed;
+}
+
 #ifdef ERTS_SMP
 
 static void
diff --git a/erts/emulator/beam/erl_process.h b/erts/emulator/beam/erl_process.h
index c3fef6d38e..0cc4a715ad 100644
--- a/erts/emulator/beam/erl_process.h
+++ b/erts/emulator/beam/erl_process.h
@@ -1025,6 +1025,7 @@ int erts_init_scheduler_bind_type(char *how);
 #define ERTS_INIT_CPU_TOPOLOGY_MISSING			9
 
 int erts_init_cpu_topology(char *topology_str);
+int erts_update_cpu_info(void);
 
 void erts_pre_init_process(void);
 void erts_late_init_process(void);