8253435: Cgroup: 'stomping of _mount_path' crash if manually mounted cpusets exist

Backport-of: 0054c15

Author: Jonathan Dowland

src/hotspot/os/linux/cgroupSubsystem_linux.cpp

@@ -302,8 +302,22 @@ bool CgroupSubsystemFactory::determine_type(CgroupInfo* cg_infos,
           cg_infos[MEMORY_IDX]._root_mount_path = os::strdup(tmproot);
           cg_infos[MEMORY_IDX]._data_complete = true;
         } else if (strcmp(token, "cpuset") == 0) {
-          assert(cg_infos[CPUSET_IDX]._mount_path == NULL, "stomping of _mount_path");
-          cg_infos[CPUSET_IDX]._mount_path = os::strdup(tmpmount);
+          if (cg_infos[CPUSET_IDX]._mount_path != NULL) {
+            // On some systems duplicate cpuset controllers get mounted in addition to
+            // the main cgroup controllers most likely under /sys/fs/cgroup. In that
+            // case pick the one under /sys/fs/cgroup and discard others.
+            if (strstr(cg_infos[CPUSET_IDX]._mount_path, "/sys/fs/cgroup") != cg_infos[CPUSET_IDX]._mount_path) {
+              log_warning(os, container)("Duplicate cpuset controllers detected. Picking %s, skipping %s.",
+                                         tmpmount, cg_infos[CPUSET_IDX]._mount_path);
+              os::free(cg_infos[CPUSET_IDX]._mount_path);
+              cg_infos[CPUSET_IDX]._mount_path = os::strdup(tmpmount);
+            } else {
+              log_warning(os, container)("Duplicate cpuset controllers detected. Picking %s, skipping %s.",
+                                         cg_infos[CPUSET_IDX]._mount_path, tmpmount);
+            }
+          } else {
+            cg_infos[CPUSET_IDX]._mount_path = os::strdup(tmpmount);
+          }
           cg_infos[CPUSET_IDX]._root_mount_path = os::strdup(tmproot);
           cg_infos[CPUSET_IDX]._data_complete = true;
         } else if (strcmp(token, "cpu") == 0) {

test/hotspot/jtreg/containers/cgroup/CgroupSubsystemFactory.java

@@ -61,6 +61,8 @@ public class CgroupSubsystemFactory {
     private Path cgroupv1CgInfoNonZeroHierarchy;
     private Path cgroupv1MntInfoNonZeroHierarchyOtherOrder;
     private Path cgroupv1MntInfoNonZeroHierarchy;
+    private Path cgroupv1MntInfoDoubleCpuset;
+    private Path cgroupv1MntInfoDoubleCpuset2;
     private String mntInfoEmpty = "";
     private Path cgroupV1SelfCgroup;
     private Path cgroupV2SelfCgroup;
@@ -103,11 +105,14 @@ public class CgroupSubsystemFactory {
             "41 30 0:37 / /sys/fs/cgroup/devices rw,nosuid,nodev,noexec,relatime shared:13 - cgroup none rw,seclabel,devices\n" +
             "42 30 0:38 / /sys/fs/cgroup/cpuset rw,nosuid,nodev,noexec,relatime shared:14 - cgroup none rw,seclabel,cpuset\n" +
             "43 30 0:39 / /sys/fs/cgroup/blkio rw,nosuid,nodev,noexec,relatime shared:15 - cgroup none rw,seclabel,blkio\n" +
-            "44 30 0:40 / /sys/fs/cgroup/freezer rw,nosuid,nodev,noexec,relatime shared:16 - cgroup none rw,seclabel,freezer";
+            "44 30 0:40 / /sys/fs/cgroup/freezer rw,nosuid,nodev,noexec,relatime shared:16 - cgroup none rw,seclabel,freezer\n";
     private String mntInfoHybridRest = cgroupv1MountInfoLineMemory + mntInfoHybridStub;
     private String mntInfoHybridMissingMemory = mntInfoHybridStub;
     private String mntInfoHybrid = cgroupV2LineHybrid + mntInfoHybridRest;
     private String mntInfoHybridFlippedOrder = mntInfoHybridRest + cgroupV2LineHybrid;
+    private String mntInfoCgroupv1MoreCpusetLine = "121 32 0:37 / /cpusets rw,relatime shared:69 - cgroup none rw,cpuset\n";
+    private String mntInfoCgroupv1DoubleCpuset = mntInfoCgroupv1MoreCpusetLine + mntInfoHybrid;
+    private String mntInfoCgroupv1DoubleCpuset2 =  mntInfoHybrid + mntInfoCgroupv1MoreCpusetLine;
     private String cgroupsNonZeroHierarchy =
             "#subsys_name hierarchy   num_cgroups enabled\n" +
             "cpuset  3   1   1\n" +
@@ -158,6 +163,12 @@ private void setup() {
 
             cgroupV2MntInfoMissingCgroupv2 = Paths.get(existingDirectory.toString(), "mnt_info_missing_cgroup2");
             Files.writeString(cgroupV2MntInfoMissingCgroupv2, mntInfoHybridStub);
+
+            cgroupv1MntInfoDoubleCpuset = Paths.get(existingDirectory.toString(), "mnt_info_cgroupv1_double_cpuset");
+            Files.writeString(cgroupv1MntInfoDoubleCpuset, mntInfoCgroupv1DoubleCpuset);
+
+            cgroupv1MntInfoDoubleCpuset2 = Paths.get(existingDirectory.toString(), "mnt_info_cgroupv1_double_cpuset2");
+            Files.writeString(cgroupv1MntInfoDoubleCpuset2, mntInfoCgroupv1DoubleCpuset2);
         } catch (IOException e) {
             throw new RuntimeException(e);
         }
@@ -175,6 +186,16 @@ private boolean isValidCgroup(int value) {
         return value == CGROUPS_V1 || value == CGROUPS_V2;
     }
 
+    public void testCgroupv1MultipleCpusetMounts(WhiteBox wb, Path mountInfo) {
+        String procCgroups = cgroupv1CgInfoNonZeroHierarchy.toString();
+        String procSelfCgroup = cgroupV1SelfCgroup.toString();
+        String procSelfMountinfo = mountInfo.toString();
+        int retval = wb.validateCgroup(procCgroups, procSelfCgroup, procSelfMountinfo);
+        Asserts.assertEQ(CGROUPS_V1, retval, "Multiple cpuset controllers, but only one in /sys/fs/cgroup");
+        Asserts.assertTrue(isValidCgroup(retval));
+        System.out.println("testCgroupv1MultipleCpusetMounts PASSED!");
+    }
+
     public void testCgroupv1NoMounts(WhiteBox wb) {
         String procCgroups = cgroupv1CgInfoZeroHierarchy.toString();
         String procSelfCgroup = cgroupV1SelfCgroup.toString();
@@ -247,6 +268,8 @@ public static void main(String[] args) throws Exception {
             test.testCgroupV1HybridMntInfoOrder(wb);
             test.testCgroupv1MissingMemoryController(wb);
             test.testCgroupv2NoCgroup2Fs(wb);
+            test.testCgroupv1MultipleCpusetMounts(wb, test.cgroupv1MntInfoDoubleCpuset);
+            test.testCgroupv1MultipleCpusetMounts(wb, test.cgroupv1MntInfoDoubleCpuset2);
         } finally {
             test.teardown();
         }