[kbuild-all] [linux-rt-devel:linux-5.14.y-rt-rebase 194/245] kernel/rcu/rcutorture.c:1525:16: warning: Value stored to 'preempts_irq' during its initialization is never read [clang-analyzer-deadcode.DeadStores]

tree: https://git.kernel.org/pub/scm/linux/kernel/git/rt/linux-rt-devel.git linux-5.14.y-rt-rebase head: 0eead4e5a60cb716ec911a552787a69332cf6943 commit: 32a3c5313cce130c4526507975314b84714b043a [194/245] rcutorture: Avoid problematic critical section nesting on RT config: mips-randconfig-c004-20210816 (attached as .config) compiler: clang version 14.0.0 (https://github.com/llvm/llvm-project 44d0a99a12ec7ead4d2f5ef649ba05b40f6d463d) reproduce (this is a W=1 build): wget https://raw.githubusercontent.com/intel/lkp-tests/master/sbin/make.cross -O ~/bin/make.cross chmod +x ~/bin/make.cross # install mips cross compiling tool for clang build # apt-get install binutils-mips-linux-gnu # https://git.kernel.org/pub/scm/linux/kernel/git/rt/linux-rt-devel.git/com... git remote add linux-rt-devel https://git.kernel.org/pub/scm/linux/kernel/git/rt/linux-rt-devel.git git fetch --no-tags linux-rt-devel linux-5.14.y-rt-rebase git checkout 32a3c5313cce130c4526507975314b84714b043a # save the attached .config to linux build tree COMPILER_INSTALL_PATH=$HOME/0day COMPILER=clang make.cross ARCH=mips clang-analyzer If you fix the issue, kindly add following tag as appropriate Reported-by: kernel test robot <lkp(a)intel.com&gt; clang-analyzer warnings: (new ones prefixed by >>) ^ kernel/rcu/rcutorture.c:1734:9: note: Calling 'timer_pending' if (!timer_pending(&t)) ^~~~~~~~~~~~~~~~~ include/linux/timer.h:168:10: note: Calling 'hlist_unhashed_lockless' return !hlist_unhashed_lockless(&timer->entry); ^~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~ include/linux/list.h:821:10: note: Left side of '||' is false return !READ_ONCE(h->pprev); ^ include/asm-generic/rwonce.h:49:2: note: expanded from macro 'READ_ONCE' compiletime_assert_rwonce_type(x); \ ^ include/asm-generic/rwonce.h:36:21: note: expanded from macro 'compiletime_assert_rwonce_type' compiletime_assert(__native_word(t) || sizeof(t) == sizeof(long long), \ ^ include/linux/compiler_types.h:290:3: note: expanded from macro '__native_word' (sizeof(t) == sizeof(char) || sizeof(t) == sizeof(short) || \ ^ include/linux/list.h:821:10: note: Left side of '||' is false return !READ_ONCE(h->pprev); ^ include/asm-generic/rwonce.h:49:2: note: expanded from macro 'READ_ONCE' compiletime_assert_rwonce_type(x); \ ^ include/asm-generic/rwonce.h:36:21: note: expanded from macro 'compiletime_assert_rwonce_type' compiletime_assert(__native_word(t) || sizeof(t) == sizeof(long long), \ ^ include/linux/compiler_types.h:290:3: note: expanded from macro '__native_word' (sizeof(t) == sizeof(char) || sizeof(t) == sizeof(short) || \ ^ include/linux/list.h:821:10: note: Left side of '||' is true return !READ_ONCE(h->pprev); ^ include/asm-generic/rwonce.h:49:2: note: expanded from macro 'READ_ONCE' compiletime_assert_rwonce_type(x); \ ^ include/asm-generic/rwonce.h:36:21: note: expanded from macro 'compiletime_assert_rwonce_type' compiletime_assert(__native_word(t) || sizeof(t) == sizeof(long long), \ ^ include/linux/compiler_types.h:291:28: note: expanded