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Subjectlib/llist.c:33:11: warning: converting the result of '<<' to a boolean always evaluates to true
Hi Nathan,

First bad commit (maybe != root cause):

tree: https://git.kernel.org/pub/scm/linux/kernel/git/torvalds/linux.git master
head: 65f0d2414b7079556fbbcc070b3d1c9f9587606d
commit: afe956c577b2d5a3d9834e4424587c1ebcf90c4c kbuild: Enable -Wtautological-compare
date: 9 months ago
config: mips-randconfig-r026-20210114 (attached as .config)
compiler: clang version 12.0.0 (https://github.com/llvm/llvm-project 68ff52ffead2ba25cca442778ab19286000daad7)
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/torvalds/linux.git/commit/?id=afe956c577b2d5a3d9834e4424587c1ebcf90c4c
git remote add linus https://git.kernel.org/pub/scm/linux/kernel/git/torvalds/linux.git
git fetch --no-tags linus master
git checkout afe956c577b2d5a3d9834e4424587c1ebcf90c4c
# save the attached .config to linux build tree
COMPILER_INSTALL_PATH=$HOME/0day COMPILER=clang make.cross ARCH=mips

If you fix the issue, kindly add following tag as appropriate
Reported-by: kernel test robot <lkp@intel.com>

All warnings (new ones prefixed by >>):

