【标题描述】:
并发改config文件导致coredump

【测试类型：并发】【测试版本：3.0.0】
【操作系统和硬件信息】(查询命令: cat /etc/system-release, uname -a):
CentOS Linux release 7.9.2009 (Core)
x86_64 GNU/Linux

【测试环境】(单机/1主x备x级联备):
单机

【被测功能】:
多线程并发使用ALTER SYSTEM SET命令修改postgresql.conf文件

【数据库版本】(查询命令: gaussdb –V):
openGauss 3.0.0 build 6c589864

【预置条件】:
启动opengauss

【操作步骤】(请填写详细的操作步骤):

1. 启动opengauss
2. 使用yat并发跑一组testcases, 每个testcase使用ALTER SYSTEM SET命令修改不同的config参数
   e.g.
   testcase1:
   -- @testpoint: 使用 alter system set 设置guc变量后检查是否设置成功
   ALTER SYSTEM SET archive_mode to on;
   SQL SUCCESS
   select pg_sleep(2);
   +----------+
   | pg_sleep |
   +----------+
   | |
   +----------+
   show archive_mode;
   +--------------+
   | archive_mode |
   +--------------+
   | on |
   +--------------+
   ALTER SYSTEM SET archive_mode to off;
   SQL SUCCESS
   select pg_sleep(2);
   +----------+
   | pg_sleep |
   +----------+
   | |
   +----------+
   show archive_mode;
   +--------------+
   | archive_mode |
   +--------------+
   | off |
   +--------------+
   testcase2:
   -- @testpoint: 使用 alter system set 设置guc变量后检查是否设置成功
   ALTER SYSTEM SET archive_timeout to 600;
   SQL SUCCESS
   select pg_sleep(2);
   +----------+
   | pg_sleep |
   +----------+
   | |
   +----------+
   show archive_timeout;
   +-----------------+
   | archive_timeout |
   +-----------------+
   | 10min |
   +-----------------+
   ALTER SYSTEM SET archive_timeout to 0;
   SQL SUCCESS
   select pg_sleep(2);
   +----------+
   | pg_sleep |
   +----------+
   | |
   +----------+
   show archive_timeout;
   +-----------------+
   | archive_timeout |
   +-----------------+
   | 0 |
   +-----------------+

【预期输出】:
每个testcase修改参数后，postgresql.conf文件中所有修改了的参数结果一致。以以上两个testcase为例，archive_mode应为off, archive_timeout应为0.

【实际输出】:
数据库运行出错，coredump

【原因分析】:

1. 这个问题的根因
   多线程同时更改postgresql.conf文件时，锁为flock()，是process级别的锁，所以opengauss的其中一个线程拿到锁后，所有opengauss线程都获得锁，实际没有起到多线程保护作用。

关于修改conf文件有两种race condition，一种是thread, opengauss不同thread会同时修改conf文件；另一种是process，gs_guc程序和opengauss主程序会同时修改conf文件。

2. 问题解决方案

保留原先的flock锁作为process锁，然后在这基础上加上opengauss全局锁lwlock作为thread锁，每次更改conf文件都需要拿到这两把锁，release的时候需要先release process锁，再release thread锁，不然会有race condition

【日志信息】(请附上日志文件、截图、coredump信息):
#0 write_guc_file (
    path=path@entry=0x7f21f6f6c020 "/data/msun/openGauss-server/src/test/regress/tmp_check/datanode1/postgresql.conf.bak_bak", lines=lines@entry=0x0) at guc.cpp:12027
#1 0x000055cd7c38e4a9 in WriteAlterSystemSetGucFile (
    ConfFileName=ConfFileName@entry=0x7f21f6f6c020 "/data/msun/openGauss-server/src/test/regress/tmp_check/datanode1/postgresql.conf.bak_bak", opt_lines=0x0, filelock=filelock@entry=0x7f21f6f6b780)
    at guc.cpp:8507
#2 0x000055cd7c38ea14 in AlterSystemSetConfigFile (altersysstmt=altersysstmt@entry=0x7f21fb7f1890)
    at guc.cpp:8596
#3 0x000055cd7c8d04fd in standard_ProcessUtility (parse_tree=parse_tree@entry=0x7f21fb7f1890,
    query_string=query_string@entry=0x7f21f744d790 "alter system set autovacuum to off",
    params=params@entry=0x0, is_top_level=,
    dest=dest@entry=0x55cd8258bca0 , sent_to_remote=,
    completion_tag=0x7f21f6f6f120 "", isCTAS=false) at utility.cpp:5557
#4 0x00007f22d7f590a9 in gsaudit_ProcessUtility_hook (parsetree=0x7f21fb7f1890,
    queryString=0x7f21f744d790 "alter system set autovacuum to off", params=0x0,
    isTopLevel=, dest=0x55cd8258bca0 , sentToRemote=,
    completionTag=0x7f21f6f6f120 "", isCTAS=false) at gs_policy_plugin.cpp:1062
#5 0x000055cd7c8de63c in pgaudit_ProcessUtility (parsetree=0x7f21fb7f1890,
    queryString=0x7f21f744d790 "alter system set autovacuum to off", params=,
    isTopLevel=, dest=, sentToRemote=,
    completionTag=0x7f21f6f6f120 "", isCTAS=false) at auditfuncs.cpp:1198
#6 0x000055cd7c8c2265 in PortalRunUtility (portal=portal@entry=0x7f224e0bc040,
    utilityStmt=utilityStmt@entry=0x7f21fb7f1890, isTopLevel=isTopLevel@entry=true,
    dest=dest@entry=0x55cd8258bca0 ,
    completionTag=completionTag@entry=0x7f21f6f6f120 "") at pquery.cpp:1758
#7 0x000055cd7c8c33c4 in PortalRunMulti (portal=portal@entry=0x7f224e0bc040,
    isTopLevel=isTopLevel@entry=true, dest=0x55cd8258bca0 , dest@entry=0x7f223a1c64a0,
    altdest=0x55cd8258bca0 , altdest@entry=0x7f223a1c64a0,
    completionTag=completionTag@entry=0x7f21f6f6f120 "") at pquery.cpp:1937
#8 0x000055cd7c8c5f48 in PortalRun (portal=portal@entry=0x7f224e0bc040,
    count=count@entry=9223372036854775807, isTopLevel=isTopLevel@entry=true,
    dest=dest@entry=0x7f223a1c64a0, altdest=altdest@entry=0x7f223a1c64a0,
    completionTag=completionTag@entry=0x7f21f6f6f120 "") at pquery.cpp:1183
#9 0x000055cd7be74890 in exec_execute_message (portal_name=portal_name@entry=0x7f223a1c6040 "",
    max_rows=9223372036854775807, max_rows@entry=0) at postgres.cpp:4997
#10 0x000055cd7c8c045a in PostgresMain (argc=, argv=argv@entry=0x7f2244af1780,
    dbname=, username=) at postgres.cpp:8784
#11 0x000055cd7c832c6b in BackendRun (port=port@entry=0x7f21f6f6f7b0) at postmaster.cpp:7746
#12 0x000055cd7c8508e8 in GaussDbThreadMain<(knl_thread_role)2> (arg=0x7f226aadbf98)
    at postmaster.cpp:11629
#13 0x000055cd7c832cc5 in InternalThreadFunc (args=) at postmaster.cpp:12186
---Type to continue, or q to quit---
#14 0x00007f22e24a1ea5 in start_thread () from /lib64/libpthread.so.0
#15 0x00007f22e21cab0d in clone () from /lib64/libc.so.6