from macro '__native_word' sizeof(t) == sizeof(int) || sizeof(t) == sizeof(long)) ^ include/linux/list.h:821:10: note: Taking false branch return !READ_ONCE(h->pprev); ^ include/asm-generic/rwonce.h:49:2: note: expanded from macro 'READ_ONCE' compiletime_assert_rwonce_type(x); \ ^ include/asm-generic/rwonce.h:36:2: note: expanded from macro 'compiletime_assert_rwonce_type' compiletime_assert(__native_word(t) || sizeof(t) == sizeof(long long), \ ^ include/linux/compiler_types.h:328:2: note: expanded from macro 'compiletime_assert' _compiletime_assert(condition, msg, __compiletime_assert_, __COUNTER__) ^ include/linux/compiler_types.h:316:2: note: expanded from macro '_compiletime_assert' __compiletime_assert(condition, msg, prefix, suffix) ^ include/linux/compiler_types.h:308:3: note: expanded from macro '__compiletime_assert' if (!(condition)) \ ^ include/linux/list.h:821:10: note: Loop condition is false. Exiting loop return !READ_ONCE(h->pprev); ^ include/asm-generic/rwonce.h:49:2: note: expanded from macro 'READ_ONCE' compiletime_assert_rwonce_type(x); \ ^ include/asm-generic/rwonce.h:36:2: note: expanded from macro 'compiletime_assert_rwonce_type' compiletime_assert(__native_word(t) || sizeof(t) == sizeof(long long), \ ^ include/linux/compiler_types.h:328:2: note: expanded from macro 'compiletime_assert' _compiletime_assert(condition, msg, __compiletime_assert_, __COUNTER__) ^ include/linux/compiler_types.h:316:2: note: expanded from macro '_compiletime_assert' __compiletime_assert(condition, msg, prefix, suffix) ^ include/linux/compiler_types.h:306:2: note: expanded from macro '__compiletime_assert' do { \ ^ include/linux/list.h:821:2: note: Undefined or garbage value returned to caller return !READ_ONCE(h->pprev); ^ ~~~~~~~~~~~~~~~~~~~~ kernel/rcu/rcutorture.c:387:3: warning: Value stored to 'started' is never read [clang-analyzer-deadcode.DeadStores] started = cur_ops->get_gp_seq(); ^ ~~~~~~~~~~~~~~~~~~~~~ kernel/rcu/rcutorture.c:387:3: note: Value stored to 'started' is never read started = cur_ops->get_gp_seq(); ^ ~~~~~~~~~~~~~~~~~~~~~ kernel/rcu/rcutorture.c:388:3: warning: Value stored to 'ts' is never read [clang-analyzer-deadcode.DeadStores] ts = rcu_trace_clock_local(); ^ ~~~~~~~~~~~~~~~~~~~~~~~ kernel/rcu/rcutorture.c:388:3: note: Value stored to 'ts' is never read ts = rcu_trace_clock_local(); ^ ~~~~~~~~~~~~~~~~~~~~~~~ kernel/rcu/rcutorture.c:393:3: warning: Value stored to 'completed' is never read [clang-analyzer-deadcode.DeadStores] completed = cur_ops->get_gp_seq(); ^ ~~~~~~~~~~~~~~~~~~~~~ kernel/rcu/rcutorture.c:393:3: note: Value stored to 'completed' is never read completed = cur_ops->get_gp_seq(); ^ ~~~~~~~~~~~~~~~~~~~~~ unsigned long preempts_irq = preempts | RCUTORTURE_RDR_IRQ; ^~~~~~~~~~~~ ~~~~~~~~~~~~~~~~~~~~~~~~~~~~~ kernel/rcu/rcutorture.c:1525:16: note: Value stored to 'preempts_irq' during its initialization is never read unsigned long preempts_irq = preempts | RCUTORTURE_RDR_IRQ; ^~~~~~~~~~~~ ~~~~~~~~~~~~~~~~~~~~~~~~~~~~~ kernel/rcu/rcutorture.c:1634:2: warning: Value stored to 'ts' is never read [clang-analyzer-deadcode.DeadStores] ts = rcu_trace_clock_local(); ^ ~~~~~~~~~~~~~~~~~~~~~~~ kernel/rcu/rcutorture.c:1634:2: note: Value stored to 'ts' is never read ts = rcu_trace_clock_local(); ^ ~~~~~~~~~~~~~~~~~~~~~~~ kernel/rcu/rcutorture.c:1667:13: warning: 1st function call argument is an uninitialized value [clang-analyzer-core.CallAndMessage] WARN_ONCE(cur_ops->poll_gp_state(cookie), ^ include/asm-generic/bug.h:150:18: note: expanded from macro 'WARN_ONCE' DO_ONCE_LITE_IF(condition, WARN, 1, format) ^~~~~~~~~ include/linux/once_lite.h:15:27: note: expanded from macro 'DO_ONCE_LITE_IF' bool __ret_do_once = !!