admin/linux
1
0
Fork 0
mirror of https://github.com/torvalds/linux.git synced 2025-12-07 20:06:24 +00:00
Code Issues Packages Projects Releases Wiki Activity

cgroup/cpuset: Fail if isolated and nohz_full don't leave any housekeeping

Browse Source 
Currently the user can set up isolated cpus via cpuset and nohz_full in
such a way that leaves no housekeeping CPU (i.e. no CPU that is neither
domain isolated nor nohz full). This can be a problem for other
subsystems (e.g. the timer wheel imgration).

Prevent this configuration by blocking any assignation that would cause
the union of domain isolated cpus and nohz_full to covers all CPUs.

[longman: Remove isolated_cpus_should_update() and rewrite the checking
 in update_prstate() and update_parent_effective_cpumask()]

Originally-by: Gabriele Monaco <gmonaco@redhat.com>
Signed-off-by: Waiman Long <longman@redhat.com>
Reviewed-by: Chen Ridong <chenridong@huawei.com>
Signed-off-by: Tejun Heo <tj@kernel.org>
This commit is contained in:
Waiman Long
2025-11-04 23:38:45 -05:00
committed by Tejun Heo
parent 55939cf28a
commit 103b08709e
1 changed files with 73 additions and 1 deletions
Download Patch File Download Diff File Expand all files Collapse all files

74
kernel/cgroup/cpuset.c
View File

@@ -1393,6 +1393,45 @@ static bool partition_xcpus_del(int old_prs, struct cpuset *parent,
return isolcpus_updated;
}
/*
* isolated_cpus_can_update - check for isolated & nohz_full conflicts
* @add_cpus: cpu mask for cpus that are going to be isolated
* @del_cpus: cpu mask for cpus that are no longer isolated, can be NULL
* Return: false if there is conflict, true otherwise
*
* If nohz_full is enabled and we have isolated CPUs, their combination must
* still leave housekeeping CPUs.
*
* TBD: Should consider merging this function into
* prstate_housekeeping_conflict().
*/
static bool isolated_cpus_can_update(struct cpumask *add_cpus,
struct cpumask *del_cpus)
{
cpumask_var_t full_hk_cpus;
int res = true;
if (!housekeeping_enabled(HK_TYPE_KERNEL_NOISE))
return true;
if (del_cpus && cpumask_weight_and(del_cpus,
housekeeping_cpumask(HK_TYPE_KERNEL_NOISE)))
return true;
if (!alloc_cpumask_var(&full_hk_cpus, GFP_KERNEL))
return false;
cpumask_and(full_hk_cpus, housekeeping_cpumask(HK_TYPE_KERNEL_NOISE),
housekeeping_cpumask(HK_TYPE_DOMAIN));
cpumask_andnot(full_hk_cpus, full_hk_cpus, isolated_cpus);
cpumask_and(full_hk_cpus, full_hk_cpus, cpu_active_mask);
if (!cpumask_weight_andnot(full_hk_cpus, add_cpus))
res = false;
free_cpumask_var(full_hk_cpus);
return res;
}
static void update_isolation_cpumasks(bool isolcpus_updated)
{
int ret;
@@ -1551,6 +1590,9 @@ static int remote_partition_enable(struct cpuset *cs, int new_prs,
if (!cpumask_intersects(tmp->new_cpus, cpu_active_mask) ||
cpumask_subset(top_cpuset.effective_cpus, tmp->new_cpus))
return PERR_INVCPUS;
if ((new_prs == PRS_ISOLATED) &&
!isolated_cpus_can_update(tmp->new_cpus, NULL))
return PERR_HKEEPING;
spin_lock_irq(&callback_lock);
isolcpus_updated = partition_xcpus_add(new_prs, NULL, tmp->new_cpus);
@@ -1650,6 +1692,9 @@ static void remote_cpus_update(struct cpuset *cs, struct cpumask *xcpus,
else if (cpumask_intersects(tmp->addmask, subpartitions_cpus) ||
cpumask_subset(top_cpuset.effective_cpus, tmp->addmask))
cs->prs_err = PERR_NOCPUS;
else if ((prs == PRS_ISOLATED) &&
!isolated_cpus_can_update(tmp->addmask, tmp->delmask))
cs->prs_err = PERR_HKEEPING;
if (cs->prs_err)
goto invalidate;
}
@@ -1750,6 +1795,7 @@ static int update_parent_effective_cpumask(struct cpuset *cs, int cmd,
int part_error = PERR_NONE; /* Partition error? */
int isolcpus_updated = 0;
struct cpumask *xcpus = user_xcpus(cs);
int parent_prs = parent->partition_root_state;
bool nocpu;
lockdep_assert_held(&cpuset_mutex);
@@ -1813,6 +1859,10 @@ static int update_parent_effective_cpumask(struct cpuset *cs, int cmd,
if (prstate_housekeeping_conflict(new_prs, xcpus))
return PERR_HKEEPING;
if ((new_prs == PRS_ISOLATED) && (new_prs != parent_prs) &&
!isolated_cpus_can_update(xcpus, NULL))
return PERR_HKEEPING;
if (tasks_nocpu_error(parent, cs, xcpus))
return PERR_NOCPUS;
@@ -1866,6 +1916,7 @@ static int update_parent_effective_cpumask(struct cpuset *cs, int cmd,
*
* For invalid partition:
* delmask = newmask & parent->effective_xcpus
* The partition may become valid soon.
*/
if (is_partition_invalid(cs)) {
adding = false;
@@ -1880,6 +1931,23 @@ static int update_parent_effective_cpumask(struct cpuset *cs, int cmd,
deleting = cpumask_and(tmp->delmask, tmp->delmask,
parent->effective_xcpus);
}
/*
* TBD: Invalidate a currently valid child root partition may
* still break isolated_cpus_can_update() rule if parent is an
* isolated partition.
*/
if (is_partition_valid(cs) && (old_prs != parent_prs)) {
if ((parent_prs == PRS_ROOT) &&
/* Adding to parent means removing isolated CPUs */
!isolated_cpus_can_update(tmp->delmask, tmp->addmask))
part_error = PERR_HKEEPING;
if ((parent_prs == PRS_ISOLATED) &&
/* Adding to parent means adding isolated CPUs */
!isolated_cpus_can_update(tmp->addmask, tmp->delmask))
part_error = PERR_HKEEPING;
}
/*
* The new CPUs to be removed from parent's effective CPUs
* must be present.
@@ -2994,7 +3062,11 @@ static int update_prstate(struct cpuset *cs, int new_prs)
* A change in load balance state only, no change in cpumasks.
* Need to update isolated_cpus.
*/
isolcpus_updated = true;
if ((new_prs == PRS_ISOLATED) &&
!isolated_cpus_can_update(cs->effective_xcpus, NULL))
err = PERR_HKEEPING;
else
isolcpus_updated = true;
} else {
/*
* Switching back to member is always allowed even if it