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cpuset: Convert callback_lock to raw_spinlock_t
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The two commits below add up to a cpuset might_sleep() splat for RT:

8447a0f cpuset: convert callback_mutex to a spinlock
344736f cpuset: simplify cpuset_node_allowed API

BUG: sleeping function called from invalid context at kernel/locking/rtmutex.c:995
in_atomic(): 0, irqs_disabled(): 1, pid: 11718, name: cset
CPU: 135 PID: 11718 Comm: cset Tainted: G            E   4.10.0-rt1-rt #4
Hardware name: Intel Corporation BRICKLAND/BRICKLAND, BIOS BRHSXSD1.86B.0056.R01.1409242327 09/24/2014
Call Trace:
 ? dump_stack+0x5c/0x81
 ? ___might_sleep+0xf4/0x170
 ? rt_spin_lock+0x1c/0x50
 ? __cpuset_node_allowed+0x66/0xc0
 ? ___slab_alloc+0x390/0x570 <disables IRQs>
 ? anon_vma_fork+0x8f/0x140
 ? copy_page_range+0x6cf/0xb00
 ? anon_vma_fork+0x8f/0x140
 ? __slab_alloc.isra.74+0x5a/0x81
 ? anon_vma_fork+0x8f/0x140
 ? kmem_cache_alloc+0x1b5/0x1f0
 ? anon_vma_fork+0x8f/0x140
 ? copy_process.part.35+0x1670/0x1ee0
 ? _do_fork+0xdd/0x3f0
 ? _do_fork+0xdd/0x3f0
 ? do_syscall_64+0x61/0x170
 ? entry_SYSCALL64_slow_path+0x25/0x25

The later ensured that a NUMA box WILL take callback_lock in atomic
context by removing the allocator and reclaim path __GFP_HARDWALL
usage which prevented such contexts from taking callback_mutex.

One option would be to reinstate __GFP_HARDWALL protections for
RT, however, as the 8447a0f changelog states:

The callback_mutex is only used to synchronize reads/updates of cpusets'
flags and cpu/node masks. These operations should always proceed fast so
there's no reason why we can't use a spinlock instead of the mutex.

Cc: stable-rt@vger.kernel.org
Signed-off-by: Mike Galbraith <efault@gmx.de>
Signed-off-by: Sebastian Andrzej Siewior <bigeasy@linutronix.de>
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Mike Galbraith authored and Sebastian Andrzej Siewior committed Oct 28, 2020
1 parent 3327ab1 commit e3f4ff4
Showing 1 changed file with 35 additions and 35 deletions.
70 changes: 35 additions & 35 deletions kernel/cgroup/cpuset.c
View file
Original file line number Diff line number Diff line change
Expand Up @@ -345,7 +345,7 @@ void cpuset_read_unlock(void)
percpu_up_read(&cpuset_rwsem);
}

static DEFINE_SPINLOCK(callback_lock);
static DEFINE_RAW_SPINLOCK(callback_lock);

static struct workqueue_struct *cpuset_migrate_mm_wq;

Expand Down Expand Up @@ -1257,7 +1257,7 @@ static int update_parent_subparts_cpumask(struct cpuset *cpuset, int cmd,
* Newly added CPUs will be removed from effective_cpus and
* newly deleted ones will be added back to effective_cpus.
*/
spin_lock_irq(&callback_lock);
raw_spin_lock_irq(&callback_lock);
if (adding) {
cpumask_or(parent->subparts_cpus,
parent->subparts_cpus, tmp->addmask);
Expand All @@ -1276,7 +1276,7 @@ static int update_parent_subparts_cpumask(struct cpuset *cpuset, int cmd,
}

parent->nr_subparts_cpus = cpumask_weight(parent->subparts_cpus);
spin_unlock_irq(&callback_lock);
raw_spin_unlock_irq(&callback_lock);

return cmd == partcmd_update;
}
Expand Down Expand Up @@ -1381,7 +1381,7 @@ static void update_cpumasks_hier(struct cpuset *cs, struct tmpmasks *tmp)
continue;
rcu_read_unlock();

spin_lock_irq(&callback_lock);
raw_spin_lock_irq(&callback_lock);

cpumask_copy(cp->effective_cpus, tmp->new_cpus);
if (cp->nr_subparts_cpus &&
Expand Down Expand Up @@ -1412,7 +1412,7 @@ static void update_cpumasks_hier(struct cpuset *cs, struct tmpmasks *tmp)
= cpumask_weight(cp->subparts_cpus);
}
}
spin_unlock_irq(&callback_lock);
raw_spin_unlock_irq(&callback_lock);

