src: read exactly two tokens from Linux THP sysfs config

There was an unexpected and hard-to-spot issue here: the /sys/kernel/mm/transparent_hugepage/enabled file contains three entries, and the std::ifstream reader was reading two values on each loop iteration, resulting in incorrect behaviour. Fixes: #37064 PR-URL: #37065 Reviewed-By: Darshan Sen <[email protected]> Reviewed-By: Rich Trott <[email protected]> Reviewed-By: James M Snell <[email protected]>
nodejs · Feb 16, 2021 · 9946c11 · 9946c11
1 parent 67c9a8e
commit 9946c11
Showing 1 changed file with 3 additions and 1 deletion.
diff --git a/src/large_pages/node_large_page.cc b/src/large_pages/node_large_page.cc
@@ -260,6 +260,8 @@ struct text_region FindNodeTextRegion() {
 bool IsTransparentHugePagesEnabled() {
   std::ifstream ifs;
 
+  // File format reference:
+  // https://git.kernel.org/pub/scm/linux/kernel/git/torvalds/linux.git/tree/mm/huge_memory.c?id=13391c60da3308ed9980de0168f74cce6c62ac1d#n163
   ifs.open("/sys/kernel/mm/transparent_hugepage/enabled");
   if (!ifs) {
     PrintWarning("could not open /sys/kernel/mm/transparent_hugepage/enabled");
@@ -268,7 +270,7 @@ bool IsTransparentHugePagesEnabled() {
 
   std::string always, madvise;
   if (ifs.is_open()) {
-    while (ifs >> always >> madvise) {}
+    ifs >> always >> madvise;
   }
   ifs.close();