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workqueue: use RCU accessors when populating wq->cpu_pwq

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wq->cpu_pwq holds RCU-protected pwq pointers, but the percpu allocation
path fills it in with plain loads and stores, which sparse flags:

  kernel/workqueue.c:5682:57: sparse: incorrect type in initializer (different address spaces) @@     expected struct pool_workqueue **pwq_p @@     got struct pool_workqueue [noderef] __rcu ** @@

Allocate the array as __rcu pointers and publish each pwq with
rcu_assign_pointer() once it is initialized and linked, the order
install_unbound_pwq() uses.

The warnings are not new: commit 79f23600bc ("workqueue: factor out
get_percpu_pool()") only turned the flagged assignment into an
initializer.

Reported-by: kernel test robot <lkp@intel.com>
Closes: https://lore.kernel.org/oe-kbuild-all/202608120931.tvTzq1gD-lkp@intel.com/
Signed-off-by: Breno Leitao <leitao@debian.org>
Signed-off-by: Tejun Heo <tj@kernel.org>
This commit is contained in:
Breno Leitao 2026-08-12 09:03:19 -07:00 committed by Tejun Heo
parent 7aef540078
commit 1d125f0e6c
1 changed files with 12 additions and 7 deletions
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19
kernel/workqueue.c
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@ -5681,21 +5681,23 @@ static void unbound_wq_update_pwq(struct workqueue_struct *wq, int cpu)
static int alloc_and_link_percpu_pwqs(struct workqueue_struct *wq)
{
struct pool_workqueue *pwq;
int cpu;
for_each_possible_cpu(cpu) {
struct pool_workqueue **pwq_p = per_cpu_ptr(wq->cpu_pwq, cpu);
struct worker_pool *pool = get_percpu_pool(wq, cpu);
*pwq_p = kmem_cache_alloc_node(pwq_cache, GFP_KERNEL, pool->node);
if (!*pwq_p)
pwq = kmem_cache_alloc_node(pwq_cache, GFP_KERNEL, pool->node);
if (!pwq)
return -ENOMEM;
init_pwq(*pwq_p, wq, pool);
init_pwq(pwq, wq, pool);
mutex_lock(&wq->mutex);
link_pwq(*pwq_p);
link_pwq(pwq);
mutex_unlock(&wq->mutex);
rcu_assign_pointer(*per_cpu_ptr(wq->cpu_pwq, cpu), pwq);
}
return 0;
@ -5708,7 +5710,7 @@ static int alloc_and_link_pwqs(struct workqueue_struct *wq)
lockdep_assert_held(&wq_pool_mutex);
wq->cpu_pwq = alloc_percpu(struct pool_workqueue *);
wq->cpu_pwq = alloc_percpu(struct pool_workqueue __rcu *);
if (!wq->cpu_pwq)
goto enomem;
@ -5734,8 +5736,11 @@ static int alloc_and_link_pwqs(struct workqueue_struct *wq)
enomem:
if (wq->cpu_pwq) {
for_each_possible_cpu(cpu) {
struct pool_workqueue *pwq = *per_cpu_ptr(wq->cpu_pwq, cpu);
struct pool_workqueue __rcu **slot;
struct pool_workqueue *pwq;
slot = per_cpu_ptr(wq->cpu_pwq, cpu);
pwq = rcu_access_pointer(*slot);
if (pwq) {
/*
* Unlink pwq from wq->pwqs since link_pwq()