Hi Florian, I love your patch! Perhaps something to improve: [auto build test WARNING on nf-next/master] url: https://github.com/0day-ci/linux/commits/Florian-Westphal/netfilter-nf_tables-make-get-and-dump-operations-lockless/20180529-071211 base: https://git.kernel.org/pub/scm/linux/kernel/git/pablo/nf-next.git master reproduce: # apt-get install sparse make ARCH=x86_64 allmodconfig make C=1 CF=-D__CHECK_ENDIAN__ sparse warnings: (new ones prefixed by >>) net/netfilter/nf_tables_api.c:1193:31: sparse: incorrect type in return expression (different address spaces) @@ expected struct nft_stats [noderef] <asn:3>* @@ got sn:3>* @@ net/netfilter/nf_tables_api.c:1193:31: expected struct nft_stats [noderef] <asn:3>* net/netfilter/nf_tables_api.c:1193:31: got void * net/netfilter/nf_tables_api.c:1196:31: sparse: incorrect type in return expression (different address spaces) @@ expected struct nft_stats [noderef] <asn:3>* @@ got sn:3>* @@ net/netfilter/nf_tables_api.c:1196:31: expected struct nft_stats [noderef] <asn:3>* net/netfilter/nf_tables_api.c:1196:31: got void * net/netfilter/nf_tables_api.c:1200:31: sparse: incorrect type in return expression (different address spaces) @@ expected struct nft_stats [noderef] <asn:3>* @@ got sn:3>* @@ net/netfilter/nf_tables_api.c:1200:31: expected struct nft_stats [noderef] <asn:3>* net/netfilter/nf_tables_api.c:1200:31: got void * net/netfilter/nf_tables_api.c:1223:28: sparse: cast between address spaces (<asn:3>-><asn:4>) net/netfilter/nf_tables_api.c:1223:28: sparse: incompatible types in comparison expression (different address spaces) net/netfilter/nf_tables_api.c:1472:23: sparse: incorrect type in assignment (different address spaces) @@ expected struct nft_stats *stats @@ got struct nft_stats struct nft_stats *stats @@ net/netfilter/nf_tables_api.c:1480:29: sparse: incorrect type in argument 1 (different address spaces) @@ expected void [noderef] <asn:3>*__pdata @@ got [noderef] <asn:3>*__pdata @@ net/netfilter/nf_tables_api.c:1484:38: sparse: incorrect type in assignment (different address spaces) @@ expected struct nft_stats [noderef] <asn:3>*stats @@ got [noderef] <asn:3>*stats @@ net/netfilter/nf_tables_api.c:1498:37: sparse: incorrect type in argument 1 (different address spaces) @@ expected void [noderef] <asn:3>*__pdata @@ got [noderef] <asn:3>*__pdata @@ net/netfilter/nf_tables_api.c:2772:16: sparse: incorrect type in return expression (different base types) @@ expected unsigned long long @@ got restricted unsigned long long @@ net/netfilter/nf_tables_api.c:2822:47: sparse: incorrect type in argument 3 (different base types) @@ expected restricted __be64 [usertype] value @@ got __be64 [usertype] value @@ net/netfilter/nf_tables_api.c:3481:47: sparse: incorrect type in argument 3 (different base types) @@ expected restricted __be64 [usertype] value @@ got __be64 [usertype] value @@ net/netfilter/nf_tables_api.c:3495:55: sparse: incorrect type in argument 3 (different base types) @@ expected restricted __be64 [usertype] value @@ got __be64 [usertype] value @@ >> include/linux/rcupdate.h:686:9: sparse: context imbalance in 'nft_netlink_dump_start_rcu' - unexpected unlock vim +/nft_netlink_dump_start_rcu +686 include/linux/rcupdate.h ^1da177e4 Linus Torvalds 2005-04-16 636 ^1da177e4 Linus Torvalds 2005-04-16 637 /* ^1da177e4 Linus Torvalds 2005-04-16 638 * So where is rcu_write_lock()? It does not exist, as there is no ^1da177e4 Linus Torvalds 2005-04-16 639 * way for writers to lock out RCU readers. This is a feature, not ^1da177e4 Linus Torvalds 2005-04-16 640 * a bug -- this property is what provides RCU's performance benefits. ^1da177e4 Linus Torvalds 2005-04-16 641 * Of course, writers must coordinate with each other. The normal ^1da177e4 Linus Torvalds 2005-04-16 642 * spinlock primitives work well for this, but any other technique may be ^1da177e4 Linus Torvalds 2005-04-16 643 * used as well. RCU does not care how the writers keep out of each ^1da177e4 Linus Torvalds 2005-04-16 644 * others' way, as long as they do so. ^1da177e4 Linus Torvalds 2005-04-16 645 */ 3d76c0829 Paul E. McKenney 2009-09-28 646 3d76c0829 Paul E. McKenney 2009-09-28 647 /** ca5ecddfa Paul E. McKenney 2010-04-28 648 * rcu_read_unlock() - marks the end of an RCU read-side critical section. 