There are a number of different reasons which can cause a partition to become invalid. A user seeing an invalid partition may not know exactly why. To help user to get a better understanding of the underlying reason, The cpuset.cpus.partition control file, when read, will now report the reason why a partition become invalid. When a partition does become invalid, reading the control file will show "root invalid (<reason>)" where <reason> is a string that describes why the partition is invalid.
Signed-off-by: Waiman Long longman@redhat.com --- kernel/cgroup/cpuset.c | 48 +++++++++++++++++++++++++++++++++++++++--- 1 file changed, 45 insertions(+), 3 deletions(-)
diff --git a/kernel/cgroup/cpuset.c b/kernel/cgroup/cpuset.c index fab31921728c..9c5ecc8d100c 100644 --- a/kernel/cgroup/cpuset.c +++ b/kernel/cgroup/cpuset.c @@ -78,6 +78,24 @@ struct fmeter { spinlock_t lock; /* guards read or write of above */ };
+/* + * Invalid partition error code + */ +enum prs_errcode { + PERR_NONE = 0, + PERR_INVCPUS, + PERR_NOCPUS, + PERR_PARENT, + PERR_HOTPLUG, +}; + +static const char * const perr_strings[] = { + [PERR_INVCPUS] = "Invalid change to cpuset.cpus", + [PERR_PARENT] = "Parent is no longer a valid partition root", + [PERR_NOCPUS] = "Parent unable to distribute cpu downstream", + [PERR_HOTPLUG] = "No cpu available due to hotplug", +}; + struct cpuset { struct cgroup_subsys_state css;
@@ -163,6 +181,9 @@ struct cpuset {
/* Handle for cpuset.cpus.partition */ struct cgroup_file partition_file; + + /* Invalid partition error code, not lock protected */ + enum prs_errcode prs_err; };
/* @@ -275,8 +296,13 @@ static inline int is_partition_root(const struct cpuset *cs) static inline void notify_partition_change(struct cpuset *cs, int old_prs, int new_prs) { - if (old_prs != new_prs) - cgroup_file_notify(&cs->partition_file); + if (old_prs == new_prs) + return; + cgroup_file_notify(&cs->partition_file); + + /* Reset prs_err if not invalid */ + if (new_prs != PRS_ERROR) + WRITE_ONCE(cs->prs_err, PERR_NONE); }
static struct cpuset top_cpuset = { @@ -1282,6 +1308,9 @@ static int update_parent_subparts_cpumask(struct cpuset *cpuset, int cmd, part_error = partition_is_populated(parent, cpuset) && cpumask_subset(parent->effective_cpus, tmp->addmask) && !cpumask_intersects(tmp->delmask, cpu_active_mask); + + if ((READ_ONCE(cpuset->prs_err) == PERR_NONE) && part_error) + WRITE_ONCE(cpuset->prs_err, PERR_INVCPUS); } else { /* * partcmd_update w/o newmask: @@ -1305,6 +1334,9 @@ static int update_parent_subparts_cpumask(struct cpuset *cpuset, int cmd, !parent->nr_subparts_cpus) || (cpumask_equal(parent->effective_cpus, tmp->addmask) && partition_is_populated(parent, cpuset)); + + if (is_partition_root(cpuset) && part_error) + WRITE_ONCE(cpuset->prs_err, PERR_NOCPUS); }
if (cmd == partcmd_update) { @@ -1478,6 +1510,7 @@ static void update_cpumasks_hier(struct cpuset *cs, struct tmpmasks *tmp, * When parent is invalid, it has to be too. */ new_prs = PRS_ERROR; + WRITE_ONCE(cp->prs_err, PERR_PARENT); break; } } @@ -2637,6 +2670,7 @@ static s64 cpuset_read_s64(struct cgroup_subsys_state *css, struct cftype *cft) static int sched_partition_show(struct seq_file *seq, void *v) { struct cpuset *cs = css_cs(seq_css(seq)); + const char *err;
switch (cs->partition_root_state) { case PRS_ENABLED: @@ -2649,7 +2683,11 @@ static int sched_partition_show(struct seq_file *seq, void *v) seq_puts(seq, "member\n"); break; case PRS_ERROR: - seq_puts(seq, "root invalid\n"); + err = perr_strings[READ_ONCE(cs->prs_err)]; + if (err) + seq_printf(seq, "root invalid (%s)\n", err); + else + seq_puts(seq, "root invalid\n"); break; } return 0; @@ -3256,6 +3294,10 @@ static void cpuset_hotplug_update_tasks(struct cpuset *cs, struct tmpmasks *tmp) spin_lock_irq(&callback_lock); cs->partition_root_state = PRS_ERROR; spin_unlock_irq(&callback_lock); + if (parent->partition_root_state == PRS_ERROR) + WRITE_ONCE(cs->prs_err, PERR_PARENT); + else + WRITE_ONCE(cs->prs_err, PERR_HOTPLUG); notify_partition_change(cs, old_prs, PRS_ERROR); } cpuset_force_rebuild();