apache · wwbmmm · Jan 6, 2025 · Dec 16, 2024 · Dec 19, 2024 · Dec 20, 2024
diff --git a/.github/actions/init-ut-make-config/action.yml b/.github/actions/init-ut-make-config/action.yml
@@ -0,0 +1,13 @@
+inputs:
+  options:
+    description: extra options for config_brpc.sh
+    required: false
+runs:
+  using: "composite"
+  steps:
+    - run: sudo git clone https://github.com/libunwind/libunwind.git && cd libunwind && sudo git checkout tags/v1.8.1 && sudo mkdir -p /libunwind && sudo autoreconf -i && sudo CC=clang CXX=clang++ ./configure --prefix=/libunwind && sudo make -j ${{env.proc_num}} && sudo make install
+      shell: bash
+    - run: sudo apt-get update && sudo apt-get install -y libgtest-dev cmake gdb libstdc++6-9-dbg && cd /usr/src/gtest && sudo cmake . && sudo make -j ${{env.proc_num}} && sudo mv lib/libgtest* /usr/lib/
+      shell: bash
+    - run: sh config_brpc.sh --headers="/libunwind/include /usr/include" --libs="/libunwind/lib /usr/lib /usr/lib64" --nodebugsymbols ${{inputs.options}}
+      shell: bash
diff --git a/.github/actions/install-all-dependences/action.yml b/.github/actions/install-all-dependences/action.yml
@@ -2,7 +2,7 @@ runs:
   using: "composite"
   steps:
     - uses: ./.github/actions/install-essential-dependences
-    - run: sudo apt-get install -y libgoogle-glog-dev automake bison flex libboost-all-dev libevent-dev libtool pkg-config  libibverbs1 libibverbs-dev
+    - run: sudo apt-get install -y libgoogle-glog-dev automake bison flex libboost-all-dev libevent-dev libtool pkg-config  libibverbs1 libibverbs-dev  libunwind8-dev
       shell: bash
     - run: wget https://archive.apache.org/dist/thrift/0.11.0/thrift-0.11.0.tar.gz && tar -xf thrift-0.11.0.tar.gz
       shell: bash