WARN_ON(!is_in_v2_mode() &&
!cpumask_equal(cp->cpus_allowed, cp->effective_cpus));
Expand Down Expand Up @@ -1530,7 +1530,7 @@ static int update_cpumask(struct cpuset *cs, struct cpuset *trialcs,
return -EINVAL;
}

spin_lock_irq(&callback_lock);
raw_spin_lock_irq(&callback_lock);
cpumask_copy(cs->cpus_allowed, trialcs->cpus_allowed);

/*
Expand All @@ -1541,7 +1541,7 @@ static int update_cpumask(struct cpuset *cs, struct cpuset *trialcs,
cs->cpus_allowed);
cs->nr_subparts_cpus = cpumask_weight(cs->subparts_cpus);
}
spin_unlock_irq(&callback_lock);
raw_spin_unlock_irq(&callback_lock);

update_cpumasks_hier(cs, &tmp);

Expand Down Expand Up @@ -1735,9 +1735,9 @@ static void update_nodemasks_hier(struct cpuset *cs, nodemask_t *new_mems)
continue;
rcu_read_unlock();

spin_lock_irq(&callback_lock);
raw_spin_lock_irq(&callback_lock);
cp->effective_mems = *new_mems;
spin_unlock_irq(&callback_lock);
raw_spin_unlock_irq(&callback_lock);

WARN_ON(!is_in_v2_mode() &&
!nodes_equal(cp->mems_allowed, cp->effective_mems));
Expand Down Expand Up @@ -1805,9 +1805,9 @@ static int update_nodemask(struct cpuset *cs, struct cpuset *trialcs,
if (retval < 0)
goto done;

spin_lock_irq(&callback_lock);
raw_spin_lock_irq(&callback_lock);
cs->mems_allowed = trialcs->mems_allowed;
spin_unlock_irq(&callback_lock);
raw_spin_unlock_irq(&callback_lock);

/* use trialcs->mems_allowed as a temp variable */
update_nodemasks_hier(cs, &trialcs->mems_allowed);
Expand Down Expand Up @@ -1898,9 +1898,9 @@ static int update_flag(cpuset_flagbits_t bit, struct cpuset *cs,
spread_flag_changed = ((is_spread_slab(cs) != is_spread_slab(trialcs))
|| (is_spread_page(cs) != is_spread_page(trialcs)));

spin_lock_irq(&callback_lock);
raw_spin_lock_irq(&callback_lock);
cs->flags = trialcs->flags;
spin_unlock_irq(&callback_lock);
raw_spin_unlock_irq(&callback_lock);

if (!cpumask_empty(trialcs->cpus_allowed) && balance_flag_changed)
rebuild_sched_domains_locked();
Expand Down Expand Up @@ -2409,7 +2409,7 @@ static int cpuset_common_seq_show(struct seq_file *sf, void *v)
cpuset_filetype_t type = seq_cft(sf)->private;
int ret = 0;

spin_lock_irq(&callback_lock);
raw_spin_lock_irq(&callback_lock);

switch (type) {
case FILE_CPULIST:
Expand All @@ -2431,7 +2431,7 @@ static int cpuset_common_seq_show(struct seq_file *sf, void *v)
ret = -EINVAL;
}

spin_unlock_irq(&callback_lock);
raw_spin_unlock_irq(&callback_lock);
return ret;
}

Expand Down Expand Up @@ -2744,14 +2744,14 @@ static int cpuset_css_online(struct cgroup_subsys_state *css)

cpuset_inc();

spin_lock_irq(&callback_lock);
raw_spin_lock_irq(&callback_lock);
if (is_in_v2_mode()) {
cpumask_copy(cs->effective_cpus, parent->effective_cpus);
cs->effective_mems = parent->effective_mems;
cs->use_parent_ecpus = true;
parent->child_ecpus_count++;
}
spin_unlock_irq(&callback_lock);
raw_spin_unlock_irq(&callback_lock);

if (!test_bit(CGRP_CPUSET_CLONE_CHILDREN, &css->cgroup->flags))
goto out_unlock;
Expand All @@ -2778,12 +2778,12 @@ static int cpuset_css_online(struct cgroup_subsys_state *css)
}
rcu_read_unlock();

spin_lock_irq(&callback_lock);
raw_spin_lock_irq(&callback_lock);
cs->mems_allowed = parent->mems_allowed;
cs->effective_mems = parent->mems_allowed;
cpumask_copy(cs->cpus_allowed, parent->cpus_allowed);
cpumask_copy(cs->effective_cpus, parent->cpus_allowed);
spin_unlock_irq(&callback_lock);
raw_spin_unlock_irq(&callback_lock);
out_unlock:
percpu_up_write(&cpuset_rwsem);
put_online_cpus();
Expand Down Expand Up @@ -2839,7 +2839,7 @@ static void cpuset_css_free(struct cgroup_subsys_state *css)
static void cpuset_bind(struct cgroup_subsys_state *root_css)
{
percpu_down_write(&cpuset_rwsem);
spin_lock_irq(&callback_lock);
raw_spin_lock_irq(&callback_lock);

if (is_in_v2_mode()) {
cpumask_copy(top_cpuset.cpus_allowed, cpu_possible_mask);
Expand All @@ -2850,7 +2850,7 @@ static void cpuset_bind(struct cgroup_subsys_state *root_css)
top_cpuset.mems_allowed = top_cpuset.effective_mems;
}

spin_unlock_irq(&callback_lock);
raw_spin_unlock_irq(&callback_lock);
percpu_up_write(&cpuset_rwsem);
}

