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Posted to dev@brpc.apache.org by "chenBright (via GitHub)" <gi...@apache.org> on 2024/01/20 08:57:12 UTC
[PR] Support bthread_usleep to wait for Singleton in bthread (brpc)
chenBright opened a new pull request, #2517:
URL: https://github.com/apache/brpc/pull/2517
### What problem does this PR solve?
Issue Number:
Problem Summary:
对于::Singleton<T>，在T构造的时候，并发调用`get()`，只有一个线程会调用T的构造函数，其他线程会在`WaitForInstance`函数中等待（自旋+`sched_yield`）T完成构造。如果T构造函数中有挂起bthrea的操作，并发大的情况下，有可能会导致“死锁”问题：所有worker线程都在`WaitForInstance`函数中等待T完成构造，而此时已经没有worker可以调度执行T构造函数的bthread了，即T已经无法完成构造。
### What is changed and the side effects?
Changed:
在链接了bthread时，使用bthread_yield，这样在bthread上使用的:Singleton<T>就不会阻塞所有worker线程了。
Side effects:
- Performance effects(性能影响):
- Breaking backward compatibility(向后兼容性):
---
### Check List:
- Please make sure your changes are compilable(请确保你的更改可以通过编译).
- When providing us with a new feature, it is best to add related tests(如果你向我们增加一个新的功能, 请添加相关测试).
- Please follow [Contributor Covenant Code of Conduct](../../master/CODE_OF_CONDUCT.md).(请遵循贡献者准则).
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Re: [PR] Support bthread_usleep to wait for Singleton on bthread (brpc)
Posted by "chenBright (via GitHub)" <gi...@apache.org>.
chenBright commented on PR #2517:
URL: https://github.com/apache/brpc/pull/2517#issuecomment-1910054663
关闭该PR，因为可能会导致线程锁里调Singleton场景出现死锁问题。
有在构造函数中挂起协程操作的需求，可以使用 #2520 的特性。
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Re: [PR] Support bthread_yield to wait for Singleton in bthread (brpc)
Posted by "chenBright (via GitHub)" <gi...@apache.org>.
chenBright commented on code in PR #2517:
URL: https://github.com/apache/brpc/pull/2517#discussion_r1461769853
##########
src/butil/memory/singleton.cc:
##########
@@ -5,9 +5,23 @@
#include "butil/memory/singleton.h"
#include "butil/threading/platform_thread.h"
+__BEGIN_DECLS
+// Defined in bthread/bthread.cpp
+void BAIDU_WEAK bthread_yield();
+__END_DECLS
+
namespace butil {
namespace internal {
+void yield() {
+ if (bthread_yield) {
Review Comment:
或者自旋一定次数后，再调bthread_yield，这样可以自适应地防止死锁问题，不需要用户设置。因为很多时候，用户需要等到死锁了才会发现有bthread_yield的需求。可以自适应的话，可以完全规避这个问题。
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Re: [PR] Support bthread_yield to wait for Singleton in bthread (brpc)
Posted by "chenBright (via GitHub)" <gi...@apache.org>.
chenBright commented on code in PR #2517:
URL: https://github.com/apache/brpc/pull/2517#discussion_r1461769853
##########
src/butil/memory/singleton.cc:
##########
@@ -5,9 +5,23 @@
#include "butil/memory/singleton.h"
#include "butil/threading/platform_thread.h"
+__BEGIN_DECLS
+// Defined in bthread/bthread.cpp
+void BAIDU_WEAK bthread_yield();
+__END_DECLS
+
namespace butil {
namespace internal {
+void yield() {
+ if (bthread_yield) {
Review Comment:
或者自旋一定次数后，再调bthread_yield/bthread_usleep，这样可以自适应地防止死锁问题，不需要使用者设置。因为很多时候，使用者需要等到死锁了才会发现有bthread_yield的需求。可以自适应的话，可以完全规避这个问题。
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Re: [PR] Support bthread_yield to wait for Singleton in bthread (brpc)
Posted by "chenBright (via GitHub)" <gi...@apache.org>.
chenBright commented on code in PR #2517:
URL: https://github.com/apache/brpc/pull/2517#discussion_r1461769853
##########
src/butil/memory/singleton.cc:
##########
@@ -5,9 +5,23 @@
#include "butil/memory/singleton.h"
#include "butil/threading/platform_thread.h"
+__BEGIN_DECLS
+// Defined in bthread/bthread.cpp
+void BAIDU_WEAK bthread_yield();
+__END_DECLS
+
namespace butil {
namespace internal {
+void yield() {
+ if (bthread_yield) {
Review Comment:
或者自旋一定次数后，进入slow path（bthread_usleep 1ms），这样可以自适应地防止死锁问题，不需要使用者设置。因为很多时候，使用者需要等到死锁了才会发现有挂起协程的需求。可以自适应的话，可以完全规避这个问题。
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Re: [PR] Support bthread_yield to wait for Singleton in bthread (brpc)
Posted by "wwbmmm (via GitHub)" <gi...@apache.org>.
