| lists.openwall.net | lists / announce owl-users owl-dev john-users john-dev passwdqc-users yescrypt popa3d-users / oss-security kernel-hardening musl sabotage tlsify passwords / crypt-dev xvendor / Bugtraq Full-Disclosure linux-kernel linux-netdev linux-ext4 linux-hardening linux-cve-announce PHC | |
|
Open Source and information security mailing list archives
| ||
|
Message-ID: <20250904041516.3046-6-kprateek.nayak@amd.com>
Date: Thu, 4 Sep 2025 04:15:01 +0000
From: K Prateek Nayak <kprateek.nayak@....com>
To: Ingo Molnar <mingo@...hat.com>, Peter Zijlstra <peterz@...radead.org>,
Juri Lelli <juri.lelli@...hat.com>, Vincent Guittot
<vincent.guittot@...aro.org>, Anna-Maria Behnsen <anna-maria@...utronix.de>,
Frederic Weisbecker <frederic@...nel.org>, Thomas Gleixner
<tglx@...utronix.de>, <linux-kernel@...r.kernel.org>
CC: Dietmar Eggemann <dietmar.eggemann@....com>, Steven Rostedt
<rostedt@...dmis.org>, Ben Segall <bsegall@...gle.com>, Mel Gorman
<mgorman@...e.de>, Valentin Schneider <vschneid@...hat.com>, K Prateek Nayak
<kprateek.nayak@....com>, "Gautham R. Shenoy" <gautham.shenoy@....com>,
Swapnil Sapkal <swapnil.sapkal@....com>
Subject: [RFC PATCH 05/19] sched/topology: Attach new hierarchy in rq_attach_root()
Gregory Haskins introduced the concept of root domain in commit
57d885fea0da ("sched: add sched-domain roots") which put
rq_attach_root() before rcu_assign_pointer(rq->sd, sd).
Further development around dynamic sched domain allocation, and
update_top_cache_domain() that came later relied on the new sched
domain hierarchy and was naturaturally done after rq->sd was updated.
Since subsequent changes around nohz idle CPU tracking creates a
dependency for the fair_sched_class->offline() callback to use the old
hierarchy and the fair_sched_class->online() callback to use the
updated hierarchy, update rq->sd and the top cache domains within
rq_attach_root() between the two callbacks.
This modifies the flow as follows:
old flow new flow
======== ========
rq_attach_root() rq_attach_root()
set_rq_offline(); set_rq_offline(); /* Operate on old sd_llc */
set_rq_online(); rq->sd = sd;
rq->sd = sd; update_top_cache_domain()
update_top_cache_domain() set_rq_online(); /* Operate on new sd_llc */
No functional changes intended.
Signed-off-by: K Prateek Nayak <kprateek.nayak@....com>
---
kernel/sched/core.c | 2 +-
kernel/sched/sched.h | 2 +-
kernel/sched/topology.c | 38 ++++++++++++++++++++++++--------------
3 files changed, 26 insertions(+), 16 deletions(-)
diff --git a/kernel/sched/core.c b/kernel/sched/core.c
index feb750aae71b..771fc6239386 100644
--- a/kernel/sched/core.c
+++ b/kernel/sched/core.c
@@ -8798,7 +8798,7 @@ void __init sched_init(void)
INIT_LIST_HEAD(&rq->cfs_tasks);
- rq_attach_root(rq, &def_root_domain);
+ rq_attach_root(rq, &def_root_domain, NULL);
#ifdef CONFIG_NO_HZ_COMMON
rq->last_blocked_load_update_tick = jiffies;
atomic_set(&rq->nohz_flags, 0);
diff --git a/kernel/sched/sched.h b/kernel/sched/sched.h
index b5367c514c14..9ae3e2993641 100644
--- a/kernel/sched/sched.h
+++ b/kernel/sched/sched.h
@@ -1020,7 +1020,7 @@ struct root_domain {
extern void init_defrootdomain(void);
extern int sched_init_domains(const struct cpumask *cpu_map);
