Re: fs/io_uring.c:10086:24: warning: Value stored to 'sqe' during its initialization is never read [clang-analyzer-deadcode.DeadStores]

From: kernel test robot
Date: Fri Nov 05 2021 - 02:42:33 EST

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tree: config: arm-randconfig-c002-20211031 compiler: clang version 14.0.0 ( wget # install # apt-get # If you fix the issue, Reported-by: kernel

clang-analyzer warnings:
>> fs/io_uring.c:10086:24:

vim +/sqe +10086 fs/io_uring.c

87ce955b24c994 Jens Axboe c072481ded14bc Pavel Begunkov c072481ded14bc Pavel Begunkov 87ce955b24c994 Jens Axboe dbbe9c642411c3 Joseph Qi 83f84356bc8f2d Hao Xu 83f84356bc8f2d Hao Xu 83f84356bc8f2d Hao Xu 83f84356bc8f2d Hao Xu 83f84356bc8f2d Hao Xu 83f84356bc8f2d Hao Xu 83f84356bc8f2d Hao Xu f75d118349be05 Jens Axboe fad8e0de4426a7 Jens Axboe 83f84356bc8f2d Hao Xu 83f84356bc8f2d Hao Xu 83f84356bc8f2d Hao Xu 83f84356bc8f2d Hao Xu 83f84356bc8f2d Hao Xu 83f84356bc8f2d Hao Xu 83f84356bc8f2d Hao Xu 83f84356bc8f2d Hao Xu f75d118349be05 Jens Axboe f75d118349be05 Jens Axboe f75d118349be05 Jens Axboe f75d118349be05 Jens Axboe f75d118349be05 Jens Axboe f75d118349be05 Jens Axboe f75d118349be05 Jens Axboe f75d118349be05 Jens Axboe f75d118349be05 Jens Axboe f75d118349be05 Jens Axboe f75d118349be05 Jens Axboe f75d118349be05 Jens Axboe f75d118349be05 Jens Axboe 83f84356bc8f2d Hao Xu 83f84356bc8f2d Hao Xu f75d118349be05 Jens Axboe f75d118349be05 Jens Axboe f75d118349be05 Jens Axboe 83f84356bc8f2d Hao Xu f75d118349be05 Jens Axboe f75d118349be05 Jens Axboe 83f84356bc8f2d Hao Xu f75d118349be05 Jens Axboe f75d118349be05 Jens Axboe f75d118349be05 Jens Axboe f75d118349be05 Jens Axboe f75d118349be05 Jens Axboe 83f84356bc8f2d Hao Xu 83f84356bc8f2d Hao Xu f75d118349be05 Jens Axboe f75d118349be05 Jens Axboe 83f84356bc8f2d Hao Xu 87ce955b24c994 Jens Axboe fad8e0de4426a7 Jens Axboe fad8e0de4426a7 Jens Axboe fad8e0de4426a7 Jens Axboe fad8e0de4426a7 Jens Axboe fad8e0de4426a7 Jens Axboe fad8e0de4426a7 Jens Axboe fad8e0de4426a7 Jens Axboe fad8e0de4426a7 Jens Axboe 5f3f26f98ae484 Jens Axboe dbbe9c642411c3 Joseph Qi 5f3f26f98ae484 Jens Axboe 5f3f26f98ae484 Jens Axboe 5f3f26f98ae484 Jens Axboe dbbe9c642411c3 Joseph Qi dbbe9c642411c3 Joseph Qi dbbe9c642411c3 Joseph Qi 87ce955b24c994 Jens Axboe fad8e0de4426a7 Jens Axboe 7b29f92da377c3 Jens Axboe 87ce955b24c994 Jens Axboe 87ce955b24c994 Jens Axboe 87ce955b24c994 Jens Axboe 87ce955b24c994 Jens Axboe 87ce955b24c994 Jens Axboe 87ce955b24c994 Jens Axboe 87ce955b24c994 Jens Axboe fad8e0de4426a7 Jens Axboe 41edf1a5ec967b Pavel Begunkov 4751f53d74a688 Pavel Begunkov 87ce955b24c994 Jens Axboe 4751f53d74a688 Pavel Begunkov 87ce955b24c994 Jens Axboe 61cf93700fe635 Matthew Wilcox (Oracle 61cf93700fe635 Matthew Wilcox (Oracle 61cf93700fe635 Matthew Wilcox (Oracle 61cf93700fe635 Matthew Wilcox (Oracle 87ce955b24c994 Jens Axboe 61cf93700fe635 Matthew Wilcox (Oracle 61cf93700fe635 Matthew Wilcox (Oracle 87ce955b24c994 Jens Axboe 83f84356bc8f2d Hao Xu 83f84356bc8f2d