Hi Roman, Thank you for the patch! Perhaps something to improve: [auto build test WARNING on linus/master] [also build test WARNING on v4.17-rc5 next-20180517] [if your patch is applied to the wrong git tree, please drop us a note to help improve the system] url: https://github.com/0day-ci/linux/commits/Roman-Pen/InfiniBand-Transport-IBTRS-and-Network-Block-Device-IBNBD/20180520-222445 config: m68k-allmodconfig (attached as .config) compiler: m68k-linux-gnu-gcc (Debian 7.2.0-11) 7.2.0 reproduce: wget https://raw.githubusercontent.com/intel/lkp-tests/master/sbin/make.cross -O ~/bin/make.cross chmod +x ~/bin/make.cross # save the attached .config to linux build tree make.cross ARCH=m68k All warnings (new ones prefixed by >>): In file included from arch/m68k/include/asm/atomic.h:7:0, from include/linux/atomic.h:5, from include/linux/spinlock.h:399, from include/linux/seqlock.h:36, from include/linux/time.h:6, from include/linux/stat.h:19, from include/linux/module.h:10, from drivers/infiniband//ulp/ibtrs/ibtrs-clt.c:34: drivers/infiniband//ulp/ibtrs/ibtrs-clt.c: In function 'ibtrs_clt_remove_path_from_arr': arch/m68k/include/asm/cmpxchg.h:122:3: warning: value computed is not used [-Wunused-value] ((__typeof__(*(ptr)))__cmpxchg((ptr), (unsigned long)(o), \ ~^~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~ (unsigned long)(n), sizeof(*(ptr)))) ~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~ >> drivers/infiniband//ulp/ibtrs/ibtrs-clt.c:1456:3: note: in expansion of macro 'cmpxchg' cmpxchg(ppcpu_path, sess, next); ^~~~~~~ vim +/cmpxchg +1456 drivers/infiniband//ulp/ibtrs/ibtrs-clt.c 44463323 Roman Pen 2018-05-18 1396 44463323 Roman Pen 2018-05-18 1397 static void ibtrs_clt_remove_path_from_arr(struct ibtrs_clt_sess *sess) 44463323 Roman Pen 2018-05-18 1398 { 44463323 Roman Pen 2018-05-18 1399 struct ibtrs_clt *clt = sess->clt; 44463323 Roman Pen 2018-05-18 1400 struct ibtrs_clt_sess *next; 44463323 Roman Pen 2018-05-18 1401 int cpu; 44463323 Roman Pen 2018-05-18 1402 44463323 Roman Pen 2018-05-18 1403 mutex_lock(&clt->paths_mutex); 44463323 Roman Pen 2018-05-18 1404 list_del_rcu(&sess->s.entry); 44463323 Roman Pen 2018-05-18 1405 44463323 Roman Pen 2018-05-18 1406 /* Make sure everybody observes path removal. */ 44463323 Roman Pen 2018-05-18 1407 synchronize_rcu(); 44463323 Roman Pen 2018-05-18 1408 44463323 Roman Pen 2018-05-18 1409 /* 44463323 Roman Pen 2018-05-18 1410 * Decrement paths number only after grace period, because 44463323 Roman Pen 2018-05-18 1411 * caller of do_each_path() must firstly observe list without 44463323 Roman Pen 2018-05-18 1412 * path and only then decremented paths number. 44463323 Roman Pen 2018-05-18 1413 * 44463323 Roman Pen 2018-05-18 1414 * Otherwise there can be the following situation: 44463323 Roman Pen 2018-05-18 1415 * o Two paths exist and IO is coming. 