(condition); \ ^~~~~~~~~ kernel/rcu/rcutorture.c:1615:2: note: 'cookie' declared without an initial value unsigned long cookie; ^~~~~~~~~~~~~~~~~~~~ kernel/rcu/rcutorture.c:1628:2: note: '__ret_do_once' is false WARN_ON_ONCE(!rcu_is_watching()); ^ include/asm-generic/bug.h:146:2: note: expanded from macro 'WARN_ON_ONCE' DO_ONCE_LITE_IF(condition, WARN_ON, 1) ^~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~ include/linux/once_lite.h:17:16: note: expanded from macro 'DO_ONCE_LITE_IF' if (unlikely(__ret_do_once && !__already_done)) { \ ^~~~~~~~~~~~~ include/linux/compiler.h:78:42: note: expanded from macro 'unlikely' # define unlikely(x) __builtin_expect(!!(x), 0) ^ kernel/rcu/rcutorture.c:1628:2: note: Left side of '&&' is false WARN_ON_ONCE(!rcu_is_watching()); ^ include/asm-generic/bug.h:146:2: note: expanded from macro 'WARN_ON_ONCE' DO_ONCE_LITE_IF(condition, WARN_ON, 1) ^ include/linux/once_lite.h:17:30: note: expanded from macro 'DO_ONCE_LITE_IF' if (unlikely(__ret_do_once && !__already_done)) { \ ^ kernel/rcu/rcutorture.c:1628:2: note: Taking false branch WARN_ON_ONCE(!rcu_is_watching()); ^ include/asm-generic/bug.h:146:2: note: expanded from macro 'WARN_ON_ONCE' DO_ONCE_LITE_IF(condition, WARN_ON, 1) ^ include/linux/once_lite.h:17:3: note: expanded from macro 'DO_ONCE_LITE_IF' if (unlikely(__ret_do_once && !__already_done)) { \ ^ kernel/rcu/rcutorture.c:1631:6: note: Assuming field 'get_gp_state' is null if (cur_ops->get_gp_state && cur_ops->poll_gp_state) ^~~~~~~~~~~~~~~~~~~~~ kernel/rcu/rcutorture.c:1631:28: note: Left side of '&&' is false if (cur_ops->get_gp_state && cur_ops->poll_gp_state) ^ kernel/rcu/rcutorture.c:1635:6: note: Left side of '||' is false p = rcu_dereference_check(rcu_torture_current, ^ include/linux/rcupdate.h:542:2: note: expanded from macro 'rcu_dereference_check' __rcu_dereference_check((p), (c) || rcu_read_lock_held(), __rcu) ^ include/linux/rcupdate.h:403:48: note: expanded from macro '__rcu_dereference_check' typeof(*p) *________p1 = (typeof(*p) *__force)READ_ONCE(p); \ ^ include/asm-generic/rwonce.h:49:2: note: expanded from macro 'READ_ONCE' compiletime_assert_rwonce_type(x); \ ^ include/asm-generic/rwonce.h:36:21: note: expanded from macro 'compiletime_assert_rwonce_type' compiletime_assert(__native_word(t) || sizeof(t) == sizeof(long long), \ ^ include/linux/compiler_types.h:290:3: note: expanded from macro '__native_word' (sizeof(t) == sizeof(char) || sizeof(t) == sizeof(short) || \ ^ kernel/rcu/rcutorture.c:1635:6: note: Left side of '||' is false p = rcu_dereference_check(rcu_torture_current, ^ include/linux/rcupdate.h:542:2: note: expanded from macro 'rcu_dereference_check' __rcu_dereference_check((p), (c) || rcu_read_lock_held(), __rcu) ^ include/linux/rcupdate.h:403:48: