MySQL 5.5 版本，事物中因为 S 锁，导致后续 update 语句出现死锁，请大佬帮我分析一下

场景：有一个提交订单的操作，在事物执行过程中库存表被操作两次，第一次是 select 语句，第二次是 update，在执行过程中出现了死锁。#

事物中包含这个表的操作的两处代码如下：

第一处#

第二处#

两处代码中有一些判断库存是否足够的逻辑

在并发中出现了死锁的情况，死锁日志附在最后。
因为死锁日志中说有一个事物拥有 S 锁，但是我并没有在事物的任何地方用 lock in share mode 加锁，有点想不通，google 上也没有找到有价值的资料，我所了解到的 select 除非显示指定加锁，否则不会任何锁到查询结果上，那么这个 S 锁是怎么来的呢？

附录：

1. show engine InnoDB status 的结果

   =====================================
   200107 20:50:08 INNODB MONITOR OUTPUT
   =====================================
   Per second averages calculated from the last 2 seconds
   -----------------
   BACKGROUND THREAD
   -----------------
   srv_master_thread loops: 1075284 1_second, 1075284 sleeps, 94343 10_second, 139601 background, 139597 flush
   srv_master_thread log flush and writes: 1076095
   ----------
   SEMAPHORES
   ----------
   OS WAIT ARRAY INFO: reservation count 291167, signal count 282874
   Mutex spin waits 186869, rounds 5618225, OS waits 168869
   RW-shared spins 99472, rounds 2984074, OS waits 69671
   RW-excl spins 19063, rounds 1577971, OS waits 47999
   Spin rounds per wait: 30.07 mutex, 30.00 RW-shared, 82.78 RW-excl
   ------------------------
   LATEST DETECTED DEADLOCK
   ------------------------
   200107 11:55:08
   *** (1) TRANSACTION:
   TRANSACTION BA9158, ACTIVE 0 sec starting index read
   mysql tables in use 1, locked 1
   LOCK WAIT 25 lock struct(s), heap size 3112, 47 row lock(s)
   MySQL thread id 285444, OS thread handle 0x7f34240cf700, query id 12333484 *.*.*.* root Updating
   update t_inventory
               set out_count = convert(1748.000000, decimal(19, 0)), out_price = 16.933352, out_money = 29599.500000,
                   balance_count = convert(380.000000, decimal(19, 0)), balance_money = 6270.000000
               where warehouse_id = '9BC7C41D-B5C1-11E9-ACCF-00163E02BF40' and goods_id = '11338'
   *** (1) WAITING FOR THIS LOCK TO BE GRANTED:
   RECORD LOCKS space id 0 page no 18850 n bits 800 index `t_inventory_goods_id_index` of table `cod_erp`.`t_inventory` trx id BA9158 lock_mode X waiting
   Record lock, heap no 459 PHYSICAL RECORD: n_fields 2; compact format; info bits 0
    0: len 5; hex 3131333338; asc 11338;;
    1: len 8; hex 8000000000000cac; asc         ;;
   
   *** (2) TRANSACTION:
   TRANSACTION BA915B, ACTIVE 0 sec starting index read
   mysql tables in use 1, locked 1
   25 lock struct(s), heap size 3112, 47 row lock(s)
   MySQL thread id 285438, OS thread handle 0x7f3418c0e700, query id 12333485 *.*.*.* root Updating
   update t_inventory
               set out_count = convert(1748.000000, decimal(19, 0)), out_price = 16.933352, out_money = 29599.500000,
                   balance_count = convert(380.000000, decimal(19, 0)), balance_money = 6270.000000
               where warehouse_id = '9BC7C41D-B5C1-11E9-ACCF-00163E02BF40' and goods_id = '11338'
   *** (2) HOLDS THE LOCK(S):
   RECORD LOCKS space id 0 page no 18850 n bits 800 index `t_inventory_goods_id_index` of table `cod_erp`.`t_inventory` trx id BA915B lock mode S
   Record lock, heap no 459 PHYSICAL RECORD: n_fields 2; compact format; info bits 0
    0: len 5; hex 3131333338; asc 11338;;
    1: len 8; hex 8000000000000cac; asc         ;;
   
