4.1.38-rt46-rc1 stable review patch.
If you have any objection to the inclusion of this patch, let me know.

--- 8< --- 8< --- 8< ---
From: Mike Galbraith <efa...@gmx.de>

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

8447a0fee974 cpuset: convert callback_mutex to a spinlock
344736f29b35 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 8447a0fee974 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...@vger.kernel.org
Signed-off-by: Mike Galbraith <efa...@gmx.de>
Signed-off-by: Sebastian Andrzej Siewior <bige...@linutronix.de>
(cherry picked from commit 5625380ec638bdc89813f0bac9d1e431514e8a19)
Signed-off-by: Julia Cartwright <ju...@ni.com>
---
 kernel/cpuset.c | 66 ++++++++++++++++++++++++++++-----------------------------
 1 file changed, 33 insertions(+), 33 deletions(-)

diff --git a/kernel/cpuset.c b/kernel/cpuset.c
index 71403502411b..45da566b9749 100644
--- a/kernel/cpuset.c
+++ b/kernel/cpuset.c
@@ -284,7 +284,7 @@ static struct cpuset top_cpuset = {
  */
 
 static DEFINE_MUTEX(cpuset_mutex);
-static DEFINE_SPINLOCK(callback_lock);
+static DEFINE_RAW_SPINLOCK(callback_lock);
 
 /*
  * CPU / memory hotplug is handled asynchronously.
@@ -903,9 +903,9 @@ static void update_cpumasks_hier(struct cpuset *cs, struct 
cpumask *new_cpus)
                        continue;
                rcu_read_unlock();
 
-               spin_lock_irq(&callback_lock);
+               raw_spin_lock_irq(&callback_lock);
                cpumask_copy(cp->effective_cpus, new_cpus);
-               spin_unlock_irq(&callback_lock);
+               raw_spin_unlock_irq(&callback_lock);
 
                WARN_ON(!cgroup_on_dfl(cp->css.cgroup) &&
                        !cpumask_equal(cp->cpus_allowed, cp->effective_cpus));
@@ -970,9 +970,9 @@ static int update_cpumask(struct cpuset *cs, struct cpuset 
*trialcs,
        if (retval < 0)
                return retval;
 
-       spin_lock_irq(&callback_lock);
+       raw_spin_lock_irq(&callback_lock);
        cpumask_copy(cs->cpus_allowed, trialcs->cpus_allowed);
-       spin_unlock_irq(&callback_lock);
+       raw_spin_unlock_irq(&callback_lock);
 
        /* use trialcs->cpus_allowed as a temp variable */
        update_cpumasks_hier(cs, trialcs->cpus_allowed);
@@ -1159,9 +1159,9 @@ 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(!cgroup_on_dfl(cp->css.cgroup) &&
                        !nodes_equal(cp->mems_allowed, cp->effective_mems));
@@ -1229,9 +1229,9 @@ 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);
@@ -1322,9 +1322,9 @@ 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();
@@ -1726,7 +1726,7 @@ 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:
@@ -1745,7 +1745,7 @@ 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;
 }
 
@@ -1962,12 +1962,12 @@ static int cpuset_css_online(struct cgroup_subsys_state 
*css)
 
        cpuset_inc();
 
-       spin_lock_irq(&callback_lock);
+       raw_spin_lock_irq(&callback_lock);
        if (cgroup_on_dfl(cs->css.cgroup)) {
                cpumask_copy(cs->effective_cpus, parent->effective_cpus);
                cs->effective_mems = parent->effective_mems;
        }
-       spin_unlock_irq(&callback_lock);
+       raw_spin_unlock_irq(&callback_lock);
 
        if (!test_bit(CGRP_CPUSET_CLONE_CHILDREN, &css->cgroup->flags))
                goto out_unlock;
@@ -1994,12 +1994,12 @@ 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:
        mutex_unlock(&cpuset_mutex);
        return 0;
@@ -2038,7 +2038,7 @@ static void cpuset_css_free(struct cgroup_subsys_state 
*css)
 static void cpuset_bind(struct cgroup_subsys_state *root_css)
 {
        mutex_lock(&cpuset_mutex);
-       spin_lock_irq(&callback_lock);
+       raw_spin_lock_irq(&callback_lock);
 
        if (cgroup_on_dfl(root_css->cgroup)) {
                cpumask_copy(top_cpuset.cpus_allowed, cpu_possible_mask);
@@ -2049,7 +2049,7 @@ 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);
        mutex_unlock(&cpuset_mutex);
 }
 
@@ -2149,12 +2149,12 @@ 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,
@@ -2191,10 +2191,10 @@ 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);
@@ -2280,21 +2280,21 @@ 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);
                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);
        }
 
@@ -2389,11 +2389,11 @@ 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);
 }
 
 void cpuset_cpus_allowed_fallback(struct task_struct *tsk)
@@ -2441,11 +2441,11 @@ 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;
 }
@@ -2537,14 +2537,14 @@ int __cpuset_node_allowed(int node, gfp_t gfp_mask)
                return 1;
 
        /* 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;
 }
 
-- 
2.11.1

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