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Message-ID: <2026011153--3a3b@gregkh>
Date: Sun, 11 Jan 2026 15:32:53 +0100
From: Greg Kroah-Hartman <gregkh@...uxfoundation.org>
To: linux-kernel@...r.kernel.org,
akpm@...ux-foundation.org,
torvalds@...ux-foundation.org,
stable@...r.kernel.org
Cc: lwn@....net,
jslaby@...e.cz,
Greg Kroah-Hartman <gregkh@...uxfoundation.org>
Subject: Re: Linux 6.18.5
diff --git a/Makefile b/Makefile
index 7b431af09b32..30c332829b0f 100644
--- a/Makefile
+++ b/Makefile
@@ -1,7 +1,7 @@
# SPDX-License-Identifier: GPL-2.0
VERSION = 6
PATCHLEVEL = 18
-SUBLEVEL = 4
+SUBLEVEL = 5
EXTRAVERSION =
NAME = Baby Opossum Posse
diff --git a/fs/nfs/localio.c b/fs/nfs/localio.c
index b98bb292fef0..ed2a7efaf8f2 100644
--- a/fs/nfs/localio.c
+++ b/fs/nfs/localio.c
@@ -623,8 +623,6 @@ static void nfs_local_call_read(struct work_struct *work)
ssize_t status;
int n_iters;
- save_cred = override_creds(filp->f_cred);
-
n_iters = atomic_read(&iocb->n_iters);
for (int i = 0; i < n_iters ; i++) {
if (iocb->iter_is_dio_aligned[i]) {
@@ -637,7 +635,10 @@ static void nfs_local_call_read(struct work_struct *work)
} else
iocb->kiocb.ki_flags &= ~IOCB_DIRECT;
+ save_cred = override_creds(filp->f_cred);
status = filp->f_op->read_iter(&iocb->kiocb, &iocb->iters[i]);
+ revert_creds(save_cred);
+
if (status != -EIOCBQUEUED) {
if (unlikely(status >= 0 && status < iocb->iters[i].count))
force_done = true; /* Partial read */
@@ -647,8 +648,6 @@ static void nfs_local_call_read(struct work_struct *work)
}
}
}
-
- revert_creds(save_cred);
}
static int
@@ -830,7 +829,6 @@ static void nfs_local_call_write(struct work_struct *work)
int n_iters;
current->flags |= PF_LOCAL_THROTTLE | PF_MEMALLOC_NOIO;
- save_cred = override_creds(filp->f_cred);
file_start_write(filp);
n_iters = atomic_read(&iocb->n_iters);
@@ -845,7 +843,10 @@ static void nfs_local_call_write(struct work_struct *work)
} else
iocb->kiocb.ki_flags &= ~IOCB_DIRECT;
+ save_cred = override_creds(filp->f_cred);
status = filp->f_op->write_iter(&iocb->kiocb, &iocb->iters[i]);
+ revert_creds(save_cred);
+
if (status != -EIOCBQUEUED) {
if (unlikely(status >= 0 && status < iocb->iters[i].count))
force_done = true; /* Partial write */
@@ -857,7 +858,6 @@ static void nfs_local_call_write(struct work_struct *work)
}
file_end_write(filp);
- revert_creds(save_cred);
current->flags = old_flags;
}
diff --git a/include/linux/sched/topology.h b/include/linux/sched/topology.h
index bbcfdf12aa6e..45c0022b91ce 100644
--- a/include/linux/sched/topology.h
+++ b/include/linux/sched/topology.h
@@ -92,6 +92,9 @@ struct sched_domain {
unsigned int nr_balance_failed; /* initialise to 0 */
/* idle_balance() stats */
+ unsigned int newidle_call;
+ unsigned int newidle_success;
+ unsigned int newidle_ratio;
u64 max_newidle_lb_cost;
unsigned long last_decay_max_lb_cost;
diff --git a/kernel/sched/core.c b/kernel/sched/core.c
index f754a60de848..eb47d294e2c5 100644
--- a/kernel/sched/core.c
+++ b/kernel/sched/core.c
@@ -121,6 +121,7 @@ EXPORT_TRACEPOINT_SYMBOL_GPL(sched_update_nr_running_tp);
EXPORT_TRACEPOINT_SYMBOL_GPL(sched_compute_energy_tp);
DEFINE_PER_CPU_SHARED_ALIGNED(struct rq, runqueues);
+DEFINE_PER_CPU(struct rnd_state, sched_rnd_state);
#ifdef CONFIG_SCHED_PROXY_EXEC
DEFINE_STATIC_KEY_TRUE(__sched_proxy_exec);
@@ -8591,6 +8592,8 @@ void __init sched_init_smp(void)
{
sched_init_numa(NUMA_NO_NODE);