   *** (2) WAITING FOR THIS LOCK TO BE GRANTED:
   RECORD LOCKS space id 0 page no 18850 n bits 800 index `t_inventory_goods_id_index` of table `cod_erp`.`t_inventory` trx id BA915B lock_mode X waiting
   Record lock, heap no 459 PHYSICAL RECORD: n_fields 2; compact format; info bits 0
    0: len 5; hex 3131333338; asc 11338;;
    1: len 8; hex 8000000000000cac; asc         ;;
   
   *** WE ROLL BACK TRANSACTION (2)
   ------------
   TRANSACTIONS
   ------------
   Trx id counter BB6AD9
   Purge done for trx's n:o < BB6ACB undo n:o < 0
   History list length 1252
   LIST OF TRANSACTIONS FOR EACH SESSION:
   ---TRANSACTION 0, not started
   MySQL thread id 293700, OS thread handle 0x7f3424192700, query id 12702737 *.*.*.* root
   ---TRANSACTION 0, not started
   MySQL thread id 293699, OS thread handle 0x7f34240cf700, query id 12702824 *.*.*.* root
   ---TRANSACTION BB6AD1, not started
   MySQL thread id 293698, OS thread handle 0x7f34156c2700, query id 12702908 *.*.*.* root
   show ENGINE INNODB status
   --------
   FILE I/O
   --------
   I/O thread 0 state: waiting for i/o request (insert buffer thread)
   I/O thread 1 state: waiting for i/o request (log thread)
   I/O thread 2 state: waiting for i/o request (read thread)
   I/O thread 3 state: waiting for i/o request (read thread)
   I/O thread 4 state: waiting for i/o request (read thread)
   I/O thread 5 state: waiting for i/o request (read thread)
   I/O thread 6 state: waiting for i/o request (write thread)
   I/O thread 7 state: waiting for i/o request (write thread)
   I/O thread 8 state: waiting for i/o request (write thread)
   I/O thread 9 state: waiting for i/o request (write thread)
   Pending normal aio reads: 0 [0, 0, 0, 0] , aio writes: 0 [0, 0, 0, 0] ,
    ibuf aio reads: 0, log i/o's: 0, sync i/o's: 0
   Pending flushes (fsync) log: 0; buffer pool: 0
   254575643 OS file reads, 2626664 OS file writes, 1560458 OS fsyncs
   0.00 reads/s, 0 avg bytes/read, 0.00 writes/s, 0.00 fsyncs/s
   -------------------------------------
   INSERT BUFFER AND ADAPTIVE HASH INDEX
   -------------------------------------
   Ibuf: size 1, free list len 12, seg size 14, 218732 merges
   merged operations:
    insert 453566, delete mark 1980934, delete 2352
   discarded operations:
    insert 0, delete mark 0, delete 0
   Hash table size 34679, node heap has 22 buffer(s)
   0.00 hash searches/s, 0.00 non-hash searches/s
   ---
   LOG
   ---
   Log sequence number 14929779885
   Log flushed up to   14929779885
   Last checkpoint at  14929779885
   0 pending log writes, 0 pending chkp writes
   1414978 log i/o's done, 0.00 log i/o's/second
   ----------------------
   BUFFER POOL AND MEMORY
   ----------------------
   Total memory allocated 17170432; in additional pool allocated 0
   Dictionary memory allocated 1070678
   Buffer pool size   1024
   Free buffers       1
   Database pages     1001
   Old database pages 349
   Modified db pages  0
   Pending reads 0
   Pending writes: LRU 0, flush list 0, single page 0
   Pages made young 348119979, not young 0
   0.00 youngs/s, 0.00 non-youngs/s
   Pages read 340194818, created 67746, written 1560724
   0.00 reads/s, 0.00 creates/s, 0.00 writes/s
   No buffer pool page gets since the last printout
   Pages read ahead 0.00/s, evicted without access 0.00/s, Random read ahead 0.00/s
   LRU len: 1001, unzip_LRU len: 0
   I/O sum[5075]:cur[0], unzip sum[0]:cur[0]
   --------------
   ROW OPERATIONS
   --------------
   0 queries inside InnoDB, 0 queries in queue
   1 read views open inside InnoDB
   Main thread process no. 2731, id 139861685458688, state: waiting for server activity
   Number of rows inserted 5273253, updated 6312884, deleted 4865078, read 17337326011
   0.00 inserts/s, 0.00 updates/s, 0.00 deletes/s, 0.00 reads/s
   ----------------------------
   END OF INNODB MONITOR OUTPUT
   ============================Copy

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