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Posted to dev@brpc.apache.org by GitBox <gi...@apache.org> on 2020/08/07 09:26:42 UTC
[GitHub] [incubator-brpc] bengol opened a new pull request #1200: reduce sampler's mutex scope
bengol opened a new pull request #1200:
URL: https://github.com/apache/incubator-brpc/pull/1200
Change-Id: I7e413acedc8dfb93eae5c08243f0ff3e484f7059
问题: 线上环境中，进程退出时，hang在sampler->destroy()中的_mutex lock上，持有该_mutex的线程已经不再使用该锁且在正常运行，没有分析出发生路径
改动原因: _used变量无需_mutex保护，减少_mutex的范围来规避该问题。同时stop变量跨越了线程，需要atomic
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[GitHub] [incubator-brpc] bengol commented on pull request #1200: reduce sampler's mutex scope
Posted by GitBox <gi...@apache.org>.
bengol commented on pull request #1200:
URL: https://github.com/apache/incubator-brpc/pull/1200#issuecomment-727818601
@zyearn 辛苦看下这个？理论分析上看是没有风险的
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[GitHub] [incubator-brpc] jamesge commented on a change in pull request #1200: reduce sampler's mutex scope
Posted by GitBox <gi...@apache.org>.
jamesge commented on a change in pull request #1200:
URL: https://github.com/apache/incubator-brpc/pull/1200#discussion_r525761185
##########
File path: src/bvar/detail/sampler.cpp
##########
@@ -147,31 +147,28 @@ void SamplerCollector::run() {
butil::LinkNode<Sampler> root;
int consecutive_nosleep = 0;
- while (!_stop) {
+ while (!_stop.load(butil::memory_order_relaxed)) {
int64_t abstime = butil::gettimeofday_us();
Sampler* s = this->reset();
if (s) {
s->InsertBeforeAsList(&root);
}
- int nremoved = 0;
- int nsampled = 0;
+
for (butil::LinkNode<Sampler>* p = root.next(); p != &root;) {
// We may remove p from the list, save next first.
butil::LinkNode<Sampler>* saved_next = p->next();
Sampler* s = p->value();
- s->_mutex.lock();
- if (!s->_used) {
- s->_mutex.unlock();
+ if (s->_used.load(butil::memory_order_acquire)) {
+ BAIDU_SCOPED_LOCK(s->_mutex);
Review comment:
这个_mutex也不太必要了，可以删掉
##########
File path: src/bvar/detail/sampler.cpp
##########
@@ -202,9 +199,7 @@ void Sampler::schedule() {
}
void Sampler::destroy() {
- _mutex.lock();
- _used = false;
- _mutex.unlock();
+ _used.store(false, butil::memory_order_release);
Review comment:
需要在注释里举一个场景说明一下为什么要release语意
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