note: expanded from macro '__rcu_dereference_check' typeof(*p) *________p1 = (typeof(*p) *__force)READ_ONCE(p); \ ^ include/asm-generic/rwonce.h:49:2: note: expanded from macro 'READ_ONCE' compiletime_assert_rwonce_type(x); \ ^ include/asm-generic/rwonce.h:36:21: note: expanded from macro 'compiletime_assert_rwonce_type' compiletime_assert(__native_word(t) || sizeof(t) == sizeof(long long), \ ^ include/linux/compiler_types.h:290:3: note: expanded from macro '__native_word' (sizeof(t) == sizeof(char) || sizeof(t) == sizeof(short) || \ ^ kernel/rcu/rcutorture.c:1635:6: note: Left side of '||' is true p = rcu_dereference_check(rcu_torture_current, ^ include/linux/rcupdate.h:542:2: note: expanded from macro 'rcu_dereference_check' __rcu_dereference_check((p), (c) || rcu_read_lock_held(), __rcu) vim +/preempts_irq +1525 kernel/rcu/rcutorture.c 1516 1517 /* Return a random protection state mask, but with at least one bit set. */ 1518 static int 1519 rcutorture_extend_mask(int oldmask, struct torture_random_state *trsp) 1520 { 1521 int mask = rcutorture_extend_mask_max(); 1522 unsigned long randmask1 = torture_random(trsp) >> 8; 1523 unsigned long randmask2 = randmask1 >> 3; 1524 unsigned long preempts = RCUTORTURE_RDR_PREEMPT | RCUTORTURE_RDR_SCHED; 1526 unsigned long nonatomic_bhs = RCUTORTURE_RDR_BH | RCUTORTURE_RDR_RBH; 1527 unsigned long atomic_bhs = RCUTORTURE_RDR_ATOM_BH | 1528 RCUTORTURE_RDR_ATOM_RBH; 1529 unsigned long tmp; 1530 1531 WARN_ON_ONCE(mask >> RCUTORTURE_RDR_SHIFT); 1532 /* Mostly only one bit (need preemption!), sometimes lots of bits. */ 1533 if (!(randmask1 & 0x7)) 1534 mask = mask & randmask2; 1535 else 1536 mask = mask & (1 << (randmask2 % RCUTORTURE_RDR_NBITS)); 1537 1538 /* 1539 * Can't enable bh w/irq disabled. 1540 */ 1541 tmp = atomic_bhs | nonatomic_bhs; 1542 if (mask & RCUTORTURE_RDR_IRQ) 1543 mask |= oldmask & tmp; 1544 1545 /* 1546 * Ideally these sequences would be detected in debug builds 1547 * (regardless of RT), but until then don't stop testing 1548 * them on non-RT. 1549 */ 1550 if (IS_ENABLED(CONFIG_PREEMPT_RT)) { 1551 /* 1552 * Can't release the outermost rcu lock in an irq disabled 1553 * section without preemption also being disabled, if irqs 1554 * had ever been enabled during this RCU critical section 1555 * (could leak a special flag and delay reporting the qs). 1556 */ 1557 if ((oldmask & RCUTORTURE_RDR_RCU) && 1558 (mask & RCUTORTURE_RDR_IRQ) && 1559 !(mask & preempts)) 1560 mask |= RCUTORTURE_RDR_RCU; 1561 1562 /* Can't modify atomic bh in non-atomic context */ 1563 if ((oldmask & atomic_bhs) && (mask & atomic_bhs) && 1564 !(mask & preempts_irq)) { 1565 mask |= oldmask & preempts_irq; 1566 if (mask & RCUTORTURE_RDR_IRQ) 1567 mask |= oldmask & tmp; 1568 } 1569 if ((mask & atomic_bhs) && !(mask & preempts_irq)) 1570 mask |= RCUTORTURE_RDR_PREEMPT; 1571 1572 /* Can't modify non-atomic bh in atomic context */ 1573 tmp = nonatomic_bhs; 1574 if (oldmask & preempts_irq) 1575 mask &= ~tmp; 1576 if ((oldmask | mask) & preempts_irq) 1577 mask |= oldmask & tmp; 1578 } 1579 1580 return mask ?: RCUTORTURE_RDR_RCU; 1581 } 1582 --- 0-DAY CI Kernel Test Service, Intel Corporation https://lists.01.org/hyperkitty/list/kbuild-all@lists.01.org