In file included from include/linux/llist.h:51:
In file included from include/linux/atomic.h:7:
arch/mips/include/asm/atomic.h:49:1: warning: converting the result of '<<' to a boolean always evaluates to true [-Wtautological-constant-compare]
arch/mips/include/asm/atomic.h:40:9: note: expanded from macro 'ATOMIC_OPS'
return cmpxchg(&v->counter, o, n); \
^
arch/mips/include/asm/cmpxchg.h:204:7: note: expanded from macro 'cmpxchg'
if (!__SYNC_loongson3_war) \
^
arch/mips/include/asm/sync.h:147:34: note: expanded from macro '__SYNC_loongson3_war'
# define __SYNC_loongson3_war (1 << 31)
^
In file included from lib/llist.c:15:
In file included from include/linux/llist.h:51:
In file included from include/linux/atomic.h:7:
arch/mips/include/asm/atomic.h:49:1: warning: converting the result of '<<' to a boolean always evaluates to true [-Wtautological-constant-compare]
arch/mips/include/asm/atomic.h:45:9: note: expanded from macro 'ATOMIC_OPS'
return xchg(&v->counter, n); \
^
arch/mips/include/asm/cmpxchg.h:102:7: note: expanded from macro 'xchg'
if (!__SYNC_loongson3_war) \
^
arch/mips/include/asm/sync.h:147:34: note: expanded from macro '__SYNC_loongson3_war'
# define __SYNC_loongson3_war (1 << 31)
^
In file included from lib/llist.c:15:
In file included from include/linux/llist.h:51:
In file included from include/linux/atomic.h:7:
arch/mips/include/asm/atomic.h:53:1: warning: converting the result of '<<' to a boolean always evaluates to true [-Wtautological-constant-compare]
ATOMIC_OPS(atomic64, s64)
^
arch/mips/include/asm/atomic.h:40:9: note: expanded from macro 'ATOMIC_OPS'
return cmpxchg(&v->counter, o, n); \
^
arch/mips/include/asm/cmpxchg.h:194:7: note: expanded from macro 'cmpxchg'
if (!__SYNC_loongson3_war) \
^
arch/mips/include/asm/sync.h:147:34: note: expanded from macro '__SYNC_loongson3_war'
# define __SYNC_loongson3_war (1 << 31)
^
In file included from lib/llist.c:15:
In file included from include/linux/llist.h:51:
In file included from include/linux/atomic.h:7:
arch/mips/include/asm/atomic.h:53:1: warning: converting the result of '<<' to a boolean always evaluates to true [-Wtautological-constant-compare]
arch/mips/include/asm/atomic.h:40:9: note: expanded from macro 'ATOMIC_OPS'
return cmpxchg(&v->counter, o, n); \
^
arch/mips/include/asm/cmpxchg.h:204:7: note: expanded from macro 'cmpxchg'
if (!__SYNC_loongson3_war) \
^
arch/mips/include/asm/sync.h:147:34: note: expanded from macro '__SYNC_loongson3_war'
# define __SYNC_loongson3_war (1 << 31)
^
In file included from lib/llist.c:15:
In file included from include/linux/llist.h:51:
In file included from include/linux/atomic.h:7:
arch/mips/include/asm/atomic.h:53:1: warning: converting the result of '<<' to a boolean always evaluates to true [-Wtautological-constant-compare]
arch/mips/include/asm/atomic.h:45:9: note: expanded from macro 'ATOMIC_OPS'
return xchg(&v->counter, n); \
^
arch/mips/include/asm/cmpxchg.h:102:7: note: expanded from macro 'xchg'
if (!__SYNC_loongson3_war) \
^
arch/mips/include/asm/sync.h:147:34: note: expanded from macro '__SYNC_loongson3_war'
# define __SYNC_loongson3_war (1 << 31)
^
In file included from lib/llist.c:15:
In file included from include/linux/llist.h:51:
In file included from include/linux/atomic.h:7:
arch/mips/include/asm/atomic.h:258:1: warning: converting the result of '<<' to a boolean always evaluates to true [-Wtautological-constant-compare]
ATOMIC_SIP_OP(atomic, int, subu, ll, sc)
^
arch/mips/include/asm/atomic.h:252:7: note: expanded from macro 'ATOMIC_SIP_OP'
if (!__SYNC_loongson3_war) \
^
arch/mips/include/asm/sync.h:147:34: note: expanded from macro '__SYNC_loongson3_war'
# define __SYNC_loongson3_war (1 << 31)
^
In file included from lib/llist.c:15:
In file included from include/linux/llist.h:51:
In file included from include/linux/atomic.h:7:
arch/mips/include/asm/atomic.h:262:1: warning: converting the result of '<<' to a boolean always evaluates to true [-Wtautological-constant-compare]
ATOMIC_SIP_OP(atomic64, s64, dsubu, lld, scd)
^
arch/mips/include/asm/atomic.h:252:7: note: expanded from macro 'ATOMIC_SIP_OP'
if (!__SYNC_loongson3_war) \
^
arch/mips/include/asm/sync.h:147:34: note: expanded from macro '__SYNC_loongson3_war'
# define __SYNC_loongson3_war (1 << 31)
^
In file included from lib/llist.c:15:
include/linux/llist.h:222:9: warning: converting the result of '<<' to a boolean always evaluates to true [-Wtautological-constant-compare]
return xchg(&head->first, NULL);
^
arch/mips/include/asm/cmpxchg.h:102:7: note: expanded from macro 'xchg'
if (!__SYNC_loongson3_war) \
^
arch/mips/include/asm/sync.h:147:34: note: expanded from macro '__SYNC_loongson3_war'
# define __SYNC_loongson3_war (1 << 31)
^
>> lib/llist.c:33:11: warning: converting the result of '<<' to a boolean always evaluates to true [-Wtautological-constant-compare]