-extern void rq_attach_root(struct rq *rq, struct root_domain *rd);
+extern void rq_attach_root(struct rq *rq, struct root_domain *rd, struct sched_domain *sd);
extern void sched_get_rd(struct root_domain *rd);
extern void sched_put_rd(struct root_domain *rd);
diff --git a/kernel/sched/topology.c b/kernel/sched/topology.c
index f3ebb9e8fe00..a059641e12e5 100644
--- a/kernel/sched/topology.c
+++ b/kernel/sched/topology.c
@@ -469,9 +469,12 @@ static void free_rootdomain(struct rcu_head *rcu)
kfree(rd);
}
-void rq_attach_root(struct rq *rq, struct root_domain *rd)
+static void update_top_cache_domain(int cpu);
+
+void rq_attach_root(struct rq *rq, struct root_domain *rd, struct sched_domain *sd)
{
struct root_domain *old_rd = NULL;
+ int cpu = cpu_of(rq);
struct rq_flags rf;
rq_lock_irqsave(rq, &rf);
@@ -494,6 +497,8 @@ void rq_attach_root(struct rq *rq, struct root_domain *rd)
}
atomic_inc(&rd->refcount);
+ rcu_assign_pointer(rq->sd, sd);
+ update_top_cache_domain(cpu);
rq->rd = rd;
cpumask_set_cpu(rq->cpu, rd->span);
@@ -711,16 +716,27 @@ static void update_top_cache_domain(int cpu)
rcu_assign_pointer(per_cpu(sd_asym_cpucapacity, cpu), sd);
}
+struct s_data {
+ struct sched_domain_shared * __percpu *sds;
+ struct sched_domain * __percpu *sd;
+ struct root_domain *rd;
+};
+
/*
* Attach the domain 'sd' to 'cpu' as its base domain. Callers must
* hold the hotplug lock.
*/
static void
-cpu_attach_domain(struct sched_domain *sd, struct root_domain *rd, int cpu)
+cpu_attach_domain(struct s_data *d, int cpu)
{
+ struct root_domain *rd = d->rd;
+ struct sched_domain *sd = NULL;
struct rq *rq = cpu_rq(cpu);
struct sched_domain *tmp;
+ if (d->sd)
+ sd = *per_cpu_ptr(d->sd, cpu);
+
/* Remove the sched domains which do not contribute to scheduling. */
for (tmp = sd; tmp; ) {
struct sched_domain *parent = tmp->parent;
@@ -776,21 +792,13 @@ cpu_attach_domain(struct sched_domain *sd, struct root_domain *rd, int cpu)
sched_domain_debug(sd, cpu);
- rq_attach_root(rq, rd);
tmp = rq->sd;
- rcu_assign_pointer(rq->sd, sd);
+ rq_attach_root(rq, rd, sd);
dirty_sched_domain_sysctl(cpu);
destroy_sched_domains(tmp);
- update_top_cache_domain(cpu);
}
-struct s_data {
- struct sched_domain_shared * __percpu *sds;
- struct sched_domain * __percpu *sd;
- struct root_domain *rd;
-};
-
enum s_alloc {
sa_rootdomain,
sa_sd,
@@ -2642,9 +2650,8 @@ build_sched_domains(const struct cpumask *cpu_map, struct sched_domain_attr *att
rcu_read_lock();
for_each_cpu(i, cpu_map) {
rq = cpu_rq(i);
- sd = *per_cpu_ptr(d.sd, i);
- cpu_attach_domain(sd, d.rd, i);
+ cpu_attach_domain(&d, i);
if (lowest_flag_domain(i, SD_CLUSTER))
has_cluster = true;
@@ -2749,6 +2756,9 @@ int __init sched_init_domains(const struct cpumask *cpu_map)
static void detach_destroy_domains(const struct cpumask *cpu_map)
{
unsigned int cpu = cpumask_any(cpu_map);
+ struct s_data d = {
+ .rd = &def_root_domain,
+ };
int i;
if (rcu_access_pointer(per_cpu(sd_asym_cpucapacity, cpu)))
@@ -2759,7 +2769,7 @@ static void detach_destroy_domains(const struct cpumask *cpu_map)
rcu_read_lock();
for_each_cpu(i, cpu_map)
- cpu_attach_domain(NULL, &def_root_domain, i);
+ cpu_attach_domain(&d, i);
rcu_read_unlock();
}
--
2.34.1
Powered by blists - more mailing lists