wwbmmm commented on PR #2517:
URL: https://github.com/apache/brpc/pull/2517#issuecomment-1905236057
LGTM
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Re: [PR] Support bthread_yield to wait for Singleton in bthread (brpc)
Posted by "chenBright (via GitHub)" <gi...@apache.org>.
chenBright commented on code in PR #2517:
URL: https://github.com/apache/brpc/pull/2517#discussion_r1461997899
##########
src/butil/memory/singleton.cc:
##########
@@ -5,9 +5,23 @@
#include "butil/memory/singleton.h"
#include "butil/threading/platform_thread.h"
+__BEGIN_DECLS
+// Defined in bthread/bthread.cpp
+void BAIDU_WEAK bthread_yield();
+__END_DECLS
+
namespace butil {
namespace internal {
+void yield() {
+ if (bthread_yield) {
Review Comment:
mutex/cond比bthread_usleep优雅，但是没有合适的位置初始化mutex/cond。
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Re: [PR] Support bthread_yield to wait for Singleton in bthread (brpc)
Posted by "wwbmmm (via GitHub)" <gi...@apache.org>.
wwbmmm commented on code in PR #2517:
URL: https://github.com/apache/brpc/pull/2517#discussion_r1461431437
##########
src/butil/memory/singleton.cc:
##########
@@ -5,9 +5,23 @@
#include "butil/memory/singleton.h"
#include "butil/threading/platform_thread.h"
+__BEGIN_DECLS
+// Defined in bthread/bthread.cpp
+void BAIDU_WEAK bthread_yield();
+__END_DECLS
+
namespace butil {
namespace internal {
+void yield() {
+ if (bthread_yield) {
Review Comment:
是不是加个开关控制一下？毕竟大部分Singleton场景，是不需要bthread_yield的
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Re: [PR] Support bthread_usleep to wait for Singleton on bthread (brpc)
Posted by "chenBright (via GitHub)" <gi...@apache.org>.
chenBright closed pull request #2517: Support bthread_usleep to wait for Singleton on bthread
URL: https://github.com/apache/brpc/pull/2517
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Re: [PR] Support bthread_yield to wait for Singleton in bthread (brpc)
Posted by "chenBright (via GitHub)" <gi...@apache.org>.
chenBright commented on code in PR #2517:
URL: https://github.com/apache/brpc/pull/2517#discussion_r1461474105
##########
src/butil/memory/singleton.cc:
##########
@@ -5,9 +5,23 @@
#include "butil/memory/singleton.h"
#include "butil/threading/platform_thread.h"
+__BEGIN_DECLS
+// Defined in bthread/bthread.cpp
+void BAIDU_WEAK bthread_yield();
+__END_DECLS
+
namespace butil {
namespace internal {
+void yield() {
+ if (bthread_yield) {
Review Comment:
Singleton加个模板参数，控制是否使用bthread_yield，默认值为false，如何？
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Re: [PR] Support bthread_yield to wait for Singleton in bthread (brpc)
Posted by "chenBright (via GitHub)" <gi...@apache.org>.
chenBright commented on code in PR #2517:
URL: https://github.com/apache/brpc/pull/2517#discussion_r1461769853
##########
src/butil/memory/singleton.cc:
##########
@@ -5,9 +5,23 @@
#include "butil/memory/singleton.h"
#include "butil/threading/platform_thread.h"
+__BEGIN_DECLS
+// Defined in bthread/bthread.cpp
+void BAIDU_WEAK bthread_yield();
+__END_DECLS
+
namespace butil {
namespace internal {
+void yield() {
+ if (bthread_yield) {
Review Comment:
或者自旋一定次数后，再调bthread_usleep，这样可以自适应地防止死锁问题，不需要使用者设置。因为很多时候，使用者需要等到死锁了才会发现有挂起协程的需求。可以自适应的话，可以完全规避这个问题。
--
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Re: [PR] Support bthread_yield to wait for Singleton in bthread (brpc)
Posted by "chenBright (via GitHub)" <gi...@apache.org>.
chenBright commented on code in PR #2517:
URL: https://github.com/apache/brpc/pull/2517#discussion_r1461769853
##########
src/butil/memory/singleton.cc:
##########
@@ -5,9 +5,23 @@
#include "butil/memory/singleton.h"
#include "butil/threading/platform_thread.h"
+__BEGIN_DECLS
+// Defined in bthread/bthread.cpp
+void BAIDU_WEAK bthread_yield();
+__END_DECLS
+
namespace butil {
namespace internal {
+void yield() {
+ if (bthread_yield) {
Review Comment:
或者自旋一定次数后，再调bthread_yield/bthread_usleep，这样可以自适应地防止死锁问题，不需要用户设置。因为很多时候，用户需要等到死锁了才会发现有bthread_yield的需求。可以自适应的话，可以完全规避这个问题。
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