[PATCH 1/2] cgroup/cpuset: Update stale generate_sched_domains() comments

[PATCH 1/2] cgroup/cpuset: Update stale generate_sched_domains() comments

[Juri Lelli]

Commit fc560a26acce ("cpuset: replace cpuset->stack_list with
cpuset_for_each_descendant_pre()") removed the local list (q)
that was used to perform a top-down scan of all cpusets;
however, comments mentioning it were not updated.

Update comments to reflect current implementation.

Signed-off-by: Juri Lelli <juri.lelli@redhat.com>
---
 kernel/cgroup/cpuset.c | 11 +++++------
 1 file changed, 5 insertions(+), 6 deletions(-)

diff --git a/kernel/cgroup/cpuset.c b/kernel/cgroup/cpuset.c
index f0decd8165e7..f0822a730879 100644
--- a/kernel/cgroup/cpuset.c
+++ b/kernel/cgroup/cpuset.c
@@ -725,11 +725,10 @@ static inline int nr_cpusets(void)
  * Must be called with cpuset_mutex held.
  *
  * The three key local variables below are:
- *    q  - a linked-list queue of cpuset pointers, used to implement a
- *	   top-down scan of all cpusets.  This scan loads a pointer
- *	   to each cpuset marked is_sched_load_balance into the
- *	   array 'csa'.  For our purposes, rebuilding the schedulers
- *	   sched domains, we can ignore !is_sched_load_balance cpusets.
+ *    cp - cpuset pointer, used (together with pos_css) to perform a
+ *	   top-down scan of all cpusets. For our purposes, rebuilding
+ *	   the schedulers sched domains, we can ignore !is_sched_load_
+ *	   balance cpusets.
  *  csa  - (for CpuSet Array) Array of pointers to all the cpusets
  *	   that need to be load balanced, for convenient iterative
  *	   access by the subsequent code that finds the best partition,
@@ -760,7 +759,7 @@ static inline int nr_cpusets(void)
 static int generate_sched_domains(cpumask_var_t **domains,
 			struct sched_domain_attr **attributes)
 {
-	struct cpuset *cp;	/* scans q */
+	struct cpuset *cp;	/* top-down scan of cpusets */
 	struct cpuset **csa;	/* array of all cpuset ptrs */
 	int csn;		/* how many cpuset ptrs in csa so far */
 	int i, j, k;		/* indices for partition finding loops */
-- 
2.17.2

[PATCH 2/2] sched/topology: Update init_sched_domains() comment

[Juri Lelli]

Holding hotplug lock is not a requirement anymore for callers of sched_
init_domains after commit 6acce3ef8452 ("sched: Remove get_online_cpus()
usage").

Update the relative comment preceding init_sched_domains().

Signed-off-by: Juri Lelli <juri.lelli@redhat.com>
---
 kernel/sched/topology.c | 5 ++---
 1 file changed, 2 insertions(+), 3 deletions(-)

diff --git a/kernel/sched/topology.c b/kernel/sched/topology.c
index 8d7f15ba5916..10e61b62f138 100644
--- a/kernel/sched/topology.c
+++ b/kernel/sched/topology.c
@@ -1850,9 +1850,8 @@ void free_sched_domains(cpumask_var_t doms[], unsigned int ndoms)
 }
 
 /*
- * Set up scheduler domains and groups. Callers must hold the hotplug lock.
- * For now this just excludes isolated CPUs, but could be used to
- * exclude other special cases in the future.
+ * Set up scheduler domains and groups.  For now this just excludes isolated
+ * CPUs, but could be used to exclude other special cases in the future.
  */
 int sched_init_domains(const struct cpumask *cpu_map)
 {
-- 
2.17.2

Re: [PATCH 1/2] cgroup/cpuset: Update stale generate_sched_domains() comments

[Tejun Heo]

On Wed, Dec 19, 2018 at 02:34:44PM +0100, Juri Lelli wrote:
> Commit fc560a26acce ("cpuset: replace cpuset->stack_list with
> cpuset_for_each_descendant_pre()") removed the local list (q)
> that was used to perform a top-down scan of all cpusets;
> however, comments mentioning it were not updated.
> 
> Update comments to reflect current implementation.
> 
> Signed-off-by: Juri Lelli <juri.lelli@redhat.com>

Acked-by: Tejun Heo <tj@kernel.org>

Prolly better to route through scheduler tree together with the second
patch?

Thanks.

-- 
tejun