From 70999283156f527c5aea6dee57a3d14989a9903a Mon Sep 17 00:00:00 2001
From: Ben Gamari <ben@smart-cactus.org>
Date: Wed, 9 Nov 2022 12:39:47 -0500
Subject: rts: Introduce getNumCapabilities

And ensure accesses to n_capabilities are atomic (although with relaxed
ordering). This is necessary as RTS API callers may concurrently call
into the RTS without holding a capability.
---
 rts/Capability.c | 18 +++++++++---------
 1 file changed, 9 insertions(+), 9 deletions(-)

(limited to 'rts/Capability.c')

diff --git a/rts/Capability.c b/rts/Capability.c
index afe21fcb46..bf20d991e8 100644
--- a/rts/Capability.c
+++ b/rts/Capability.c
@@ -131,7 +131,7 @@ findSpark (Capability *cap)
           retry = true;
       }
 
-      if (n_capabilities == 1) { return NULL; } // makes no sense...
+      if (getNumCapabilities() == 1) { return NULL; } // makes no sense...
 
       debugTrace(DEBUG_sched,
                  "cap %d: Trying to steal work from other capabilities",
@@ -139,7 +139,7 @@ findSpark (Capability *cap)
 
       /* visit cap.s 0..n-1 in sequence until a theft succeeds. We could
       start at a random place instead of 0 as well.  */
-      for ( i=0 ; i < n_capabilities ; i++ ) {
+      for ( i=0 ; i < getNumCapabilities() ; i++ ) {
           robbed = capabilities[i];
           if (cap == robbed)  // ourselves...
               continue;
@@ -182,7 +182,7 @@ anySparks (void)
 {
     uint32_t i;
 
-    for (i=0; i < n_capabilities; i++) {
+    for (i=0; i < getNumCapabilities(); i++) {
         if (!emptySparkPoolCap(capabilities[i])) {
             return true;
         }
@@ -464,7 +464,7 @@ moreCapabilities (uint32_t from USED_IF_THREADS, uint32_t to USED_IF_THREADS)
 void contextSwitchAllCapabilities(void)
 {
     uint32_t i;
-    for (i=0; i < n_capabilities; i++) {
+    for (i=0; i < getNumCapabilities(); i++) {
         contextSwitchCapability(capabilities[i], true);
     }
 }
@@ -472,7 +472,7 @@ void contextSwitchAllCapabilities(void)
 void interruptAllCapabilities(void)
 {
     uint32_t i;
-    for (i=0; i < n_capabilities; i++) {
+    for (i=0; i < getNumCapabilities(); i++) {
         interruptCapability(capabilities[i]);
     }
 }
@@ -1249,7 +1249,7 @@ void
 shutdownCapabilities(Task *task, bool safe)
 {
     uint32_t i;
-    for (i=0; i < n_capabilities; i++) {
+    for (i=0; i < getNumCapabilities(); i++) {
         ASSERT(task->incall->tso == NULL);
         shutdownCapability(capabilities[i], task, safe);
     }
@@ -1276,7 +1276,7 @@ freeCapabilities (void)
 {
 #if defined(THREADED_RTS)
     uint32_t i;
-    for (i=0; i < n_capabilities; i++) {
+    for (i=0; i < getNumCapabilities(); i++) {
         freeCapability(capabilities[i]);
         if (capabilities[i] != &MainCapability)
             stgFree(capabilities[i]);
@@ -1332,7 +1332,7 @@ void
 markCapabilities (evac_fn evac, void *user)
 {
     uint32_t n;
-    for (n = 0; n < n_capabilities; n++) {
+    for (n = 0; n < getNumCapabilities(); n++) {
         markCapability(evac, user, capabilities[n], false);
     }
 }
@@ -1344,7 +1344,7 @@ bool checkSparkCountInvariant (void)
     StgWord64 remaining = 0;
     uint32_t i;
 
-    for (i = 0; i < n_capabilities; i++) {
+    for (i = 0; i < getNumCapabilities(); i++) {
         sparks.created   += capabilities[i]->spark_stats.created;
         sparks.dud       += capabilities[i]->spark_stats.dud;
         sparks.overflowed+= capabilities[i]->spark_stats.overflowed;
-- 
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