44463323 Roman Pen 2018-05-18 1416 * o One path is removed: 44463323 Roman Pen 2018-05-18 1417 * CPU#0 CPU#1 44463323 Roman Pen 2018-05-18 1418 * do_each_path(): ibtrs_clt_remove_path_from_arr(): 44463323 Roman Pen 2018-05-18 1419 * path = get_next_path() 44463323 Roman Pen 2018-05-18 1420 * ^^^ list_del_rcu(path) 44463323 Roman Pen 2018-05-18 1421 * [!CONNECTED path] clt->paths_num-- 44463323 Roman Pen 2018-05-18 1422 * ^^^^^^^^^ 44463323 Roman Pen 2018-05-18 1423 * load clt->paths_num from 2 to 1 44463323 Roman Pen 2018-05-18 1424 * ^^^^^^^^^ 44463323 Roman Pen 2018-05-18 1425 * sees 1 44463323 Roman Pen 2018-05-18 1426 * 44463323 Roman Pen 2018-05-18 1427 * path is observed as !CONNECTED, but do_each_path() loop 44463323 Roman Pen 2018-05-18 1428 * ends, because expression i < clt->paths_num is false. 44463323 Roman Pen 2018-05-18 1429 */ 44463323 Roman Pen 2018-05-18 1430 clt->paths_num--; 44463323 Roman Pen 2018-05-18 1431 44463323 Roman Pen 2018-05-18 1432 next = list_next_or_null_rr_rcu(&clt->paths_list, &sess->s.entry, 44463323 Roman Pen 2018-05-18 1433 typeof(*next), s.entry); 44463323 Roman Pen 2018-05-18 1434 44463323 Roman Pen 2018-05-18 1435 /* 44463323 Roman Pen 2018-05-18 1436 * Pcpu paths can still point to the path which is going to be 44463323 Roman Pen 2018-05-18 1437 * removed, so change the pointer manually. 44463323 Roman Pen 2018-05-18 1438 */ 44463323 Roman Pen 2018-05-18 1439 for_each_possible_cpu(cpu) { 44463323 Roman Pen 2018-05-18 1440 struct ibtrs_clt_sess **ppcpu_path; 44463323 Roman Pen 2018-05-18 1441 44463323 Roman Pen 2018-05-18 1442 ppcpu_path = per_cpu_ptr(clt->pcpu_path, cpu); 44463323 Roman Pen 2018-05-18 1443 if (*ppcpu_path != sess) 44463323 Roman Pen 2018-05-18 1444 /* 44463323 Roman Pen 2018-05-18 1445 * synchronize_rcu() was called just after deleting 44463323 Roman Pen 2018-05-18 1446 * entry from the list, thus IO code path cannot 44463323 Roman Pen 2018-05-18 1447 * change pointer back to the pointer which is going 44463323 Roman Pen 2018-05-18 1448 * to be removed, we are safe here. 44463323 Roman Pen 2018-05-18 1449 */ 44463323 Roman Pen 2018-05-18 1450 continue; 44463323 Roman Pen 2018-05-18 1451 44463323 Roman Pen 2018-05-18 1452 /* 44463323 Roman Pen 2018-05-18 1453 * We race with IO code path, which also changes pointer, 44463323 Roman Pen 2018-05-18 1454 * thus we have to be careful not to override it. 44463323 Roman Pen 2018-05-18 1455 */ 44463323 Roman Pen 2018-05-18 @1456 cmpxchg(ppcpu_path, sess, next); 44463323 Roman Pen 2018-05-18 1457 } 44463323 Roman Pen 2018-05-18 1458 mutex_unlock(&clt->paths_mutex); 44463323 Roman Pen 2018-05-18 1459 } 44463323 Roman Pen 2018-05-18 1460 :::::: The code at line 1456 was first introduced by commit :::::: 4446332354bf8cf878755e55a221c59eb55a0f1f ibtrs: client: main functionality :::::: TO: Roman Pen <roman.penyaev@xxxxxxxxxxxxxxxx> :::::: CC: 0day robot <lkp@xxxxxxxxx> --- 0-DAY kernel test infrastructure Open Source Technology Center https://lists.01.org/pipermail/kbuild-all Intel Corporation
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