Expand Down Expand Up @@ -2947,12 +2947,12 @@ hotplug_update_tasks_legacy(struct cpuset *cs,
{
bool is_empty;

spin_lock_irq(&callback_lock);
raw_spin_lock_irq(&callback_lock);
cpumask_copy(cs->cpus_allowed, new_cpus);
cpumask_copy(cs->effective_cpus, new_cpus);
cs->mems_allowed = *new_mems;
cs->effective_mems = *new_mems;
spin_unlock_irq(&callback_lock);
raw_spin_unlock_irq(&callback_lock);

/*
* Don't call update_tasks_cpumask() if the cpuset becomes empty,
Expand Down Expand Up @@ -2989,10 +2989,10 @@ hotplug_update_tasks(struct cpuset *cs,
if (nodes_empty(*new_mems))
*new_mems = parent_cs(cs)->effective_mems;

spin_lock_irq(&callback_lock);
raw_spin_lock_irq(&callback_lock);
cpumask_copy(cs->effective_cpus, new_cpus);
cs->effective_mems = *new_mems;
spin_unlock_irq(&callback_lock);
raw_spin_unlock_irq(&callback_lock);

if (cpus_updated)
update_tasks_cpumask(cs);
Expand Down Expand Up @@ -3147,7 +3147,7 @@ static void cpuset_hotplug_workfn(struct work_struct *work)

/* synchronize cpus_allowed to cpu_active_mask */
if (cpus_updated) {
spin_lock_irq(&callback_lock);
raw_spin_lock_irq(&callback_lock);
if (!on_dfl)
cpumask_copy(top_cpuset.cpus_allowed, &new_cpus);
/*
Expand All @@ -3167,17 +3167,17 @@ static void cpuset_hotplug_workfn(struct work_struct *work)
}
}
cpumask_copy(top_cpuset.effective_cpus, &new_cpus);
spin_unlock_irq(&callback_lock);
raw_spin_unlock_irq(&callback_lock);
/* we don't mess with cpumasks of tasks in top_cpuset */
}

/* synchronize mems_allowed to N_MEMORY */
if (mems_updated) {
spin_lock_irq(&callback_lock);
raw_spin_lock_irq(&callback_lock);
if (!on_dfl)
top_cpuset.mems_allowed = new_mems;
top_cpuset.effective_mems = new_mems;
spin_unlock_irq(&callback_lock);
raw_spin_unlock_irq(&callback_lock);
update_tasks_nodemask(&top_cpuset);
}

Expand Down Expand Up @@ -3278,11 +3278,11 @@ void cpuset_cpus_allowed(struct task_struct *tsk, struct cpumask *pmask)
{
unsigned long flags;

spin_lock_irqsave(&callback_lock, flags);
raw_spin_lock_irqsave(&callback_lock, flags);
rcu_read_lock();
guarantee_online_cpus(task_cs(tsk), pmask);
rcu_read_unlock();
spin_unlock_irqrestore(&callback_lock, flags);
raw_spin_unlock_irqrestore(&callback_lock, flags);
}

/**
Expand Down Expand Up @@ -3343,11 +3343,11 @@ nodemask_t cpuset_mems_allowed(struct task_struct *tsk)
nodemask_t mask;
unsigned long flags;

spin_lock_irqsave(&callback_lock, flags);
raw_spin_lock_irqsave(&callback_lock, flags);
rcu_read_lock();
guarantee_online_mems(task_cs(tsk), &mask);
rcu_read_unlock();
spin_unlock_irqrestore(&callback_lock, flags);
raw_spin_unlock_irqrestore(&callback_lock, flags);

return mask;
}
Expand Down Expand Up @@ -3439,14 +3439,14 @@ bool __cpuset_node_allowed(int node, gfp_t gfp_mask)
return true;

/* Not hardwall and node outside mems_allowed: scan up cpusets */
spin_lock_irqsave(&callback_lock, flags);
raw_spin_lock_irqsave(&callback_lock, flags);

rcu_read_lock();
cs = nearest_hardwall_ancestor(task_cs(current));
allowed = node_isset(node, cs->mems_allowed);
rcu_read_unlock();

spin_unlock_irqrestore(&callback_lock, flags);
raw_spin_unlock_irqrestore(&callback_lock, flags);
return allowed;
}

Expand Down

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