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cgroup/cpuset: Show invalid partition reason string

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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>
Signed-off-by: Tejun Heo <tj@kernel.org>
This commit is contained in:
Waiman Long 2022-09-01 16:57:41 -04:00 committed by Tejun Heo
parent f28e22441f
commit 7476a636d3
1 changed files with 75 additions and 18 deletions
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93
kernel/cgroup/cpuset.c
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@ -86,6 +86,30 @@ struct fmeter {
spinlock_t lock; /* guards read or write of above */
};
/*
* Invalid partition error code
*/
enum prs_errcode {
PERR_NONE = 0,
PERR_INVCPUS,
PERR_INVPARENT,
PERR_NOTPART,
PERR_NOTEXCL,
PERR_NOCPUS,
PERR_HOTPLUG,
PERR_CPUSEMPTY,
};
static const char * const perr_strings[] = {
[PERR_INVCPUS] = "Invalid cpu list in cpuset.cpus",
[PERR_INVPARENT] = "Parent is an invalid partition root",
[PERR_NOTPART] = "Parent is not a partition root",
[PERR_NOTEXCL] = "Cpu list in cpuset.cpus not exclusive",
[PERR_NOCPUS] = "Parent unable to distribute cpu downstream",
[PERR_HOTPLUG] = "No cpu available due to hotplug",
[PERR_CPUSEMPTY] = "cpuset.cpus is empty",
};
struct cpuset {
struct cgroup_subsys_state css;
@ -169,6 +193,9 @@ struct cpuset {
int use_parent_ecpus;
int child_ecpus_count;
/* Invalid partition error code, not lock protected */
enum prs_errcode prs_err;
/* Handle for cpuset.cpus.partition */
struct cgroup_file partition_file;
};
@ -298,6 +325,10 @@ static inline void notify_partition_change(struct cpuset *cs, int old_prs)
if (old_prs == cs->partition_root_state)
return;
cgroup_file_notify(&cs->partition_file);
/* Reset prs_err if not invalid */
if (is_partition_valid(cs))
WRITE_ONCE(cs->prs_err, PERR_NONE);
}
static struct cpuset top_cpuset = {
@ -1235,7 +1266,7 @@ static int update_flag(cpuset_flagbits_t bit, struct cpuset *cs,
* @cmd: Partition root state change command
* @newmask: Optional new cpumask for partcmd_update
* @tmp: Temporary addmask and delmask
* Return: 0 or -1 (error)
* Return: 0 or a partition root state error code
*
* For partcmd_enable, the cpuset is being transformed from a non-partition
* root to a partition root. The cpus_allowed mask of the given cpuset will
@ -1261,7 +1292,7 @@ static int update_flag(cpuset_flagbits_t bit, struct cpuset *cs,
*
* The partcmd_update command is used by update_cpumasks_hier() with newmask
* NULL and update_cpumask() with newmask set. The callers won't check for
* error and so partition_root_state will be updated directly.
* error and so partition_root_state and prs_error will be updated directly.
*/
static int update_parent_subparts_cpumask(struct cpuset *cs, int cmd,
struct cpumask *newmask,
@ -1271,7 +1302,7 @@ static int update_parent_subparts_cpumask(struct cpuset *cs, int cmd,
int adding; /* Moving cpus from effective_cpus to subparts_cpus */
int deleting; /* Moving cpus from subparts_cpus to effective_cpus */
int old_prs, new_prs;
bool part_error = false; /* Partition error? */
int part_error = PERR_NONE; /* Partition error? */
percpu_rwsem_assert_held(&cpuset_rwsem);
@ -1280,10 +1311,13 @@ static int update_parent_subparts_cpumask(struct cpuset *cs, int cmd,
* The new cpumask, if present, or the current cpus_allowed must
* not be empty.
*/
if (!is_partition_valid(parent) ||
(newmask && cpumask_empty(newmask)) ||
if (!is_partition_valid(parent)) {
return is_partition_invalid(parent)
? PERR_INVPARENT : PERR_NOTPART;
}
if ((newmask && cpumask_empty(newmask)) ||
(!newmask && cpumask_empty(cs->cpus_allowed)))
return -1;
return PERR_CPUSEMPTY;
/*
* new_prs will only be changed for the partcmd_update command.
@ -1296,7 +1330,7 @@ static int update_parent_subparts_cpumask(struct cpuset *cs, int cmd,
* doesn't overlap parent's cpus_allowed.