Hao Xu 83f84356bc8f2d Hao Xu 83f84356bc8f2d Hao Xu 79ebeaee8a21a0 Jens Axboe d7718a9d25a614 Jens Axboe d7718a9d25a614 Jens Axboe d7718a9d25a614 Jens Axboe d7718a9d25a614 Jens Axboe d7718a9d25a614 Jens Axboe d7718a9d25a614 Jens Axboe d7718a9d25a614 Jens Axboe d7718a9d25a614 Jens Axboe 83f84356bc8f2d Hao Xu 83f84356bc8f2d Hao Xu 83f84356bc8f2d Hao Xu 83f84356bc8f2d Hao Xu 83f84356bc8f2d Hao Xu 83f84356bc8f2d Hao Xu 83f84356bc8f2d Hao Xu 83f84356bc8f2d Hao Xu 83f84356bc8f2d Hao Xu 83f84356bc8f2d Hao Xu 79ebeaee8a21a0 Jens Axboe 87ce955b24c994 Jens Axboe 87ce955b24c994 Jens Axboe
:::::: The code :::::: 83f84356bc8f2dda9d
:::::: TO: Hao Xu :::::: CC: Jens
---
0-DAY CI Kernel Description: application/gzip message: Greg KH: "Re: [RESEND PATCH v2] thermal: Fix a NULL pointer dereference" message: kernel test robot: "[fs] a0918006f9: netperf.Throughput_tps -11.6% regression" in thread: Jens Axboe: "Re: fs/io_uring.c:10086:24: warning: Value stored to 'sqe' during its initialization is never read [clang-analyzer-deadcode.DeadStores]" sorted by: [ date ] [ thread ] [ subject ] [ author ] href="https://git.kernel.org/pub/scm/linux/kernel/git/torvalds/linux.git">https://git.kernel.org/pub/scm/linux/kernel/git/torvalds/linux.git master
1eaf0197db8e6b3e197d5c7
7407b4ba4ceb98e6437e472 io_uring: harder fdinfo sq/cq ring iterating
(attached as .config)
rel="nofollow" href="https://github.com/llvm/llvm-project">https://github.com/llvm/llvm-project 82ed106567063ea269c6d5669278b733e173a42f)
rel="nofollow" href="https://raw.githubusercontent.com/intel/lkp-tests/master/sbin/make.cross">https://raw.githubusercontent.com/intel/lkp-tests/master/sbin/make.cross -O ~/bin/make.cross
arm cross compiling tool for clang build
install binutils-arm-linux-gnueabi
href="https://git.kernel.org/pub/scm/linux/kernel/git/torvalds/linux.git/commit/?id=f75d118349be055d47407b4ba4ceb98e6437e472">https://git.kernel.org/pub/scm/linux/kernel/git/torvalds/linux.git/commit/?id=f75d118349be055d47407b4ba4ceb98e6437e472
rel="nofollow" href="https://git.kernel.org/pub/scm/linux/kernel/git/torvalds/linux.git">https://git.kernel.org/pub/scm/linux/kernel/git/torvalds/linux.git
--no-tags linus master
f75d118349be055d47407b4ba4ceb98e6437e472
attached .config to linux build tree
PATH=$HOME/0day COMPILER=clang make.cross ARCH=arm clang-analyzer
kindly add following tag as appropriate
test robot <lkp@xxxxxxxxx>
(new ones prefixed by >>)
warning: Value stored to 'sqe' during its initialization is never read [clang-analyzer-deadcode.DeadStores]
struct io_uring_sqe *sqe = &ctx->sq_sqes[sq_idx];
^~~ ~~~~~~~~~~~~~~~~~~~~~
2020-01-30 10051
2021-10-04 10052 static __cold void __io_uring_show_fdinfo(struct io_ring_ctx *ctx,
2021-10-04 10053 struct seq_file *m)
2020-01-30 10054 {
2020-09-29 10055 struct io_sq_data *sq = NULL;
2021-09-13 10056 struct io_overflow_cqe *ocqe;
2021-09-13 10057 struct io_rings *r = ctx->rings;
2021-09-13 10058 unsigned int sq_mask = ctx->sq_entries - 1, cq_mask = ctx->cq_entries - 1;
