[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]

From: kernel test robot
Date: Tue Aug 17 2021 - 20:13:22 EST

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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/commit/?id=32a3c5313cce130c4526507975314b84714b043a
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@xxxxxxxxx>

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();
^ ~~~~~~~~~~~~~~~~~~~~~
>> kernel/rcu/rcutorture.c:1525:16: warning: Value stored to 'preempts_irq' during its initialization is never read [clang-analyzer-deadcode.DeadStores]
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;
> 1525 unsigned long preempts_irq = preempts | RCUTORTURE_RDR_IRQ;
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@xxxxxxxxxxxx

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