diff --git a/.github/workflows/ci-linux.yml b/.github/workflows/ci-linux.yml
@@ -31,7 +31,7 @@ jobs:
     steps:
     - uses: actions/checkout@v2
     - uses: ./.github/actions/install-essential-dependences
-    - name: cmake 
+    - name: cmake
       run: |
            export CC=gcc && export CXX=g++
            mkdir build
@@ -47,7 +47,7 @@ jobs:
     steps:
     - uses: actions/checkout@v2
     - run: bazel test --verbose_failures -- //... -//example/...
-  
+
   gcc-compile-with-boringssl:
     runs-on: ubuntu-20.04
     steps:
@@ -61,7 +61,7 @@ jobs:
     - uses: ./.github/actions/install-all-dependences
     - uses: ./.github/actions/init-make-config
       with:
-       options: --cc=gcc --cxx=g++ --with-thrift --with-glog --with-rdma  --with-debug-bthread-sche-safety --with-debug-lock
+       options: --cc=gcc --cxx=g++ --with-thrift --with-glog --with-rdma  --with-debug-bthread-sche-safety --with-debug-lock --with-bthread-tracer
     - name: compile
       run: |
         make -j ${{env.proc_num}}
@@ -76,7 +76,7 @@ jobs:
            export CC=gcc && export CXX=g++
            mkdir build
            cd build
-           cmake -DWITH_MESALINK=OFF -DWITH_GLOG=ON -DWITH_THRIFT=ON -DWITH_RDMA=ON -DWITH_DEBUG_BTHREAD_SCHE_SAFETY=ON -DWITH_DEBUG_LOCK=ON ..
+           cmake -DWITH_MESALINK=OFF -DWITH_GLOG=ON -DWITH_THRIFT=ON -DWITH_RDMA=ON -DWITH_DEBUG_BTHREAD_SCHE_SAFETY=ON -DWITH_DEBUG_LOCK=ON -WITH_BTHREAD_TRACER=ON ..
     - name: compile
       run: |
            cd build
@@ -105,7 +105,7 @@ jobs:
     steps:
     - uses: actions/checkout@v2
     - uses: ./.github/actions/install-essential-dependences
-    - name: cmake 
+    - name: cmake
       run: |
            export CC=clang && export CXX=clang++
            mkdir build
@@ -135,7 +135,7 @@ jobs:
     - uses: ./.github/actions/install-all-dependences
     - uses: ./.github/actions/init-make-config
       with:
-        options: --cc=clang --cxx=clang++ --with-thrift --with-glog --with-rdma  --with-debug-bthread-sche-safety --with-debug-lock
+        options: --cc=clang --cxx=clang++ --with-thrift --with-glog --with-rdma  --with-debug-bthread-sche-safety --with-debug-lock --with-bthread-tracer
     - name: compile
       run: |
            make -j ${{env.proc_num}}
@@ -150,7 +150,7 @@ jobs:
            export CC=clang && export CXX=clang++
            mkdir build
            cd build
-           cmake -DWITH_MESALINK=OFF -DWITH_GLOG=ON -DWITH_THRIFT=ON -DWITH_RDMA=ON -DWITH_DEBUG_BTHREAD_SCHE_SAFETY=ON -DWITH_DEBUG_LOCK=ON ..
+           cmake -DWITH_MESALINK=OFF -DWITH_GLOG=ON -DWITH_THRIFT=ON -DWITH_RDMA=ON -DWITH_DEBUG_BTHREAD_SCHE_SAFETY=ON -DWITH_DEBUG_LOCK=ON -WITH_BTHREAD_TRACER=ON ..
     - name: compile
       run: |
            cd build
@@ -165,21 +165,17 @@ jobs:
   clang-unittest:
     runs-on: ubuntu-20.04
     steps:
-    - uses: actions/checkout@v2
-    - uses: ./.github/actions/install-essential-dependences
-    - name: install gtest
-      run: |
-           sudo apt-get update
-           sudo apt-get install -y cmake libgtest-dev gdb
-           cd /usr/src/gtest && sudo cmake . && sudo make && sudo mv lib/libgtest* /usr/lib/
-    - uses: ./.github/actions/init-make-config
-      with:
-        options: --cc=clang --cxx=clang++
-    - name: compile tests
-      run: |
-           cd test
-           make -j ${{env.proc_num}}
-    - name: run tests
-      run: |
-           cd test
-           sh ./run_tests.sh
+      - uses: actions/checkout@v2
+      - uses: ./.github/actions/install-essential-dependences
+      - uses: ./.github/actions/init-ut-make-config
+        with:
+          options: --cc=clang --cxx=clang++ --with-bthread-tracer
+      - name: compile tests
+        run: |
+          cat config.mk
+          cd test
+          make -j ${{env.proc_num}}
+      - name: run tests
+        run: |
+          cd test
+          sh ./run_tests.sh
diff --git a/CMakeLists.txt b/CMakeLists.txt
@@ -24,6 +24,7 @@ option(WITH_BORINGSSL "With BoringSSL" OFF)
 option(DEBUG "Print debug logs" OFF)
 option(WITH_DEBUG_SYMBOLS "With debug symbols" ON)
 option(WITH_THRIFT "With thrift framed protocol supported" OFF)
+option(WITH_BTHREAD_TRACER "With bthread tracer supported" OFF)
 option(WITH_SNAPPY "With snappy" OFF)
 option(WITH_RDMA "With RDMA" OFF)
 option(WITH_DEBUG_BTHREAD_SCHE_SAFETY "With debugging bthread sche safety" OFF)
@@ -81,6 +82,20 @@ if(WITH_THRIFT)
     endif()
 endif()
 
+if (WITH_BTHREAD_TRACER)
+    if (NOT (CMAKE_SYSTEM_NAME STREQUAL "Linux")  OR NOT (CMAKE_SYSTEM_PROCESSOR MATCHES "x86_64"))
+        message(FATAL_ERROR "bthread tracer is only supported on Linux x86_64 platform")
+    endif()
+    find_path(LIBUNWIND_INCLUDE_PATH NAMES libunwind.h)
+    find_library(LIBUNWIND_LIB NAMES unwind)
+    find_library(LIBUNWIND_X86_64_LIB NAMES unwind-x86_64)
+    if (NOT LIBUNWIND_INCLUDE_PATH OR NOT LIBUNWIND_LIB)
+        message(FATAL_ERROR "Fail to find libunwind, which is needed by bthread tracer")
+    endif()
+    add_definitions(-DBRPC_BTHREAD_TRACER)
+    include_directories(${LIBUNWIND_INCLUDE_PATH})
+endif ()
+
 set(WITH_RDMA_VAL "0")
 if(WITH_RDMA)
     set(WITH_RDMA_VAL "1")
@@ -319,6 +334,11 @@ if(WITH_SNAPPY)
     set(BRPC_PRIVATE_LIBS "${BRPC_PRIVATE_LIBS} -lsnappy")
 endif()
 