2021-09-13 10059 unsigned int sq_head = READ_ONCE(r->sq.head);
2021-09-13 10060 unsigned int sq_tail = READ_ONCE(r->sq.tail);
2021-09-13 10061 unsigned int cq_head = READ_ONCE(r->cq.head);
2021-09-13 10062 unsigned int cq_tail = READ_ONCE(r->cq.tail);
2021-10-29 10063 unsigned int sq_entries, cq_entries;
2020-09-28 10064 bool has_lock;
2021-09-13 10065 unsigned int i;
2021-09-13 10066
2021-09-13 10067 /*
2021-09-13 10068 * we may get imprecise sqe and cqe info if uring is actively running
2021-09-13 10069 * since we get cached_sq_head and cached_cq_tail without uring_lock
2021-09-13 10070 * and sq_tail and cq_head are changed by userspace. But it's ok since
2021-09-13 10071 * we usually use these info when it is stuck.
2021-09-13 10072 */
2021-10-29 10073 seq_printf(m, "SqMask:\t\t0x%x\n", sq_mask);
2021-10-29 10074 seq_printf(m, "SqHead:\t%u\n", sq_head);
2021-10-29 10075 seq_printf(m, "SqTail:\t%u\n", sq_tail);
2021-10-29 10076 seq_printf(m, "CachedSqHead:\t%u\n", ctx->cached_sq_head);
2021-10-29 10077 seq_printf(m, "CqMask:\t0x%x\n", cq_mask);
2021-10-29 10078 seq_printf(m, "CqHead:\t%u\n", cq_head);
2021-10-29 10079 seq_printf(m, "CqTail:\t%u\n", cq_tail);
2021-10-29 10080 seq_printf(m, "CachedCqTail:\t%u\n", ctx->cached_cq_tail);
2021-10-29 10081 seq_printf(m, "SQEs:\t%u\n", sq_tail - ctx->cached_sq_head);
2021-10-29 10082 sq_entries = min(sq_tail - sq_head, ctx->sq_entries);
2021-10-29 10083 for (i = 0; i < sq_entries; i++) {
2021-10-29 10084 unsigned int entry = i + sq_head;
2021-10-29 10085 unsigned int sq_idx = READ_ONCE(ctx->sq_array[entry & sq_mask]);
2021-09-13 @10086 struct io_uring_sqe *sqe = &ctx->sq_sqes[sq_idx];
2021-09-13 10087
2021-10-29 10088 if (sq_idx > sq_mask)
2021-10-29 10089 continue;
2021-10-29 10090 sqe = &ctx->sq_sqes[sq_idx];
2021-09-13 10091 seq_printf(m, "%5u: opcode:%d, fd:%d, flags:%x, user_data:%llu\n",
2021-10-29 10092 sq_idx, sqe->opcode, sqe->fd, sqe->flags,
2021-10-29 10093 sqe->user_data);
2021-09-13 10094 }
2021-10-29 10095 seq_printf(m, "CQEs:\t%u\n", cq_tail - cq_head);
2021-10-29 10096 cq_entries = min(cq_tail - cq_head, ctx->cq_entries);
2021-10-29 10097 for (i = 0; i < cq_entries; i++) {
2021-10-29 10098 unsigned int entry = i + cq_head;
2021-10-29 10099 struct io_uring_cqe *cqe = &r->cqes[entry & cq_mask];
2021-09-13 10100
2021-09-13 10101 seq_printf(m, "%5u: user_data:%llu, res:%d, flag:%x\n",
2021-10-29 10102 entry & cq_mask, cqe->user_data, cqe->res,
2021-10-29 10103 cqe->flags);
2021-09-13 10104 }
2020-01-30 10105
2020-09-28 10106 /*
2020-09-28 10107 * Avoid ABBA deadlock between the seq lock and the io_uring mutex,
2020-09-28 10108 * since fdinfo case grabs it in the opposite direction of normal use
2020-09-28 10109 * cases. If we fail to get the lock, we just don't iterate any
2020-09-28 10110 * structures that could be going away outside the io_uring mutex.
2020-09-28 10111 */
2020-09-28 10112 has_lock = mutex_trylock(&ctx->uring_lock);
2020-09-28 10113
