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From 8100a3ae8c6abff99fb512d126055f4b603f4517 Mon Sep 17 00:00:00 2001
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From: John Kacur <jkacur@redhat.com>
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Date: Thu, 18 Nov 2021 13:48:10 -0500
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Subject: [PATCH 1/2] rt-tests: deadline_test: Fix double mount of cgroups
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If /sys/fs/cgroup exists and it is type cgroup2, deadline mounts it a
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second time as cgroup.
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systemd is creating cgroup2 for logins and this can hang the machine and
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not allow logins.
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Fix this by:
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If /sys/fs/cgroup exists, then use it for deadline_test.
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If it exists but the type is not recognized, exit with an error.
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Do not simply mount it as type cgroup.
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TODO: If the file doesn't exit but cgroups are supported in the kernel,
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the file could be created and mounted.
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Signed-off-by: John Kacur <jkacur@redhat.com>
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---
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src/sched_deadline/deadline_test.c | 39 ++++++++++++++++++++++++------
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1 file changed, 32 insertions(+), 7 deletions(-)
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diff --git a/src/sched_deadline/deadline_test.c b/src/sched_deadline/deadline_test.c
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index b7e1e045b57c..11d669025425 100644
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--- a/src/sched_deadline/deadline_test.c
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+++ b/src/sched_deadline/deadline_test.c
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@@ -518,6 +518,32 @@ static int mounted(const char *path, long magic)
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#define CGROUP_PATH "/sys/fs/cgroup"
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#define CPUSET_PATH CGROUP_PATH "/cpuset"
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+/**
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+ * cgroup_mounted - test if the path /sys/fs/cgroup exists
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+ * and is a supported type
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+ *
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+ * Returns -1 if the path does not exist
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+ * Returns 0 if the path exists but is not a cgroup type
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+ * Returns 1 if the path exists and supports cgroups
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+ */
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+static int cgroup_mounted(void)
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+{
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+ int ret;
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+
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+ ret = mounted(CGROUP_PATH, TMPFS_MAGIC);
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+ if (ret == -1)
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+ return -1; /* path doesn't exist */
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+ if (ret == 1)
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+ return 1; /* tmpfs */
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+ ret = mounted(CGROUP_PATH, CGROUP_SUPER_MAGIC);
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+ if (ret == 1)
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+ return 1; /* cgroup v1 */
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+ ret = mounted(CGROUP_PATH, CGROUP2_SUPER_MAGIC);
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+ if (ret == 1)
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+ return 1;
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+ return 0; /* path exists but type is not recognized */
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+}
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+
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/**
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* open_cpuset - open a file (usually a cpuset file)
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* @path: The path of the directory the file is in
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@@ -568,14 +594,13 @@ static int mount_cpuset(void)
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int fd;
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/* Check if cgroups is already mounted. */
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- ret = mounted(CGROUP_PATH, TMPFS_MAGIC);
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- if (ret < 0)
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+ ret = cgroup_mounted();
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+ if (ret < 0) /* /sys/fs/cgroup doesn't exist */
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return ret;
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- if (!ret) {
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- ret = mount("cgroup_root", CGROUP_PATH, "tmpfs", 0, NULL);
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- if (ret < 0)
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- return ret;
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- }
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+
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+ if (!ret) /* /sys/fs/cgroup exists, but we don't recognize the type */
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+ return -1;
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+
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ret = stat(CPUSET_PATH, &st);
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if (ret < 0) {
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ret = mkdir(CPUSET_PATH, 0755);
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--
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2.31.1
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