From: Peter Zijlstra peterz@infradead.org
mainline inclusion from mainline-v5.14 commit 3c474b3239f12fe0b00d7e82481f36a1f31e79ab category: bugfix bugzilla: https://gitee.com/openeuler/kernel/issues/I5OOWG CVE: NA
Reference: https://git.kernel.org/pub/scm/linux/kernel/git/torvalds/linux.git/commit/?i...
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Eugene tripped over the case where rq_lock(), as called in a for_each_possible_cpu() loop came apart because rq->core hadn't been setup yet.
This is a somewhat unusual, but valid case.
Rework things such that rq->core is initialized to point at itself. IOW initialize each CPU as a single threaded Core. CPU online will then join the new CPU (thread) to an existing Core where needed.
For completeness sake, have CPU offline fully undo the state so as to not presume the topology will match the next time it comes online.
Fixes: 9edeaea1bc45 ("sched: Core-wide rq->lock") Reported-by: Eugene Syromiatnikov esyr@redhat.com Signed-off-by: Peter Zijlstra (Intel) peterz@infradead.org Reviewed-by: Josh Don joshdon@google.com Tested-by: Eugene Syromiatnikov esyr@redhat.com Link: https://lkml.kernel.org/r/YR473ZGeKqMs6kw+@hirez.programming.kicks-ass.net Conflicts: kernel/sched/core.c [Bugfix ed3cd45f8ca87("Merge tag 'v5.11' into sched/core, to pick up fixes & refresh the branch") is not applied.] Signed-off-by: Lin Shengwang linshengwang1@huawei.com Reviewed-by: lihua hucool.lihua@huawei.com Signed-off-by: Zheng Zengkai zhengzengkai@huawei.com --- kernel/sched/core.c | 143 +++++++++++++++++++++++++++++++++++-------- kernel/sched/sched.h | 2 +- 2 files changed, 118 insertions(+), 27 deletions(-)
diff --git a/kernel/sched/core.c b/kernel/sched/core.c index fb1195f295e1..4e82b38eb778 100644 --- a/kernel/sched/core.c +++ b/kernel/sched/core.c @@ -228,9 +228,30 @@ static DEFINE_MUTEX(sched_core_mutex); static atomic_t sched_core_count; static struct cpumask sched_core_mask;
+static void sched_core_lock(int cpu, unsigned long *flags) +{ + const struct cpumask *smt_mask = cpu_smt_mask(cpu); + int t, i = 0; + + local_irq_save(*flags); + for_each_cpu(t, smt_mask) + raw_spin_lock_nested(&cpu_rq(t)->__lock, i++); +} + +static void sched_core_unlock(int cpu, unsigned long *flags) +{ + const struct cpumask *smt_mask = cpu_smt_mask(cpu); + int t; + + for_each_cpu(t, smt_mask) + raw_spin_unlock(&cpu_rq(t)->__lock); + local_irq_restore(*flags); +} + static void __sched_core_flip(bool enabled) { - int cpu, t, i; + unsigned long flags; + int cpu, t;
cpus_read_lock();
@@ -241,19 +262,12 @@ static void __sched_core_flip(bool enabled) for_each_cpu(cpu, &sched_core_mask) { const struct cpumask *smt_mask = cpu_smt_mask(cpu);
- i = 0; - local_irq_disable(); - for_each_cpu(t, smt_mask) { - /* supports up to SMT8 */ - raw_spin_lock_nested(&cpu_rq(t)->__lock, i++); - } + sched_core_lock(cpu, &flags);
for_each_cpu(t, smt_mask) cpu_rq(t)->core_enabled = enabled;
- for_each_cpu(t, smt_mask) - raw_spin_unlock(&cpu_rq(t)->__lock); - local_irq_enable(); + sched_core_unlock(cpu, &flags);
cpumask_andnot(&sched_core_mask, &sched_core_mask, smt_mask); } @@ -5173,35 +5187,109 @@ void queue_core_balance(struct rq *rq) queue_balance_callback(rq, &per_cpu(core_balance_head, rq->cpu), sched_core_balance); }
-static inline void sched_core_cpu_starting(unsigned int cpu) +static void sched_core_cpu_starting(unsigned int cpu) { const struct cpumask *smt_mask = cpu_smt_mask(cpu); - struct rq *rq, *core_rq = NULL; - int i; + struct rq *rq = cpu_rq(cpu), *core_rq = NULL; + unsigned long flags; + int t;