} while (cmpxchg(&head->first, first, new_first) != first);
^
arch/mips/include/asm/cmpxchg.h:194:7: note: expanded from macro 'cmpxchg'
if (!__SYNC_loongson3_war) \
^
arch/mips/include/asm/sync.h:147:34: note: expanded from macro '__SYNC_loongson3_war'
# define __SYNC_loongson3_war (1 << 31)
^
>> lib/llist.c:33:11: warning: converting the result of '<<' to a boolean always evaluates to true [-Wtautological-constant-compare]
arch/mips/include/asm/cmpxchg.h:204:7: note: expanded from macro 'cmpxchg'
if (!__SYNC_loongson3_war) \
^
arch/mips/include/asm/sync.h:147:34: note: expanded from macro '__SYNC_loongson3_war'
# define __SYNC_loongson3_war (1 << 31)
^
lib/llist.c:63:11: warning: converting the result of '<<' to a boolean always evaluates to true [-Wtautological-constant-compare]
entry = cmpxchg(&head->first, old_entry, next);
^
arch/mips/include/asm/cmpxchg.h:194:7: note: expanded from macro 'cmpxchg'
if (!__SYNC_loongson3_war) \
^
arch/mips/include/asm/sync.h:147:34: note: expanded from macro '__SYNC_loongson3_war'
# define __SYNC_loongson3_war (1 << 31)
^
lib/llist.c:63:11: warning: converting the result of '<<' to a boolean always evaluates to true [-Wtautological-constant-compare]
arch/mips/include/asm/cmpxchg.h:204:7: note: expanded from macro 'cmpxchg'
if (!__SYNC_loongson3_war) \
^
arch/mips/include/asm/sync.h:147:34: note: expanded from macro '__SYNC_loongson3_war'
# define __SYNC_loongson3_war (1 << 31)
^
13 warnings generated.
Assembler messages:
Fatal error: invalid -march= option: `mips64r2'
clang-12: error: assembler command failed with exit code 1 (use -v to see invocation)
--
In file included from lib/errseq.c:4:
In file included from include/linux/atomic.h:7:
arch/mips/include/asm/atomic.h:49:1: warning: converting the result of '<<' to a boolean always evaluates to true [-Wtautological-constant-compare]
ATOMIC_OPS(atomic, int)
^
arch/mips/include/asm/atomic.h:40:9: note: expanded from macro 'ATOMIC_OPS'
return cmpxchg(&v->counter, o, n); \
^
arch/mips/include/asm/cmpxchg.h:194:7: note: expanded from macro 'cmpxchg'
if (!__SYNC_loongson3_war) \
^
arch/mips/include/asm/sync.h:147:34: note: expanded from macro '__SYNC_loongson3_war'
# define __SYNC_loongson3_war (1 << 31)
^
In file included from lib/errseq.c:4:
In file included from include/linux/atomic.h:7:
arch/mips/include/asm/atomic.h:49:1: warning: converting the result of '<<' to a boolean always evaluates to true [-Wtautological-constant-compare]
arch/mips/include/asm/atomic.h:40:9: note: expanded from macro 'ATOMIC_OPS'
return cmpxchg(&v->counter, o, n); \
^
arch/mips/include/asm/cmpxchg.h:204:7: note: expanded from macro 'cmpxchg'
if (!__SYNC_loongson3_war) \
^
arch/mips/include/asm/sync.h:147:34: note: expanded from macro '__SYNC_loongson3_war'
# define __SYNC_loongson3_war (1 << 31)
^
In file included from lib/errseq.c:4:
In file included from include/linux/atomic.h:7:
arch/mips/include/asm/atomic.h:49:1: warning: converting the result of '<<' to a boolean always evaluates to true [-Wtautological-constant-compare]
arch/mips/include/asm/atomic.h:45:9: note: expanded from macro 'ATOMIC_OPS'
return xchg(&v->counter, n); \
^
arch/mips/include/asm/cmpxchg.h:102:7: note: expanded from macro 'xchg'
if (!__SYNC_loongson3_war) \
^
arch/mips/include/asm/sync.h:147:34: note: expanded from macro '__SYNC_loongson3_war'
# define __SYNC_loongson3_war (1 << 31)
^
In file included from lib/errseq.c:4:
In file included from include/linux/atomic.h:7:
arch/mips/include/asm/atomic.h:53:1: warning: converting the result of '<<' to a boolean always evaluates to true [-Wtautological-constant-compare]
ATOMIC_OPS(atomic64, s64)
^
arch/mips/include/asm/atomic.h:40:9: note: expanded from macro 'ATOMIC_OPS'
return cmpxchg(&v->counter, o, n); \
^
arch/mips/include/asm/cmpxchg.h:194:7: note: expanded from macro 'cmpxchg'
if (!__SYNC_loongson3_war) \
^
arch/mips/include/asm/sync.h:147:34: note: expanded from macro '__SYNC_loongson3_war'
# define __SYNC_loongson3_war (1 << 31)
^
In file included from lib/errseq.c:4:
In file included from include/linux/atomic.h:7:
arch/mips/include/asm/atomic.h:53:1: warning: converting the result of '<<' to a boolean always evaluates to true [-Wtautological-constant-compare]
arch/mips/include/asm/atomic.h:40:9: note: expanded from macro 'ATOMIC_OPS'
return cmpxchg(&v->counter, o, n); \
^
arch/mips/include/asm/cmpxchg.h:204:7: note: expanded from macro 'cmpxchg'
if (!__SYNC_loongson3_war) \
^
arch/mips/include/asm/sync.h:147:34: note: expanded from macro '__SYNC_loongson3_war'
# define __SYNC_loongson3_war (1 << 31)
^
In file included from lib/errseq.c:4:
In file included from include/linux/atomic.h:7:
arch/mips/include/asm/atomic.h:53:1: warning: converting the result of '<<' to a boolean always evaluates to true [-Wtautological-constant-compare]