+if (WITH_BTHREAD_TRACER)
+    set(DYNAMIC_LIB ${DYNAMIC_LIB} ${LIBUNWIND_LIB} ${LIBUNWIND_X86_64_LIB})
+    set(BRPC_PRIVATE_LIBS "${BRPC_PRIVATE_LIBS} -lunwind -lunwind-x86_64")
+endif()
+
 if(CMAKE_SYSTEM_NAME STREQUAL "Linux")
     set(DYNAMIC_LIB ${DYNAMIC_LIB} rt)
     set(BRPC_PRIVATE_LIBS "${BRPC_PRIVATE_LIBS} -lrt")

diff --git a/README_cn.md b/README_cn.md
@@ -38,6 +38,7 @@
     * [bthread or not](docs/cn/bthread_or_not.md)
     * [thread-local](docs/cn/thread_local.md)
     * [Execution Queue](docs/cn/execution_queue.md)
+    * [bthread tracer](docs/cn/bthread_tracer.md)
   * Client
     * [基础功能](docs/cn/client.md)
     * [错误码](docs/cn/error_code.md)

diff --git a/config_brpc.sh b/config_brpc.sh
@@ -38,11 +38,12 @@ else
     LDD=ldd
 fi
 
-TEMP=`getopt -o v: --long headers:,libs:,cc:,cxx:,with-glog,with-thrift,with-rdma,with-mesalink,with-debug-bthread-sche-safety,with-debug-lock,nodebugsymbols -n 'config_brpc' -- "$@"`
+TEMP=`getopt -o v: --long headers:,libs:,cc:,cxx:,with-glog,with-thrift,with-rdma,with-mesalink,with-bthread-tracer,with-debug-bthread-sche-safety,with-debug-lock,nodebugsymbols -n 'config_brpc' -- "$@"`
 WITH_GLOG=0
 WITH_THRIFT=0
 WITH_RDMA=0
 WITH_MESALINK=0
+WITH_BTHREAD_TRACER=0
 BRPC_DEBUG_BTHREAD_SCHE_SAFETY=0
 DEBUGSYMBOLS=-g
 BRPC_DEBUG_LOCK=0
@@ -69,6 +70,7 @@ while true; do
         --with-thrift) WITH_THRIFT=1; shift 1 ;;
         --with-rdma) WITH_RDMA=1; shift 1 ;;
         --with-mesalink) WITH_MESALINK=1; shift 1 ;;
+        --with-bthread-tracer) WITH_BTHREAD_TRACER=1; shift 1 ;;
         --with-debug-bthread-sche-safety ) BRPC_DEBUG_BTHREAD_SCHE_SAFETY=1; shift 1 ;;
         --with-debug-lock ) BRPC_DEBUG_LOCK=1; shift 1 ;;
         --nodebugsymbols ) DEBUGSYMBOLS=; shift 1 ;;
@@ -352,8 +354,27 @@ fi
 
 LEVELDB_HDR=$(find_dir_of_header_or_die leveldb/db.h)
 
-HDRS=$($ECHO "$GFLAGS_HDR\n$PROTOBUF_HDR\n$ABSL_HDR\n$LEVELDB_HDR\n$OPENSSL_HDR" | sort | uniq)
-LIBS=$($ECHO "$GFLAGS_LIB\n$PROTOBUF_LIB\n$ABSL_LIB\n$LEVELDB_LIB\n$OPENSSL_LIB\n$SNAPPY_LIB" | sort | uniq)
+CPPFLAGS=
+
+if [ $WITH_BTHREAD_TRACER != 0 ]; then
+    if [ "$SYSTEM" != "Linux" ] || [ "$(uname -m)" != "x86_64" ]; then
+        >&2 $ECHO "bthread tracer is only supported on Linux x86_64 platform"
+        exit 1
+    fi
+    LIBUNWIND_HDR=$(find_dir_of_header_or_die libunwind.h)
+    LIBUNWIND_LIB=$(find_dir_of_lib_or_die unwind)
+
+    CPPFLAGS="${CPPFLAGS} -DBRPC_BTHREAD_TRACER"
+
+    if [ -f "$LIBUNWIND_LIB/libunwind.$SO" ]; then
+        DYNAMIC_LINKINGS="$DYNAMIC_LINKINGS -lunwind -lunwind-x86_64"
+    else
+        STATIC_LINKINGS="$STATIC_LINKINGS -lunwind -lunwind-x86_64"
+    fi
+fi
+
+HDRS=$($ECHO "$LIBUNWIND_HDR\n$GFLAGS_HDR\n$PROTOBUF_HDR\n$ABSL_HDR\n$LEVELDB_HDR\n$OPENSSL_HDR" | sort | uniq)
+LIBS=$($ECHO "$LIBUNWIND_LIB\n$GFLAGS_LIB\n$PROTOBUF_LIB\n$ABSL_LIB\n$LEVELDB_LIB\n$OPENSSL_LIB\n$SNAPPY_LIB" | sort | uniq)
 
