erts: Activate staged code in a thread safe way

Activation of staged code is scheduled for a later moment when
all schedulers have done a full memory barrier. This allow
them to read active code index while executing without any
memory barriers at all.

1 files changed, 51 insertions, 2 deletions

diff --git a/erts/emulator/beam/erl_process.c b/erts/emulator/beam/erl_process.c
index 44a99e1f84..aaee951107 100644
--- a/erts/emulator/beam/erl_process.c
+++ b/erts/emulator/beam/erl_process.c
@@ -366,6 +366,9 @@ dbg_chk_aux_work_val(erts_aint32_t value)
 #ifdef ERTS_SMP_SCHEDULERS_NEED_TO_CHECK_CHILDREN
     valid |= ERTS_SSI_AUX_WORK_CHECK_CHILDREN;
 #endif
+#ifdef ERTS_SMP
+    valid |= ERTS_SSI_AUX_WORK_CODE_IX_ACTIVATION;
+#endif
 
     if (~valid & value)
 	erl_exit(ERTS_ABORT_EXIT,
@@ -861,7 +864,7 @@ set_aux_work_flags_wakeup_nob(ErtsSchedulerSleepInfo *ssi,
     }
 }
 
-#if 0 /* Currently not used */
+#ifdef ERTS_SMP
 
 static ERTS_INLINE void
 set_aux_work_flags_wakeup_relb(ErtsSchedulerSleepInfo *ssi,
@@ -882,7 +885,7 @@ set_aux_work_flags_wakeup_relb(ErtsSchedulerSleepInfo *ssi,
     }
 }
 
-#endif
+#endif /* ERTS_SMP */
 
 static ERTS_INLINE erts_aint32_t
 set_aux_work_flags(ErtsSchedulerSleepInfo *ssi, erts_aint32_t flgs)
@@ -1145,7 +1148,49 @@ handle_async_ready_clean(ErtsAuxWorkData *awdp,
     }
 }
 
+#endif /* ERTS_USE_ASYNC_READY_Q */
+
+#ifdef ERTS_SMP
+void
+erts_notify_code_ix_activation(Process* p, ErtsThrPrgrVal later)
+{
+    ErtsAuxWorkData* awdp = &p->scheduler_data->aux_work_data;
+    ASSERT(awdp->code_ix_activation.code_stager == NULL);
+    awdp->code_ix_activation.code_stager = p;
+    awdp->code_ix_activation.thr_prgr = later;
+    erts_smp_proc_inc_refc(p);
+    set_aux_work_flags_wakeup_relb(p->scheduler_data->ssi,
+				   ERTS_SSI_AUX_WORK_CODE_IX_ACTIVATION);
+}
+
+static erts_aint32_t
+handle_code_ix_activation(ErtsAuxWorkData *awdp, erts_aint32_t aux_work)
+{
+    Process* p;
+    if (!erts_thr_progress_has_reached(awdp->code_ix_activation.thr_prgr)) {
+	return aux_work & ~ERTS_SSI_AUX_WORK_CODE_IX_ACTIVATION;
+    }
+    unset_aux_work_flags(awdp->ssi, ERTS_SSI_AUX_WORK_CODE_IX_ACTIVATION);
+    p = awdp->code_ix_activation.code_stager;
+    ASSERT(p);
+#ifdef DEBUG
+    awdp->code_ix_activation.code_stager = NULL;
 #endif
+    erts_smp_proc_lock(p, ERTS_PROC_LOCK_STATUS);
+    if (!ERTS_PROC_IS_EXITING(p)) {
+	erts_activate_staging_code_ix();
+	erts_resume(p, ERTS_PROC_LOCK_STATUS);
+	erts_smp_proc_unlock(p, ERTS_PROC_LOCK_STATUS);
+    }
+    else {
+	erts_smp_proc_unlock(p, ERTS_PROC_LOCK_STATUS);
+	erts_abort_staging_code_ix();
+    }
+    erts_unlock_code_ix();
+    erts_smp_proc_dec_refc(p);
+    return aux_work & ~ERTS_SSI_AUX_WORK_CODE_IX_ACTIVATION;
+}
+#endif /* ERTS_SMP */
 
 static ERTS_INLINE erts_aint32_t
 handle_fix_alloc(ErtsAuxWorkData *awdp, erts_aint32_t aux_work)
@@ -1451,6 +1496,10 @@ handle_aux_work(ErtsAuxWorkData *awdp, erts_aint32_t orig_aux_work)
 		    handle_mseg_cache_check);
 #endif
 
+#ifdef ERTS_SMP
+    HANDLE_AUX_WORK(ERTS_SSI_AUX_WORK_CODE_IX_ACTIVATION,
+		    handle_code_ix_activation);
+#endif
     ERTS_DBG_CHK_AUX_WORK_VAL(aux_work);
 
     return aux_work;