+ prandom_init_once(&sched_rnd_state);
+
/*
* There's no userspace yet to cause hotplug operations; hence all the
* CPU masks are stable and all blatant races in the below code cannot
diff --git a/kernel/sched/fair.c b/kernel/sched/fair.c
index bfce451f1210..d1206f81f8b2 100644
--- a/kernel/sched/fair.c
+++ b/kernel/sched/fair.c
@@ -12122,24 +12122,43 @@ void update_max_interval(void)
max_load_balance_interval = HZ*num_online_cpus()/10;
}
-static inline bool update_newidle_cost(struct sched_domain *sd, u64 cost)
+static inline void update_newidle_stats(struct sched_domain *sd, unsigned int success)
{
+ sd->newidle_call++;
+ sd->newidle_success += success;
+
+ if (sd->newidle_call >= 1024) {
+ sd->newidle_ratio = sd->newidle_success;
+ sd->newidle_call /= 2;
+ sd->newidle_success /= 2;
+ }
+}
+
+static inline bool
+update_newidle_cost(struct sched_domain *sd, u64 cost, unsigned int success)
+{
+ unsigned long next_decay = sd->last_decay_max_lb_cost + HZ;
+ unsigned long now = jiffies;
+
+ if (cost)
+ update_newidle_stats(sd, success);
+
if (cost > sd->max_newidle_lb_cost) {
/*
* Track max cost of a domain to make sure to not delay the
* next wakeup on the CPU.
*/
sd->max_newidle_lb_cost = cost;
- sd->last_decay_max_lb_cost = jiffies;
- } else if (time_after(jiffies, sd->last_decay_max_lb_cost + HZ)) {
+ sd->last_decay_max_lb_cost = now;
+
+ } else if (time_after(now, next_decay)) {
/*
* Decay the newidle max times by ~1% per second to ensure that
* it is not outdated and the current max cost is actually
* shorter.
*/
sd->max_newidle_lb_cost = (sd->max_newidle_lb_cost * 253) / 256;
- sd->last_decay_max_lb_cost = jiffies;
-
+ sd->last_decay_max_lb_cost = now;
return true;
}
@@ -12171,7 +12190,7 @@ static void sched_balance_domains(struct rq *rq, enum cpu_idle_type idle)
* Decay the newidle max times here because this is a regular
* visit to all the domains.
*/
- need_decay = update_newidle_cost(sd, 0);
+ need_decay = update_newidle_cost(sd, 0, 0);
max_cost += sd->max_newidle_lb_cost;
/*
@@ -12787,14 +12806,16 @@ static int sched_balance_newidle(struct rq *this_rq, struct rq_flags *rf)
rcu_read_lock();
sd = rcu_dereference_check_sched_domain(this_rq->sd);
+ if (!sd) {
+ rcu_read_unlock();
+ goto out;
+ }
if (!get_rd_overloaded(this_rq->rd) ||
- (sd && this_rq->avg_idle < sd->max_newidle_lb_cost)) {
+ this_rq->avg_idle < sd->max_newidle_lb_cost) {
- if (sd)
- update_next_balance(sd, &next_balance);
+ update_next_balance(sd, &next_balance);
rcu_read_unlock();
-
goto out;
}
rcu_read_unlock();
@@ -12814,6 +12835,22 @@ static int sched_balance_newidle(struct rq *this_rq, struct rq_flags *rf)
break;
if (sd->flags & SD_BALANCE_NEWIDLE) {
+ unsigned int weight = 1;
+
+ if (sched_feat(NI_RANDOM)) {
+ /*
+ * Throw a 1k sided dice; and only run
+ * newidle_balance according to the success
+ * rate.
+ */
+ u32 d1k = sched_rng() % 1024;
+ weight = 1 + sd->newidle_ratio;
+ if (d1k > weight) {
+ update_newidle_stats(sd, 0);
+ continue;
+ }
+ weight = (1024 + weight/2) / weight;
+ }
pulled_task = sched_balance_rq(this_cpu, this_rq,
sd, CPU_NEWLY_IDLE,
@@ -12821,10 +12858,14 @@ static int sched_balance_newidle(struct rq *this_rq, struct rq_flags *rf)
t1 = sched_clock_cpu(this_cpu);
domain_cost = t1 - t0;
- update_newidle_cost(sd, domain_cost);
-
curr_cost += domain_cost;
t0 = t1;
+
+ /*
+ * Track max cost of a domain to make sure to not delay the
+ * next wakeup on the CPU.