 absent_in_the_list() {
     TMP=`$ECHO "$1\n$2" | sort | uniq`
@@ -411,7 +432,7 @@ append_to_output "STATIC_LINKINGS=$STATIC_LINKINGS"
 append_to_output "DYNAMIC_LINKINGS=$DYNAMIC_LINKINGS"
 
 # CPP means C PreProcessing, not C PlusPlus
-CPPFLAGS="-DBRPC_WITH_GLOG=$WITH_GLOG -DGFLAGS_NS=$GFLAGS_NS -DBRPC_DEBUG_BTHREAD_SCHE_SAFETY=$BRPC_DEBUG_BTHREAD_SCHE_SAFETY -DBRPC_DEBUG_LOCK=$BRPC_DEBUG_LOCK"
+CPPFLAGS="${CPPFLAGS}  -DBRPC_WITH_GLOG=$WITH_GLOG -DGFLAGS_NS=$GFLAGS_NS -DBRPC_DEBUG_BTHREAD_SCHE_SAFETY=$BRPC_DEBUG_BTHREAD_SCHE_SAFETY -DBRPC_DEBUG_LOCK=$BRPC_DEBUG_LOCK"
 
 # Avoid over-optimizations of TLS variables by GCC>=4.8
 # See: https://github.com/apache/brpc/issues/1693

diff --git a/docs/cn/bthread_tracer.md b/docs/cn/bthread_tracer.md
@@ -0,0 +1,79 @@
+gdb（ptrace）+ gdb_bthread_stack.py主要的缺点是要慢和阻塞进程，需要一种高效的追踪bthread调用栈的方法。
+
+bRPC框架的协作式用户态协程无法像Golang内建的抢占式协程一样实现高效的STW（Stop the World），框架也无法干预用户逻辑的执行，所以要追踪bthread调用栈是比较困难的。
+
+在线追踪bthread调用栈需要解决以下问题：
+1. 追踪挂起bthread的调用栈。 
+2. 追踪运行中bthread的调用栈。
+
+# bthread状态模型
+
+以下是目前的bthread状态模型。
+
+![bthread状态模型](../images/bthread_status_model.svg)
+
+# 设计方案
+
+## 核心思路
+
+为了解决上述两个问题，该方案实现了STB（Stop The Bthread），核心思路可以简单总结为，在追踪bthread调用栈的过程中，状态不能流转到当前追踪方法不支持的状态。STB包含了两种追踪模式：上下文（context）追踪模式和信号追踪模式。
+
+### 上下文（context）追踪模式
+上下文追踪模式可以追踪挂起bthread的调用栈。挂起的bthread栈是稳定的，利用TaskMeta.stack中保存的上下文信息（x86_64下关键的寄存器主要是RIP、RSP、RBP），通过一些可以回溯指定上下文调用栈的库来追踪bthread调用栈。但是挂起的bthread随时可能会被唤醒，执行逻辑（包括jump_stack），则bthread栈会一直变化。不稳定的上下文是不能用来追踪调用栈的，需要在jump_stack前拦截bthread的调度，等到调用栈追踪完成后才继续运行bthread。所以，上下文追踪模式支持就绪、挂起这两个状态。
+
+### 信号追踪模式
+
+信号追踪模式可以追踪运行中bthread的调用栈。运行中bthread是不稳定的，不能使用TaskMeta.stack来追踪bthread调用栈。只能另辟蹊径，使用信号中断bthread运行逻辑，在信号处理函数中回溯bthread调用栈。使用信号有两个问题：
+
+1. 异步信号安全问题。
+2. 信号追踪模式不支持jump_stack。调用栈回溯需要寄存器信息，但jump_stack会操作寄存器，这个过程是不安全的，所以jump_stack不能被信号中断，需要在jump_stack前拦截bthread的调度，等到bthread调用栈追踪完成后才继续挂起bthread。
+
+所以，追踪模式只支持运行状态。
+
+### 小结
+
+jump_stack是bthread挂起或者运行的必经之路，也是STB的拦截点。STB将状态分成三类：
+1. 上下文追踪模式的状态：就绪、挂起。
+2. 支持信号追踪模式的状态：运行。
+3. 不支持追踪的状态。jump_stack的过程是不允许使用以上两种调用栈追踪方法，需要在jump_stack前拦截bthread的调度，等到调用栈追踪完成后才继续调度bthread。
+
+### 详细流程
+
