Hi. While running v5.10-rc5-rt11 I bumped into the following:
``` BUG: scheduling while atomic: git/18695/0x00000002 Preemption disabled at: [<ffffffffbb93fcb3>] z3fold_zpool_malloc+0x463/0x6e0 … Call Trace: dump_stack+0x6d/0x88 __schedule_bug.cold+0x88/0x96 __schedule+0x69e/0x8c0 preempt_schedule_lock+0x51/0x150 rt_spin_lock_slowlock_locked+0x117/0x2c0 rt_spin_lock_slowlock+0x58/0x80 rt_spin_lock+0x2a/0x40 z3fold_zpool_malloc+0x4c1/0x6e0 zswap_frontswap_store+0x39c/0x980 __frontswap_store+0x6e/0xf0 swap_writepage+0x39/0x70 shmem_writepage+0x31b/0x490 pageout+0xf4/0x350 shrink_page_list+0xa28/0xcc0 shrink_inactive_list+0x300/0x690 shrink_lruvec+0x59a/0x770 shrink_node+0x2d6/0x8d0 do_try_to_free_pages+0xda/0x530 try_to_free_pages+0xff/0x260 __alloc_pages_slowpath.constprop.0+0x3d5/0x1230 __alloc_pages_nodemask+0x2f6/0x350 allocate_slab+0x3da/0x660 ___slab_alloc+0x4ff/0x760 __slab_alloc.constprop.0+0x7a/0x100 kmem_cache_alloc+0x27b/0x2c0 __d_alloc+0x22/0x230 d_alloc_parallel+0x67/0x5e0 __lookup_slow+0x5c/0x150 path_lookupat+0x2ea/0x4d0 filename_lookup+0xbf/0x210 vfs_statx.constprop.0+0x4d/0x110 __do_sys_newlstat+0x3d/0x80 do_syscall_64+0x33/0x40 entry_SYSCALL_64_after_hwframe+0x44/0xa9 ``` The preemption seems to be disabled here: ``` $ scripts/faddr2line mm/z3fold.o z3fold_zpool_malloc+0x463 z3fold_zpool_malloc+0x463/0x6e0: add_to_unbuddied at mm/z3fold.c:645 (inlined by) z3fold_alloc at mm/z3fold.c:1195 (inlined by) z3fold_zpool_malloc at mm/z3fold.c:1737 ``` The call to the rt_spin_lock() seems to be here: ``` $ scripts/faddr2line mm/z3fold.o z3fold_zpool_malloc+0x4c1 z3fold_zpool_malloc+0x4c1/0x6e0: add_to_unbuddied at mm/z3fold.c:649 (inlined by) z3fold_alloc at mm/z3fold.c:1195 (inlined by) z3fold_zpool_malloc at mm/z3fold.c:1737 ``` Or, in source code: ``` 639 /* Add to the appropriate unbuddied list */ 640 static inline void add_to_unbuddied(struct z3fold_pool *pool, 641 struct z3fold_header *zhdr) 642 { 643 if (zhdr->first_chunks == 0 || zhdr->last_chunks == 0 || 644 zhdr->middle_chunks == 0) { 645 struct list_head *unbuddied = get_cpu_ptr(pool->unbuddied); 646 647 int freechunks = num_free_chunks(zhdr); 648 spin_lock(&pool->lock); 649 list_add(&zhdr->buddy, &unbuddied[freechunks]); 650 spin_unlock(&pool->lock); 651 zhdr->cpu = smp_processor_id(); 652 put_cpu_ptr(pool->unbuddied); 653 } 654 } ``` Shouldn't the list manipulation be protected with local_lock+this_cpu_ptr instead of get_cpu_ptr+spin_lock? Thanks. -- Oleksandr Natalenko (post-factum)