Revert "libprocessgroup: Add a function to remove only empty process groups"

Revert this CL because it tests whether or not cgroup.procs files are
empty with the stat() system call and because the cgroup filesystem
always reports st_size == 0. Rename RemoveUidCgroups() into
RemoveEmptyUidCgroups().

Change-Id: I4de6f16c814c4b47d8d74c8045f0c1ee71975ac0
Signed-off-by: Bart Van Assche <bvanassche@google.com>
diff --git a/libprocessgroup/include/processgroup/processgroup.h b/libprocessgroup/include/processgroup/processgroup.h
index a319c63..9107838 100644
--- a/libprocessgroup/include/processgroup/processgroup.h
+++ b/libprocessgroup/include/processgroup/processgroup.h
@@ -87,7 +87,6 @@
 bool setProcessGroupSoftLimit(uid_t uid, int initialPid, int64_t softLimitInBytes);
 bool setProcessGroupLimit(uid_t uid, int initialPid, int64_t limitInBytes);
 
-void removeAllProcessGroups(void);
 void removeAllEmptyProcessGroups(void);
 
 // Provides the path for an attribute in a specific process group
diff --git a/libprocessgroup/processgroup.cpp b/libprocessgroup/processgroup.cpp
index d352f0e..b4482d0 100644
--- a/libprocessgroup/processgroup.cpp
+++ b/libprocessgroup/processgroup.cpp
@@ -233,7 +233,7 @@
     return ret;
 }
 
-static bool RemoveUidCgroups(const std::string& uid_path, bool empty_only) {
+static bool RemoveEmptyUidCgroups(const std::string& uid_path) {
     std::unique_ptr<DIR, decltype(&closedir)> uid(opendir(uid_path.c_str()), closedir);
     bool empty = true;
     if (uid != NULL) {
@@ -248,21 +248,6 @@
             }
 
             auto path = StringPrintf("%s/%s", uid_path.c_str(), dir->d_name);
-            if (empty_only) {
-                struct stat st;
-                auto procs_file = StringPrintf("%s/%s", path.c_str(),
-                                               PROCESSGROUP_CGROUP_PROCS_FILE);
-                if (stat(procs_file.c_str(), &st) == -1) {
-                    PLOG(ERROR) << "Failed to get stats for " << procs_file;
-                    continue;
-                }
-                if (st.st_size > 0) {
-                    // skip non-empty groups
-                    LOG(VERBOSE) << "Skipping non-empty group " << path;
-                    empty = false;
-                    continue;
-                }
-            }
             LOG(VERBOSE) << "Removing " << path;
             if (rmdir(path.c_str()) == -1) {
                 if (errno != EBUSY) {
@@ -275,7 +260,9 @@
     return empty;
 }
 
-static void removeAllProcessGroupsInternal(bool empty_only) {
+void removeAllEmptyProcessGroups() {
+    LOG(VERBOSE) << "removeAllEmptyProcessGroups()";
+
     std::vector<std::string> cgroups;
     std::string path, memcg_apps_path;
 
@@ -302,7 +289,7 @@
                 }
 
                 auto path = StringPrintf("%s/%s", cgroup_root_path.c_str(), dir->d_name);
-                if (!RemoveUidCgroups(path, empty_only)) {
+                if (!RemoveEmptyUidCgroups(path)) {
                     LOG(VERBOSE) << "Skip removing " << path;
                     continue;
                 }
@@ -315,16 +302,6 @@
     }
 }
 
-void removeAllProcessGroups() {
-    LOG(VERBOSE) << "removeAllProcessGroups()";
-    removeAllProcessGroupsInternal(false);
-}
-
-void removeAllEmptyProcessGroups() {
-    LOG(VERBOSE) << "removeAllEmptyProcessGroups()";
-    removeAllProcessGroupsInternal(true);
-}
-
 /**
  * Process groups are primarily created by the Zygote, meaning that uid/pid groups are created by
  * the user root. Ownership for the newly created cgroup and all of its files must thus be