3d76c0829 Paul E. McKenney 2009-09-28 649 * f27bc4873 Paul E. McKenney 2014-05-04 650 * In most situations, rcu_read_unlock() is immune from deadlock. f27bc4873 Paul E. McKenney 2014-05-04 651 * However, in kernels built with CONFIG_RCU_BOOST, rcu_read_unlock() f27bc4873 Paul E. McKenney 2014-05-04 652 * is responsible for deboosting, which it does via rt_mutex_unlock(). f27bc4873 Paul E. McKenney 2014-05-04 653 * Unfortunately, this function acquires the scheduler's runqueue and f27bc4873 Paul E. McKenney 2014-05-04 654 * priority-inheritance spinlocks. This means that deadlock could result f27bc4873 Paul E. McKenney 2014-05-04 655 * if the caller of rcu_read_unlock() already holds one of these locks or ce36f2f3e Oleg Nesterov 2014-09-28 656 * any lock that is ever acquired while holding them; or any lock which ce36f2f3e Oleg Nesterov 2014-09-28 657 * can be taken from interrupt context because rcu_boost()->rt_mutex_lock() ce36f2f3e Oleg Nesterov 2014-09-28 658 * does not disable irqs while taking ->wait_lock. f27bc4873 Paul E. McKenney 2014-05-04 659 * f27bc4873 Paul E. McKenney 2014-05-04 660 * That said, RCU readers are never priority boosted unless they were f27bc4873 Paul E. McKenney 2014-05-04 661 * preempted. Therefore, one way to avoid deadlock is to make sure f27bc4873 Paul E. McKenney 2014-05-04 662 * that preemption never happens within any RCU read-side critical f27bc4873 Paul E. McKenney 2014-05-04 663 * section whose outermost rcu_read_unlock() is called with one of f27bc4873 Paul E. McKenney 2014-05-04 664 * rt_mutex_unlock()'s locks held. Such preemption can be avoided in f27bc4873 Paul E. McKenney 2014-05-04 665 * a number of ways, for example, by invoking preempt_disable() before f27bc4873 Paul E. McKenney 2014-05-04 666 * critical section's outermost rcu_read_lock(). f27bc4873 Paul E. McKenney 2014-05-04 667 * f27bc4873 Paul E. McKenney 2014-05-04 668 * Given that the set of locks acquired by rt_mutex_unlock() might change f27bc4873 Paul E. McKenney 2014-05-04 669 * at any time, a somewhat more future-proofed approach is to make sure f27bc4873 Paul E. McKenney 2014-05-04 670 * that that preemption never happens within any RCU read-side critical f27bc4873 Paul E. McKenney 2014-05-04 671 * section whose outermost rcu_read_unlock() is called with irqs disabled. f27bc4873 Paul E. McKenney 2014-05-04 672 * This approach relies on the fact that rt_mutex_unlock() currently only f27bc4873 Paul E. McKenney 2014-05-04 673 * acquires irq-disabled locks. f27bc4873 Paul E. McKenney 2014-05-04 674 * f27bc4873 Paul E. McKenney 2014-05-04 675 * The second of these two approaches is best in most situations, f27bc4873 Paul E. McKenney 2014-05-04 676 * however, the first approach can also be useful, at least to those f27bc4873 Paul E. McKenney 2014-05-04 677 * developers willing to keep abreast of the set of locks acquired by f27bc4873 Paul E. McKenney 2014-05-04 678 * rt_mutex_unlock(). f27bc4873 Paul E. McKenney 2014-05-04 679 * 3d76c0829 Paul E. McKenney 2009-09-28 680 * See rcu_read_lock() for more information. 3d76c0829 Paul E. McKenney 2009-09-28 681 */ bc33f24bd Paul E. McKenney 2009-08-22 682 static inline void rcu_read_unlock(void) bc33f24bd Paul E. McKenney 2009-08-22 683 { f78f5b90c Paul E. McKenney 2015-06-18 684 RCU_LOCKDEP_WARN(!rcu_is_watching(), bde23c689 Heiko Carstens 2012-02-01 685 "rcu_read_unlock() used illegally while idle"); bc33f24bd Paul E. McKenney 2009-08-22 @686 __release(RCU); bc33f24bd Paul E. McKenney 2009-08-22 687 __rcu_read_unlock(); d24209bb6 Paul E. McKenney 2015-01-21 688 rcu_lock_release(&rcu_lock_map); /* Keep acq info for rls diags. */ bc33f24bd Paul E. McKenney 2009-08-22 689 } ^1da177e4 Linus Torvalds 2005-04-16 690 :::::: The code at line 686 was first introduced by commit :::::: bc33f24bdca8b6e97376e3a182ab69e6cdefa989 rcu: Consolidate sparse and lockdep declarations in include/linux/rcupdate.h :::::: TO: Paul E. McKenney <paulmck@xxxxxxxxxxxxxxxxxx> :::::: CC: Ingo Molnar <mingo@xxxxxxx> --- 0-DAY kernel test infrastructure Open Source Technology Center https://lists.01.org/pipermail/kbuild-all Intel Corporation -- To unsubscribe from this list: send the line "unsubscribe netfilter-devel" in the body of a message to majordomo@xxxxxxxxxxxxxxx More majordomo info at http://vger.kernel.org/majordomo-info.html
