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Message-ID: <172277654633.866296.14995229844387120847.tglx@xen13>
Date: Sun, 4 Aug 2024 15:02:57 +0200 (CEST)
From: Thomas Gleixner <tglx@...utronix.de>
To: Linus Torvalds <torvalds@...ux-foundation.org>
Cc: linux-kernel@...r.kernel.org, x86@...nel.org
Subject: [GIT pull] sched/urgent for v6.11-rc2
Linus,
please pull the latest sched/urgent branch from:
git://git.kernel.org/pub/scm/linux/kernel/git/tip/tip.git sched-urgent-2024-08-04
up to: fe7a11c78d2a: sched/core: Fix unbalance set_rq_online/offline() in sched_cpu_deactivate()
Scheduler fixes:
- When stime is larger than rtime due to accounting imprecision, then
utime = rtime - stime becomes negative. As this is unsigned math, the
result becomes a huge positive number. Cure it by resetting stime to
rtime in that case, so utime becomes 0.
- Restore consistent state when sched_cpu_deactivate() fails.
When offlining a CPU fails in sched_cpu_deactivate() after the SMT
present counter has been decremented, then the function aborts but
fails to increment the SMT present counter and leaves it imbalanced.
Consecutive operations cause it to underflow. Add the missing fixup
for the error path.
As SMT accounting the runqueue needs to marked online again in the
error exit path to restore consistent state.
Thanks,
tglx
------------------>
Yang Yingliang (4):
sched/smt: Introduce sched_smt_present_inc/dec() helper
sched/smt: Fix unbalance sched_smt_present dec/inc
sched/core: Introduce sched_set_rq_on/offline() helper
sched/core: Fix unbalance set_rq_online/offline() in sched_cpu_deactivate()
Zheng Zucheng (1):
sched/cputime: Fix mul_u64_u64_div_u64() precision for cputime
kernel/sched/core.c | 68 ++++++++++++++++++++++++++++++++++----------------
kernel/sched/cputime.c | 6 +++++
2 files changed, 53 insertions(+), 21 deletions(-)
diff --git a/kernel/sched/core.c b/kernel/sched/core.c
index a9f655025607..f3951e4a55e5 100644
--- a/kernel/sched/core.c
+++ b/kernel/sched/core.c
@@ -7845,6 +7845,30 @@ void set_rq_offline(struct rq *rq)
}
}
+static inline void sched_set_rq_online(struct rq *rq, int cpu)
+{
+ struct rq_flags rf;
+
+ rq_lock_irqsave(rq, &rf);
+ if (rq->rd) {
+ BUG_ON(!cpumask_test_cpu(cpu, rq->rd->span));
+ set_rq_online(rq);
+ }
+ rq_unlock_irqrestore(rq, &rf);
+}
+
+static inline void sched_set_rq_offline(struct rq *rq, int cpu)
+{
+ struct rq_flags rf;
+
+ rq_lock_irqsave(rq, &rf);
+ if (rq->rd) {
+ BUG_ON(!cpumask_test_cpu(cpu, rq->rd->span));
+ set_rq_offline(rq);
+ }
+ rq_unlock_irqrestore(rq, &rf);
+}
+
/*
* used to mark begin/end of suspend/resume:
*/
@@ -7895,10 +7919,25 @@ static int cpuset_cpu_inactive(unsigned int cpu)
return 0;
}
+static inline void sched_smt_present_inc(int cpu)
+{
+#ifdef CONFIG_SCHED_SMT
+ if (cpumask_weight(cpu_smt_mask(cpu)) == 2)
+ static_branch_inc_cpuslocked(&sched_smt_present);
+#endif
+}
+
+static inline void sched_smt_present_dec(int cpu)
+{
+#ifdef CONFIG_SCHED_SMT
+ if (cpumask_weight(cpu_smt_mask(cpu)) == 2)
+ static_branch_dec_cpuslocked(&sched_smt_present);
+#endif
+}
+
int sched_cpu_activate(unsigned int cpu)
{
struct rq *rq = cpu_rq(cpu);
- struct rq_flags rf;
/*
* Clear the balance_push callback and prepare to schedule
@@ -7906,13 +7945,10 @@ int sched_cpu_activate(unsigned int cpu)
*/
balance_push_set(cpu, false);
-#ifdef CONFIG_SCHED_SMT
/*
* When going up, increment the number of cores with SMT present.
*/
- if (cpumask_weight(cpu_smt_mask(cpu)) == 2)
- static_branch_inc_cpuslocked(&sched_smt_present);
-#endif
+ sched_smt_present_inc(cpu);
set_cpu_active(cpu, true);
if (sched_smp_initialized) {
@@ -7930,12 +7966,7 @@ int sched_cpu_activate(unsigned int cpu)
* 2) At runtime, if cpuset_cpu_active() fails to rebuild the
* domains.
*/
- rq_lock_irqsave(rq, &rf);
- if (rq->rd) {
- BUG_ON(!cpumask_test_cpu(cpu, rq->rd->span));
- set_rq_online(rq);
- }
- rq_unlock_irqrestore(rq, &rf);
+ sched_set_rq_online(rq, cpu);
return 0;
}
@@ -7943,7 +7974,6 @@ int sched_cpu_activate(unsigned int cpu)
int sched_cpu_deactivate(unsigned int cpu)
{
struct rq *rq = cpu_rq(cpu);
- struct rq_flags rf;
int ret;
/*
@@ -7974,20 +8004,14 @@ int sched_cpu_deactivate(unsigned int cpu)
*/
synchronize_rcu();
- rq_lock_irqsave(rq, &rf);
- if (rq->rd) {
- BUG_ON(!cpumask_test_cpu(cpu, rq->rd->span));
- set_rq_offline(rq);
- }
- rq_unlock_irqrestore(rq, &rf);
+ sched_set_rq_offline(rq, cpu);
-#ifdef CONFIG_SCHED_SMT
/*
* When going down, decrement the number of cores with SMT present.
*/
- if (cpumask_weight(cpu_smt_mask(cpu)) == 2)
- static_branch_dec_cpuslocked(&sched_smt_present);
+ sched_smt_present_dec(cpu);
+#ifdef CONFIG_SCHED_SMT
sched_core_cpu_deactivate(cpu);
#endif
@@ -7997,6 +8021,8 @@ int sched_cpu_deactivate(unsigned int cpu)
sched_update_numa(cpu, false);
ret = cpuset_cpu_inactive(cpu);
if (ret) {
+ sched_smt_present_inc(cpu);
+ sched_set_rq_online(rq, cpu);
balance_push_set(cpu, false);
set_cpu_active(cpu, true);
sched_update_numa(cpu, true);
diff --git a/kernel/sched/cputime.c b/kernel/sched/cputime.c
index a5e00293ae43..0bed0fa1acd9 100644
--- a/kernel/sched/cputime.c
+++ b/kernel/sched/cputime.c
@@ -582,6 +582,12 @@ void cputime_adjust(struct task_cputime *curr, struct prev_cputime *prev,
}
stime = mul_u64_u64_div_u64(stime, rtime, stime + utime);
+ /*
+ * Because mul_u64_u64_div_u64() can approximate on some
+ * achitectures; enforce the constraint that: a*b/(b+c) <= a.
+ */
+ if (unlikely(stime > rtime))
+ stime = rtime;
update:
/*
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