+以下是引入STB后的bthread状态模型，在原来bthread状态模型的基础上，加入两个状态（拦截点）：将运行、挂起中。
+
+![bthread STB状态模型](../images/bthread_stb_model.svg)
+
+经过上述分析，总结出STB的流程：
+
+1. TaskTracer（实现STB的一个模块）收到追踪bthread调用栈的请求时，标识正在追踪。追踪完成后，标识追踪完成，并TaskTracer发信号通知可能处于将运行或者挂起中状态的bthread。根据bthread状态，TaskTracer执行不同的逻辑：
+- 创建、就绪但还没分配栈、销毁：直接结束追踪。
+- 挂起、就绪：使用上下文追踪模式追踪bthread的调用栈。
+- 运行：使用信号追踪模式追踪bthread的调用栈。
+- 将运行、挂起中：TaskTracer自旋等到bthread状态流转到下一个状态（挂起或者运行）后继续追踪。
+
+2. TaskTracer追踪时，bthread根据状态也会执行不同的逻辑：
+- 创建、就绪但还没分配栈、就绪：不需要额外处理。
+- 挂起、运行：通知TaskTracer继续追踪。
+- 将运行、挂起中、销毁：bthread通过条件变量等到TaskTracer追踪完成。TaskTracer追踪完成后会通过条件变量通知bthread继续执行jump_stack。
+
+# 使用方法
+
+1. 下载安装libunwind。
+2. 给config_brpc.sh增加`--with-bthread-tracer`选项或者给cmake增加`-DWITH_BTHREAD_TRACER=ON`选项。
+3. 访问服务的内置服务：`http://ip:port/bthreads/<bthread_id>?st=1`或者代码里调用`bthread::stack_trace()`函数。
+4. 如果希望追踪pthread的调用栈，在对应pthread上调用`bthread::init_for_pthread_stack_trace()`函数获取一个伪bthread_t，然后使用步骤3即可获取pthread调用栈。
+
+下面是追踪bthread调用栈的输出示例：
+```shell
+#0 0x00007fdbbed500b5 __clock_gettime_2
+#1 0x000000000041f2b6 butil::cpuwide_time_ns()
+#2 0x000000000041f289 butil::cpuwide_time_us()
+#3 0x000000000041f1b9 butil::EveryManyUS::operator bool()
+#4 0x0000000000413289 (anonymous namespace)::spin_and_log()
+#5 0x00007fdbbfa58dc0 bthread::TaskGroup::task_runner()
+```
+
+# 相关flag
+
+- `enable_fast_unwind`：是否启用快速回溯功能，默认为true。大多数情况下，不需要关闭快速回溯功能。除非你关注的调用栈函数名转换失败，显示为`<unknown>`，则可以尝试关闭快速回溯功能，但这会导致性能下降。以包含30帧的调用栈举例，快速回溯基本上在200us以内就可以完成，而关闭快速回溯则需要4ms左右，性能下降了近20倍。
+- `signal_trace_timeout_ms`：信号追踪模式的超时时间，默认为50ms。虽然libunwind文档显示回溯功能是异步信号安全的，但是[gpertools社区发现libunwind在某些情况下会死锁](https://github.com/gperftools/gperftools/issues/775)，所以TaskTracer会设置了超时时间，超时后会放弃回溯，打破死锁。
diff --git a/docs/cn/getting_started.md b/docs/cn/getting_started.md
@@ -382,7 +382,7 @@ brpc默认**不**链接 [tcmalloc](http://goog-perftools.sourceforge.net/doc/tcm
 
 ## glog: 3.3+
 
-brpc实现了一个默认的[日志功能](../../src/butil/logging.h)它和glog冲突。要替换成glog，可以给config_brpc.sh增加*--with-glog*选项或者给cmake增加`-DWITH_GLOG=ON`选项。
+brpc实现了一个默认的[日志功能](../../src/butil/logging.h)它和glog冲突。要替换成glog，可以给config_brpc.sh增加`--with-glog`选项或者给cmake增加`-DWITH_GLOG=ON`选项。
 
