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cgroup/cpuset: record DL BW alloc CPU for attach rollback

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cpuset_can_attach() allocates DL bandwidth only when migrating
deadline tasks to a disjoint CPU mask, but cpuset_cancel_attach()
rolls back based only on nr_migrate_dl_tasks. This makes the DL
bandwidth alloc/free paths asymmetric: rollback can call dl_bw_free()
even when no dl_bw_alloc() was done.

Rollback also needs to undo the reservation against the same CPU/root
domain that was charged. Record the CPU used by dl_bw_alloc() and use
that state in cpuset_cancel_attach(). If no allocation happened,
dl_bw_cpu stays at -1 and rollback skips dl_bw_free(). If allocation
did happen, bandwidth is returned to the same CPU/root domain.

Successful attach paths are unchanged. This only fixes failed attach
rollback accounting.

Fixes: 2ef269ef1a ("cgroup/cpuset: Free DL BW in case can_attach() fails")
Signed-off-by: Guopeng Zhang <zhangguopeng@kylinos.cn>
Reviewed-by: Waiman Long <longman@redhat.com>
Signed-off-by: Tejun Heo <tj@kernel.org>
This commit is contained in:
Guopeng Zhang
2026-04-17 11:37:41 +08:00
committed by Tejun Heo
parent c802f460dd
commit 41d701ddc3
2 changed files with 14 additions and 4 deletions
Download Patch File Download Diff File Expand all files Collapse all files

5
kernel/cgroup/cpuset-internal.h
View File

@@ -168,6 +168,11 @@ struct cpuset {
int nr_deadline_tasks;
int nr_migrate_dl_tasks;
u64 sum_migrate_dl_bw;
/*
* CPU used for temporary DL bandwidth allocation during attach;
* -1 if no DL bandwidth was allocated in the current attach.
*/
int dl_bw_cpu;
/* Invalid partition error code, not lock protected */
enum prs_errcode prs_err;

13
kernel/cgroup/cpuset.c
View File

@@ -288,6 +288,7 @@ struct cpuset top_cpuset = {
.flags = BIT(CS_CPU_EXCLUSIVE) |
BIT(CS_MEM_EXCLUSIVE) | BIT(CS_SCHED_LOAD_BALANCE),
.partition_root_state = PRS_ROOT,
.dl_bw_cpu = -1,
};
/**
@@ -579,6 +580,8 @@ static struct cpuset *dup_or_alloc_cpuset(struct cpuset *cs)
if (!trial)
return NULL;
trial->dl_bw_cpu = -1;
/* Setup cpumask pointer array */
cpumask_var_t *pmask[4] = {
&trial->cpus_allowed,
@@ -2980,6 +2983,7 @@ static void reset_migrate_dl_data(struct cpuset *cs)
{
cs->nr_migrate_dl_tasks = 0;
cs->sum_migrate_dl_bw = 0;
cs->dl_bw_cpu = -1;
}
/* Called by cgroups to determine if a cpuset is usable; cpuset_mutex held */
@@ -3056,6 +3060,8 @@ static int cpuset_can_attach(struct cgroup_taskset *tset)
reset_migrate_dl_data(cs);
goto out_unlock;
}
cs->dl_bw_cpu = cpu;
}
out_success:
@@ -3080,12 +3086,11 @@ static void cpuset_cancel_attach(struct cgroup_taskset *tset)
mutex_lock(&cpuset_mutex);
dec_attach_in_progress_locked(cs);
if (cs->nr_migrate_dl_tasks) {
int cpu = cpumask_any(cs->effective_cpus);
if (cs->dl_bw_cpu >= 0)
dl_bw_free(cs->dl_bw_cpu, cs->sum_migrate_dl_bw);
dl_bw_free(cpu, cs->sum_migrate_dl_bw);
if (cs->nr_migrate_dl_tasks)
reset_migrate_dl_data(cs);
}
mutex_unlock(&cpuset_mutex);
}