*/
if (!cpumask_intersects(cs->cpus_allowed, parent->cpus_allowed))
return -1;
return PERR_INVCPUS;
/*
* A parent can be left with no CPU as long as there is no
@ -1304,7 +1338,7 @@ static int update_parent_subparts_cpumask(struct cpuset *cs, int cmd,
*/
if (!cpumask_intersects(cs->cpus_allowed, parent->effective_cpus) &&
partition_is_populated(parent, cs))
return -1;
return PERR_NOCPUS;
cpumask_copy(tmp->addmask, cs->cpus_allowed);
adding = true;
@ -1341,7 +1375,7 @@ static int update_parent_subparts_cpumask(struct cpuset *cs, int cmd,
cpumask_subset(parent->effective_cpus, tmp->addmask) &&
!cpumask_intersects(tmp->delmask, cpu_active_mask) &&
partition_is_populated(parent, cs)) {
part_error = true;
part_error = PERR_NOCPUS;
adding = false;
deleting = cpumask_and(tmp->delmask, cs->cpus_allowed,
parent->subparts_cpus);
@ -1373,7 +1407,7 @@ static int update_parent_subparts_cpumask(struct cpuset *cs, int cmd,
(adding &&
cpumask_subset(parent->effective_cpus, tmp->addmask) &&
partition_is_populated(parent, cs))) {
part_error = true;
part_error = PERR_NOCPUS;
adding = false;
}
@ -1382,6 +1416,8 @@ static int update_parent_subparts_cpumask(struct cpuset *cs, int cmd,
deleting = cpumask_and(tmp->delmask, cs->cpus_allowed,
parent->subparts_cpus);
}
if (part_error)
WRITE_ONCE(cs->prs_err, part_error);
if (cmd == partcmd_update) {
/*
@ -1412,7 +1448,7 @@ static int update_parent_subparts_cpumask(struct cpuset *cs, int cmd,
if (old_prs != new_prs) {
if (is_prs_invalid(old_prs) && !is_cpu_exclusive(cs) &&
(update_flag(CS_CPU_EXCLUSIVE, cs, 1) < 0))
return -1;
return PERR_NOTEXCL;
if (is_prs_invalid(new_prs) && is_cpu_exclusive(cs))
update_flag(CS_CPU_EXCLUSIVE, cs, 0);
}
@ -1547,6 +1583,9 @@ update_parent_subparts:
*/
if (is_partition_valid(cp))
new_prs = -cp->partition_root_state;
WRITE_ONCE(cp->prs_err,
is_partition_invalid(parent)
? PERR_INVPARENT : PERR_NOTPART);
break;
}
}
@ -2121,13 +2160,13 @@ out:
* update_prstate - update partition_root_state
* @cs: the cpuset to update
* @new_prs: new partition root state
* Return: 0 if successful, < 0 if error
* Return: 0 if successful, != 0 if error
*
* Call with cpuset_rwsem held.
*/
static int update_prstate(struct cpuset *cs, int new_prs)
{
int err = 0, old_prs = cs->partition_root_state;
int err = PERR_NONE, old_prs = cs->partition_root_state;
bool sched_domain_rebuilt = false;
struct cpuset *parent = parent_cs(cs);
struct tmpmasks tmpmask;
@ -2154,13 +2193,15 @@ static int update_prstate(struct cpuset *cs, int new_prs)
* cannot be empty.
*/
if (cpumask_empty(cs->cpus_allowed)) {
err = 1;
err = PERR_CPUSEMPTY;
goto out;
}
err = update_flag(CS_CPU_EXCLUSIVE, cs, 1);
if (err)
if (err) {
err = PERR_NOTEXCL;
goto out;
}
err = update_parent_subparts_cpumask(cs, partcmd_enable,
NULL, &tmpmask);
@ -2730,6 +2771,7 @@ 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, *type = NULL;
switch (cs->partition_root_state) {
case PRS_ROOT:
@ -2742,9 +2784,17 @@ static int sched_partition_show(struct seq_file *seq, void *v)
seq_puts(seq, "member\n");
break;
case PRS_INVALID_ROOT:
seq_puts(seq, "root invalid\n");
break;
type = "root";
fallthrough;
case PRS_INVALID_ISOLATED:
if (!type)
type = "isolated";
err = perr_strings[READ_ONCE(cs->prs_err)];
if (err)
seq_printf(seq, "%s invalid (%s)\n", type, err);
else
seq_printf(seq, "%s invalid\n", type);
break;
seq_puts(seq, "isolated invalid\n");
break;
}
@ -3335,7 +3385,7 @@ retry:
*/
if (is_partition_valid(cs) && (!parent->nr_subparts_cpus ||
(cpumask_empty(&new_cpus) && partition_is_populated(cs, NULL)))) {
int old_prs;
int old_prs, parent_prs;
update_parent_subparts_cpumask(cs, partcmd_disable, NULL, tmp);
if (cs->nr_subparts_cpus) {
@ -3347,10 +3397,17 @@ retry:
}
old_prs = cs->partition_root_state;
parent_prs = parent->partition_root_state;
if (is_partition_valid(cs)) {
spin_lock_irq(&callback_lock);
make_partition_invalid(cs);
spin_unlock_irq(&callback_lock);
if (is_prs_invalid(parent_prs))
WRITE_ONCE(cs->prs_err, PERR_INVPARENT);
else if (!parent_prs)
WRITE_ONCE(cs->prs_err, PERR_NOTPART);
else
WRITE_ONCE(cs->prs_err, PERR_HOTPLUG);
notify_partition_change(cs, old_prs);
}
cpuset_force_rebuild();