arch/mips/include/asm/atomic.h:45:9: note: expanded from macro 'ATOMIC_OPS'
return xchg(&v->counter, n); \
^
arch/mips/include/asm/cmpxchg.h:102:7: note: expanded from macro 'xchg'
if (!__SYNC_loongson3_war) \
^
arch/mips/include/asm/sync.h:147:34: note: expanded from macro '__SYNC_loongson3_war'
# define __SYNC_loongson3_war (1 << 31)
^
In file included from lib/errseq.c:4:
In file included from include/linux/atomic.h:7:
arch/mips/include/asm/atomic.h:258:1: warning: converting the result of '<<' to a boolean always evaluates to true [-Wtautological-constant-compare]
ATOMIC_SIP_OP(atomic, int, subu, ll, sc)
^
arch/mips/include/asm/atomic.h:252:7: note: expanded from macro 'ATOMIC_SIP_OP'
if (!__SYNC_loongson3_war) \
^
arch/mips/include/asm/sync.h:147:34: note: expanded from macro '__SYNC_loongson3_war'
# define __SYNC_loongson3_war (1 << 31)
^
In file included from lib/errseq.c:4:
In file included from include/linux/atomic.h:7:
arch/mips/include/asm/atomic.h:262:1: warning: converting the result of '<<' to a boolean always evaluates to true [-Wtautological-constant-compare]
ATOMIC_SIP_OP(atomic64, s64, dsubu, lld, scd)
^
arch/mips/include/asm/atomic.h:252:7: note: expanded from macro 'ATOMIC_SIP_OP'
if (!__SYNC_loongson3_war) \
^
arch/mips/include/asm/sync.h:147:34: note: expanded from macro '__SYNC_loongson3_war'
# define __SYNC_loongson3_war (1 << 31)
^
>> lib/errseq.c:94:9: warning: converting the result of '<<' to a boolean always evaluates to true [-Wtautological-constant-compare]
cur = cmpxchg(eseq, old, new);
^
arch/mips/include/asm/cmpxchg.h:194:7: note: expanded from macro 'cmpxchg'
if (!__SYNC_loongson3_war) \
^
arch/mips/include/asm/sync.h:147:34: note: expanded from macro '__SYNC_loongson3_war'
# define __SYNC_loongson3_war (1 << 31)
^
>> lib/errseq.c:94:9: warning: converting the result of '<<' to a boolean always evaluates to true [-Wtautological-constant-compare]
arch/mips/include/asm/cmpxchg.h:204:7: note: expanded from macro 'cmpxchg'
if (!__SYNC_loongson3_war) \
^
arch/mips/include/asm/sync.h:147:34: note: expanded from macro '__SYNC_loongson3_war'
# define __SYNC_loongson3_war (1 << 31)
^
lib/errseq.c:200:4: warning: converting the result of '<<' to a boolean always evaluates to true [-Wtautological-constant-compare]
cmpxchg(eseq, old, new);
^
arch/mips/include/asm/cmpxchg.h:194:7: note: expanded from macro 'cmpxchg'
if (!__SYNC_loongson3_war) \
^
arch/mips/include/asm/sync.h:147:34: note: expanded from macro '__SYNC_loongson3_war'
# define __SYNC_loongson3_war (1 << 31)
^
lib/errseq.c:200:4: warning: converting the result of '<<' to a boolean always evaluates to true [-Wtautological-constant-compare]
arch/mips/include/asm/cmpxchg.h:204:7: note: expanded from macro 'cmpxchg'
if (!__SYNC_loongson3_war) \
^
arch/mips/include/asm/sync.h:147:34: note: expanded from macro '__SYNC_loongson3_war'
# define __SYNC_loongson3_war (1 << 31)
^
12 warnings generated.
Assembler messages:
Fatal error: invalid -march= option: `mips64r2'
clang-12: error: assembler command failed with exit code 1 (use -v to see invocation)
--
>> arch/mips/kernel/cmpxchg.c:44:12: warning: converting the result of '<<' to a boolean always evaluates to true [-Wtautological-constant-compare]
load32 = cmpxchg(ptr32, old32, new32);
^
arch/mips/include/asm/cmpxchg.h:194:7: note: expanded from macro 'cmpxchg'
if (!__SYNC_loongson3_war) \
^
arch/mips/include/asm/sync.h:147:34: note: expanded from macro '__SYNC_loongson3_war'
# define __SYNC_loongson3_war (1 << 31)
^
>> arch/mips/kernel/cmpxchg.c:44:12: warning: converting the result of '<<' to a boolean always evaluates to true [-Wtautological-constant-compare]
arch/mips/include/asm/cmpxchg.h:204:7: note: expanded from macro 'cmpxchg'
if (!__SYNC_loongson3_war) \
^
arch/mips/include/asm/sync.h:147:34: note: expanded from macro '__SYNC_loongson3_war'
# define __SYNC_loongson3_war (1 << 31)
^
arch/mips/kernel/cmpxchg.c:100:12: warning: converting the result of '<<' to a boolean always evaluates to true [-Wtautological-constant-compare]
load32 = cmpxchg(ptr32, old32, new32);
^
arch/mips/include/asm/cmpxchg.h:194:7: note: expanded from macro 'cmpxchg'
if (!__SYNC_loongson3_war) \
^
arch/mips/include/asm/sync.h:147:34: note: expanded from macro '__SYNC_loongson3_war'
# define __SYNC_loongson3_war (1 << 31)
^
arch/mips/kernel/cmpxchg.c:100:12: warning: converting the result of '<<' to a boolean always evaluates to true [-Wtautological-constant-compare]
arch/mips/include/asm/cmpxchg.h:204:7: note: expanded from macro 'cmpxchg'
if (!__SYNC_loongson3_war) \
^
arch/mips/include/asm/sync.h:147:34: note: expanded from macro '__SYNC_loongson3_war'
# define __SYNC_loongson3_war (1 << 31)
^
4 warnings generated.
Assembler messages:
Fatal error: invalid -march= option: `mips64r2'
clang-12: error: assembler command failed with exit code 1 (use -v to see invocation)