2021-02-25 10114 if (has_lock && (ctx->flags & IORING_SETUP_SQPOLL)) {
2020-09-29 10115 sq = ctx->sq_data;
2021-02-25 10116 if (!sq->thread)
2021-02-25 10117 sq = NULL;
2021-02-25 10118 }
2020-09-29 10119
2020-09-29 10120 seq_printf(m, "SqThread:\t%d\n", sq ? task_pid_nr(sq->thread) : -1);
2020-09-29 10121 seq_printf(m, "SqThreadCpu:\t%d\n", sq ? task_cpu(sq->thread) : -1);
2020-01-30 10122 seq_printf(m, "UserFiles:\t%u\n", ctx->nr_user_files);
2020-09-28 10123 for (i = 0; has_lock && i < ctx->nr_user_files; i++) {
2021-03-12 10124 struct file *f = io_file_from_index(ctx, i);
2020-01-30 10125
2020-01-30 10126 if (f)
2020-01-30 10127 seq_printf(m, "%5u: %s\n", i, file_dentry(f)->d_iname);
2020-01-30 10128 else
2020-01-30 10129 seq_printf(m, "%5u: <none>\n", i);
2020-01-30 10130 }
2020-01-30 10131 seq_printf(m, "UserBufs:\t%u\n", ctx->nr_user_bufs);
2020-09-28 10132 for (i = 0; has_lock && i < ctx->nr_user_bufs; i++) {
2021-04-25 10133 struct io_mapped_ubuf *buf = ctx->user_bufs[i];
2021-04-01 10134 unsigned int len = buf->ubuf_end - buf->ubuf;
2020-01-30 10135
2021-04-01 10136 seq_printf(m, "%5u: 0x%llx/%u\n", i, buf->ubuf, len);
2020-01-30 10137 }
2021-03-08 10138) if (has_lock && !xa_empty(&ctx->personalities)) {
2021-03-08 10139) unsigned long index;
2021-03-08 10140) const struct cred *cred;
2021-03-08 10141)
2020-01-30 10142 seq_printf(m, "Personalities:\n");
2021-03-08 10143) xa_for_each(&ctx->personalities, index, cred)
2021-03-08 10144) io_uring_show_cred(m, index, cred);
2020-01-30 10145 }
2021-09-13 10146 if (has_lock)
2021-09-13 10147 mutex_unlock(&ctx->uring_lock);
2021-09-13 10148
2021-09-13 10149 seq_puts(m, "PollList:\n");
2021-08-10 10150 spin_lock(&ctx->completion_lock);
2020-02-14 10151 for (i = 0; i < (1U << ctx->cancel_hash_bits); i++) {
2020-02-14 10152 struct hlist_head *list = &ctx->cancel_hash[i];
2020-02-14 10153 struct io_kiocb *req;
2020-02-14 10154
2020-02-14 10155 hlist_for_each_entry(req, list, hash_node)
2020-02-14 10156 seq_printf(m, " op=%d, task_works=%d\n", req->opcode,
2020-02-14 10157 req->task->task_works != NULL);
2020-02-14 10158 }
2021-09-13 10159
2021-09-13 10160 seq_puts(m, "CqOverflowList:\n");
2021-09-13 10161 list_for_each_entry(ocqe, &ctx->cq_overflow_list, list) {
2021-09-13 10162 struct io_uring_cqe *cqe = &ocqe->cqe;
2021-09-13 10163
2021-09-13 10164 seq_printf(m, " user_data=%llu, res=%d, flags=%x\n",
2021-09-13 10165 cqe->user_data, cqe->res, cqe->flags);
2021-09-13 10166
2021-09-13 10167 }
2021-09-13 10168
2021-08-10 10169 spin_unlock(&ctx->completion_lock);
2020-01-30 10170 }
2020-01-30 10171
at line 10086 was first introduced by commit
0c9c7edb94decf71a36d26 io_uring: add more uring info to fdinfo for debug
<haoxu@xxxxxxxxxxxxxxxxx>
Axboe <axboe@xxxxxxxxx>
Test Service, Intel Corporation
href="https://lists.01.org/hyperkitty/list/kbuild-all@xxxxxxxxxxxx">https://lists.01.org/hyperkitty/list/kbuild-all@xxxxxxxxxxxx

Attachment: >.config.gz

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