Commit 41d701dd authored by Guopeng Zhang's avatar Guopeng Zhang Committed by Tejun Heo
Browse files

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



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: 2ef269ef ("cgroup/cpuset: Free DL BW in case can_attach() fails")
Signed-off-by: default avatarGuopeng Zhang <zhangguopeng@kylinos.cn>
Reviewed-by: default avatarWaiman Long <longman@redhat.com>
Signed-off-by: default avatarTejun Heo <tj@kernel.org>
parent c802f460

kernel/cgroup/cpuset-internal.h

+5 −0
Original line number Diff line number Diff line
@@ -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;

kernel/cgroup/cpuset.c

+9 −4
Original line number Diff line number Diff line
@@ -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);

}