vim +33 lib/llist.c

f49f23abf3dd786d Huang Ying 2011-07-13 16
f49f23abf3dd786d Huang Ying 2011-07-13 17
f49f23abf3dd786d Huang Ying 2011-07-13 18 /**
f49f23abf3dd786d Huang Ying 2011-07-13 19 * llist_add_batch - add several linked entries in batch
f49f23abf3dd786d Huang Ying 2011-07-13 20 * @new_first: first entry in batch to be added
f49f23abf3dd786d Huang Ying 2011-07-13 21 * @new_last: last entry in batch to be added
f49f23abf3dd786d Huang Ying 2011-07-13 22 * @head: the head for your lock-less list
781f7fd916fc77a8 Huang Ying 2011-09-08 23 *
781f7fd916fc77a8 Huang Ying 2011-09-08 24 * Return whether list is empty before adding.
f49f23abf3dd786d Huang Ying 2011-07-13 25 */
781f7fd916fc77a8 Huang Ying 2011-09-08 26 bool llist_add_batch(struct llist_node *new_first, struct llist_node *new_last,
f49f23abf3dd786d Huang Ying 2011-07-13 27 struct llist_head *head)
f49f23abf3dd786d Huang Ying 2011-07-13 28 {
fb4214db50b00558 Oleg Nesterov 2013-07-08 29 struct llist_node *first;
f49f23abf3dd786d Huang Ying 2011-07-13 30
fb4214db50b00558 Oleg Nesterov 2013-07-08 31 do {
6aa7de059173a986 Mark Rutland 2017-10-23 32 new_last->next = first = READ_ONCE(head->first);
fb4214db50b00558 Oleg Nesterov 2013-07-08 @33 } while (cmpxchg(&head->first, first, new_first) != first);
781f7fd916fc77a8 Huang Ying 2011-09-08 34
fb4214db50b00558 Oleg Nesterov 2013-07-08 35 return !first;
f49f23abf3dd786d Huang Ying 2011-07-13 36 }
f49f23abf3dd786d Huang Ying 2011-07-13 37 EXPORT_SYMBOL_GPL(llist_add_batch);
f49f23abf3dd786d Huang Ying 2011-07-13 38

:::::: The code at line 33 was first introduced by commit
:::::: fb4214db50b00558cc6e274c88b3f7325068e942 llist: fix/simplify llist_add() and llist_add_batch()

:::::: TO: Oleg Nesterov <oleg@redhat.com>
:::::: CC: Al Viro <viro@zeniv.linux.org.uk>

---
0-DAY CI Kernel Test Service, Intel Corporation
https://lists.01.org/hyperkitty/list/kbuild-all@lists.01.org
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