- core_rq = cpu_rq(cpu)->core; + sched_core_lock(cpu, &flags);
- if (!core_rq) { - for_each_cpu(i, smt_mask) { - rq = cpu_rq(i); - if (rq->core && rq->core == rq) - core_rq = rq; + WARN_ON_ONCE(rq->core != rq); + + /* if we're the first, we'll be our own leader */ + if (cpumask_weight(smt_mask) == 1) + goto unlock; + + /* find the leader */ + for_each_cpu(t, smt_mask) { + if (t == cpu) + continue; + rq = cpu_rq(t); + if (rq->core == rq) { + core_rq = rq; + break; } + }
- if (!core_rq) - core_rq = cpu_rq(cpu); + if (WARN_ON_ONCE(!core_rq)) /* whoopsie */ + goto unlock;
- for_each_cpu(i, smt_mask) { - rq = cpu_rq(i); + /* install and validate core_rq */ + for_each_cpu(t, smt_mask) { + rq = cpu_rq(t);
- WARN_ON_ONCE(rq->core && rq->core != core_rq); + if (t == cpu) rq->core = core_rq; - } + + WARN_ON_ONCE(rq->core != core_rq); } + +unlock: + sched_core_unlock(cpu, &flags); } + +static void sched_core_cpu_deactivate(unsigned int cpu) +{ + const struct cpumask *smt_mask = cpu_smt_mask(cpu); + struct rq *rq = cpu_rq(cpu), *core_rq = NULL; + unsigned long flags; + int t; + + sched_core_lock(cpu, &flags); + + /* if we're the last man standing, nothing to do */ + if (cpumask_weight(smt_mask) == 1) { + WARN_ON_ONCE(rq->core != rq); + goto unlock; + } + + /* if we're not the leader, nothing to do */ + if (rq->core != rq) + goto unlock; + + /* find a new leader */ + for_each_cpu(t, smt_mask) { + if (t == cpu) + continue; + core_rq = cpu_rq(t); + break; + } + + if (WARN_ON_ONCE(!core_rq)) /* impossible */ + goto unlock; + + /* copy the shared state to the new leader */ + core_rq->core_task_seq = rq->core_task_seq; + core_rq->core_pick_seq = rq->core_pick_seq; + core_rq->core_cookie = rq->core_cookie; + core_rq->core_forceidle = rq->core_forceidle; + core_rq->core_forceidle_seq = rq->core_forceidle_seq; + + /* install new leader */ + for_each_cpu(t, smt_mask) { + rq = cpu_rq(t); + rq->core = core_rq; + } + +unlock: + sched_core_unlock(cpu, &flags); +} + +static inline void sched_core_cpu_dying(unsigned int cpu) +{ + struct rq *rq = cpu_rq(cpu); + + if (rq->core != rq) + rq->core = rq; +} + #else /* !CONFIG_SCHED_CORE */
static inline void sched_core_cpu_starting(unsigned int cpu) {} +static inline void sched_core_cpu_deactivate(unsigned int cpu) {} +static inline void sched_core_cpu_dying(unsigned int cpu) {}
static struct task_struct * pick_next_task(struct rq *rq, struct task_struct *prev, struct rq_flags *rf) @@ -7980,6 +8068,8 @@ int sched_cpu_deactivate(unsigned int cpu) */ if (cpumask_weight(cpu_smt_mask(cpu)) == 2) static_branch_dec_cpuslocked(&sched_smt_present); + + sched_core_cpu_deactivate(cpu); #endif
if (!sched_smp_initialized) @@ -8032,6 +8122,7 @@ int sched_cpu_dying(unsigned int cpu) update_max_interval(); nohz_balance_exit_idle(rq); hrtick_clear(rq); + sched_core_cpu_dying(cpu); return 0; } #endif @@ -8240,7 +8331,7 @@ void __init sched_init(void) atomic_set(&rq->nr_iowait, 0);
#ifdef CONFIG_SCHED_CORE - rq->core = NULL; + rq->core = rq; rq->core_pick = NULL; rq->core_enabled = 0; rq->core_tree = RB_ROOT; diff --git a/kernel/sched/sched.h b/kernel/sched/sched.h index 91f8795f0693..e317f02ce2e5 100644 --- a/kernel/sched/sched.h +++ b/kernel/sched/sched.h @@ -1120,7 +1120,7 @@ struct rq { unsigned int core_sched_seq; struct rb_root core_tree;
- /* shared state */ + /* shared state -- careful with sched_core_cpu_deactivate() */ unsigned int core_task_seq; unsigned int core_pick_seq; unsigned long core_cookie;