+ */
+ update_newidle_cost(sd, domain_cost, weight * !!pulled_task);
}
/*
diff --git a/kernel/sched/features.h b/kernel/sched/features.h
index 3c12d9f93331..136a6584be79 100644
--- a/kernel/sched/features.h
+++ b/kernel/sched/features.h
@@ -121,3 +121,8 @@ SCHED_FEAT(WA_BIAS, true)
SCHED_FEAT(UTIL_EST, true)
SCHED_FEAT(LATENCY_WARN, false)
+
+/*
+ * Do newidle balancing proportional to its success rate using randomization.
+ */
+SCHED_FEAT(NI_RANDOM, true)
diff --git a/kernel/sched/sched.h b/kernel/sched/sched.h
index 92ec751799f5..2f8b06b12a98 100644
--- a/kernel/sched/sched.h
+++ b/kernel/sched/sched.h
@@ -5,6 +5,7 @@
#ifndef _KERNEL_SCHED_SCHED_H
#define _KERNEL_SCHED_SCHED_H
+#include <linux/prandom.h>
#include <linux/sched/affinity.h>
#include <linux/sched/autogroup.h>
#include <linux/sched/cpufreq.h>
@@ -1349,6 +1350,12 @@ static inline bool is_migration_disabled(struct task_struct *p)
}
DECLARE_PER_CPU_SHARED_ALIGNED(struct rq, runqueues);
+DECLARE_PER_CPU(struct rnd_state, sched_rnd_state);
+
+static inline u32 sched_rng(void)
+{
+ return prandom_u32_state(this_cpu_ptr(&sched_rnd_state));
+}
#define cpu_rq(cpu) (&per_cpu(runqueues, (cpu)))
#define this_rq() this_cpu_ptr(&runqueues)
diff --git a/kernel/sched/topology.c b/kernel/sched/topology.c
index 444bdfdab731..c7a4d2fff571 100644
--- a/kernel/sched/topology.c
+++ b/kernel/sched/topology.c
@@ -1662,6 +1662,12 @@ sd_init(struct sched_domain_topology_level *tl,
.last_balance = jiffies,
.balance_interval = sd_weight,
+
+ /* 50% success rate */
+ .newidle_call = 512,
+ .newidle_success = 256,
+ .newidle_ratio = 512,
+
.max_newidle_lb_cost = 0,
.last_decay_max_lb_cost = jiffies,
.child = child,
diff --git a/net/mptcp/protocol.c b/net/mptcp/protocol.c
index 221a5ea019e6..d4e3111ba643 100644
--- a/net/mptcp/protocol.c
+++ b/net/mptcp/protocol.c
@@ -2421,10 +2421,10 @@ bool __mptcp_retransmit_pending_data(struct sock *sk)
*/
static void __mptcp_subflow_disconnect(struct sock *ssk,
struct mptcp_subflow_context *subflow,
- unsigned int flags)
+ bool fastclosing)
{
if (((1 << ssk->sk_state) & (TCPF_CLOSE | TCPF_LISTEN)) ||
- subflow->send_fastclose) {
+ fastclosing) {
/* The MPTCP code never wait on the subflow sockets, TCP-level
* disconnect should never fail
*/
@@ -2476,7 +2476,7 @@ static void __mptcp_close_ssk(struct sock *sk, struct sock *ssk,
need_push = (flags & MPTCP_CF_PUSH) && __mptcp_retransmit_pending_data(sk);
if (!dispose_it) {
- __mptcp_subflow_disconnect(ssk, subflow, flags);
+ __mptcp_subflow_disconnect(ssk, subflow, msk->fastclosing);
release_sock(ssk);
goto out;
@@ -2789,6 +2789,7 @@ static void mptcp_do_fastclose(struct sock *sk)
struct mptcp_sock *msk = mptcp_sk(sk);
mptcp_set_state(sk, TCP_CLOSE);
+ msk->fastclosing = 1;
/* Explicitly send the fastclose reset as need */
if (__mptcp_check_fallback(msk))
@@ -3299,6 +3300,7 @@ static int mptcp_disconnect(struct sock *sk, int flags)
msk->bytes_sent = 0;
msk->bytes_retrans = 0;
msk->rcvspace_init = 0;
+ msk->fastclosing = 0;
WRITE_ONCE(sk->sk_shutdown, 0);
sk_error_report(sk);
diff --git a/net/mptcp/protocol.h b/net/mptcp/protocol.h
index 0e8b0a650108..30d5e5719793 100644
--- a/net/mptcp/protocol.h
+++ b/net/mptcp/protocol.h
@@ -321,7 +321,8 @@ struct mptcp_sock {
fastopening:1,
in_accept_queue:1,
free_first:1,
- rcvspace_init:1;
+ rcvspace_init:1,
+ fastclosing:1;
u32 notsent_lowat;
int keepalive_cnt;
int keepalive_idle;
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