From: Maurizio Lombardi mlombard@redhat.com
commit e45cc288724f0cfd497bb5920bcfa60caa335729 upstream.
Commit 5a836bf6b09f ("mm: slub: move flush_cpu_slab() invocations __free_slab() invocations out of IRQ context") moved all flush_cpu_slab() invocations to the global workqueue to avoid a problem related with deactivate_slab()/__free_slab() being called from an IRQ context on PREEMPT_RT kernels.
When the flush_all_cpu_locked() function is called from a task context it may happen that a workqueue with WQ_MEM_RECLAIM bit set ends up flushing the global workqueue, this will cause a dependency issue.
workqueue: WQ_MEM_RECLAIM nvme-delete-wq:nvme_delete_ctrl_work [nvme_core] is flushing !WQ_MEM_RECLAIM events:flush_cpu_slab WARNING: CPU: 37 PID: 410 at kernel/workqueue.c:2637 check_flush_dependency+0x10a/0x120 Workqueue: nvme-delete-wq nvme_delete_ctrl_work [nvme_core] RIP: 0010:check_flush_dependency+0x10a/0x120[ 453.262125] Call Trace: __flush_work.isra.0+0xbf/0x220 ? __queue_work+0x1dc/0x420 flush_all_cpus_locked+0xfb/0x120 __kmem_cache_shutdown+0x2b/0x320 kmem_cache_destroy+0x49/0x100 bioset_exit+0x143/0x190 blk_release_queue+0xb9/0x100 kobject_cleanup+0x37/0x130 nvme_fc_ctrl_free+0xc6/0x150 [nvme_fc] nvme_free_ctrl+0x1ac/0x2b0 [nvme_core]
Fix this bug by creating a workqueue for the flush operation with the WQ_MEM_RECLAIM bit set.
Fixes: 5a836bf6b09f ("mm: slub: move flush_cpu_slab() invocations __free_slab() invocations out of IRQ context") Cc: stable@vger.kernel.org Signed-off-by: Maurizio Lombardi mlombard@redhat.com Reviewed-by: Hyeonggon Yoo 42.hyeyoo@gmail.com Signed-off-by: Vlastimil Babka vbabka@suse.cz Signed-off-by: Greg Kroah-Hartman gregkh@linuxfoundation.org --- mm/slub.c | 9 ++++++++- 1 file changed, 8 insertions(+), 1 deletion(-)
--- a/mm/slub.c +++ b/mm/slub.c @@ -310,6 +310,11 @@ static inline void stat(const struct kme */ static nodemask_t slab_nodes;
+/* + * Workqueue used for flush_cpu_slab(). + */ +static struct workqueue_struct *flushwq; + /******************************************************************** * Core slab cache functions *******************************************************************/ @@ -2730,7 +2735,7 @@ static void flush_all_cpus_locked(struct INIT_WORK(&sfw->work, flush_cpu_slab); sfw->skip = false; sfw->s = s; - schedule_work_on(cpu, &sfw->work); + queue_work_on(cpu, flushwq, &sfw->work); }
for_each_online_cpu(cpu) { @@ -4880,6 +4885,8 @@ void __init kmem_cache_init(void)
void __init kmem_cache_init_late(void) { + flushwq = alloc_workqueue("slub_flushwq", WQ_MEM_RECLAIM, 0); + WARN_ON(!flushwq); }
struct kmem_cache *