If /sys/fs/cgroup exists and it is type cgroup2, deadline mounts it a
second time as cgroup.
systemd is creating cgroup2 for logins and this can hang the machine and
not allow logins.
Fix this by:
If /sys/fs/cgroup exists, then use it for deadline_test.
If it exists but the type is not recognized, exit with an error.
Do not simply mount is as type cgroup.
TODO: If the file doesn't exit but cgroups are supported in the kernel,
the file could be created and mounted.
Signed-off-by: John Kacur <jkacur@xxxxxxxxxx>
---
src/sched_deadline/deadline_test.c | 39 ++++++++++++++++++++++++------
1 file changed, 32 insertions(+), 7 deletions(-)
diff --git a/src/sched_deadline/deadline_test.c b/src/sched_deadline/deadline_test.c
index b7e1e045b57c..11d669025425 100644
--- a/src/sched_deadline/deadline_test.c
+++ b/src/sched_deadline/deadline_test.c
@@ -518,6 +518,32 @@ static int mounted(const char *path, long magic)
#define CGROUP_PATH "/sys/fs/cgroup"
#define CPUSET_PATH CGROUP_PATH "/cpuset"
+/**
+ * cgroup_mounted - test if the path /sys/fs/cgroup exists
+ * and is a supported type
+ *
+ * Returns -1 if the path does not exist
+ * Returns 0 if the path exists but is not a cgroup type
+ * Returns 1 if the path exists and supports cgroups
+ */
+static int cgroup_mounted(void)
+{
+ int ret;
+
+ ret = mounted(CGROUP_PATH, TMPFS_MAGIC);
+ if (ret == -1)
+ return -1; /* path doesn't exist */
+ if (ret == 1)
+ return 1; /* tmpfs */
+ ret = mounted(CGROUP_PATH, CGROUP_SUPER_MAGIC);
+ if (ret == 1)
+ return 1; /* cgroup v1 */
+ ret = mounted(CGROUP_PATH, CGROUP2_SUPER_MAGIC);
+ if (ret == 1)
+ return 1;
+ return 0; /* path exists but type is not recognized */
+}
+
/**
* open_cpuset - open a file (usually a cpuset file)
* @path: The path of the directory the file is in
@@ -568,14 +594,13 @@ static int mount_cpuset(void)
int fd;
/* Check if cgroups is already mounted. */
- ret = mounted(CGROUP_PATH, TMPFS_MAGIC);
- if (ret < 0)
+ ret = cgroup_mounted();
+ if (ret < 0) /* /sys/fs/cgroup doesn't exist */
return ret;
- if (!ret) {
- ret = mount("cgroup_root", CGROUP_PATH, "tmpfs", 0, NULL);
- if (ret < 0)
- return ret;
- }
+
+ if (!ret) /* /sys/fs/cgroup exists, but we don't recognize the type */
+ return -1;
+
ret = stat(CPUSET_PATH, &st);
if (ret < 0) {
ret = mkdir(CPUSET_PATH, 0755);
--
2.31.1