 ## valgrind: 3.8+
 
@@ -392,6 +392,12 @@ brpc会自动检测valgrind（然后注册bthread的栈）。不支持老版本
 
 无已知问题。
 
+## libunwind: 1.3-1.8.1
+
+bRPC默认**不**链接 [libunwind](https://github.com/libunwind/libunwind)。用户需要追踪bthread功能则链接libunwind，可以给config_brpc.sh增加`--with-bthread-tracer`选项或者给cmake增加`-DWITH_BTHREAD_TRACER=ON`选项。
+
+建议使用最新版本的libunwind。
+
 # 实例追踪
 
 我们提供了一个程序去帮助你追踪和监控所有brpc实例。 只需要在某处运行 [trackme_server](https://github.com/apache/brpc/tree/master/tools/trackme_server/) 然后再带着 -trackme_server=SERVER参数启动需要被追踪的实例。trackme_server将从实例周期性地收到ping消息然后打印日志。您可以从日志中聚合实例地址，并调用实例的内置服务以获取更多信息。
diff --git a/docs/en/getting_started.md b/docs/en/getting_started.md
@@ -377,14 +377,20 @@ When you remove tcmalloc, not only remove the linkage with tcmalloc but also the
 
 ## glog: 3.3+
 
-brpc implements a default [logging utility](../../src/butil/logging.h) which conflicts with glog. To replace this with glog, add *--with-glog* to config_brpc.sh or add `-DWITH_GLOG=ON` to cmake.
+brpc implements a default [logging utility](../../src/butil/logging.h) which conflicts with glog. To replace this with glog, add `--with-glog` to config_brpc.sh or add `-DWITH_GLOG=ON` to cmake.
 
 ## valgrind: 3.8+
 
 brpc detects valgrind automatically (and registers stacks of bthread). Older valgrind(say 3.2) is not supported.
 
 ## thrift: 0.9.3-0.11.0
 
+## libunwind: 1.3-1.8.1
+
+brpc does **not** link [libunwind](https://github.com/libunwind/libunwind) by default. Users link libunwind on-demand by adding `--with-glog` to config_brpc.sh or adding `-DWITH_GLOG=ON` to cmake.
+
+It is recommended to use the latest possible version of libunwind.
+
 no known issues.
 
 # Track instances

diff --git a/docs/images/bthread_status_model.svg b/docs/images/bthread_status_model.svg
diff --git a/docs/images/bthread_stb_model.svg b/docs/images/bthread_stb_model.svg
diff --git a/src/brpc/builtin/bthreads_service.cpp b/src/brpc/builtin/bthreads_service.cpp
@@ -16,14 +16,14 @@
 // under the License.
 
 
-#include <ostream>
+#include "bthread/bthread.h"
 #include "brpc/closure_guard.h"        // ClosureGuard
 #include "brpc/controller.h"           // Controller
 #include "brpc/builtin/common.h"
 #include "brpc/builtin/bthreads_service.h"
 
 namespace bthread {
-void print_task(std::ostream& os, bthread_t tid);
+extern void print_task(std::ostream& os, bthread_t tid);
 }
 
 
@@ -40,12 +40,24 @@ void BthreadsService::default_method(::google::protobuf::RpcController* cntl_bas
     const std::string& constraint = cntl->http_request().unresolved_path();
 
     if (constraint.empty()) {
+#ifdef BRPC_BTHREAD_TRACER
+        os << "Use /bthreads/<bthread_id> or /bthreads/<bthread_id>?st=1 for stack trace";
+#else
         os << "Use /bthreads/<bthread_id>";
+#endif // BRPC_BTHREAD_TRACER
     } else {
         char* endptr = NULL;
         bthread_t tid = strtoull(constraint.c_str(), &endptr, 10);
-        if (*endptr == '\0' || *endptr == '/') {
+        if (*endptr == '\0' || *endptr == '/' || *endptr == '?') {
             ::bthread::print_task(os, tid);
+
+#ifdef BRPC_BTHREAD_TRACER
+            const std::string* st = cntl->http_request().uri().GetQuery("st");
+            if (NULL != st && *st == "1") {
+                os << "\nbthread call stack:\n";
+                ::bthread::stack_trace(os, tid);
+            }
+#endif // BRPC_BTHREAD_TRACER
         } else {
             cntl->SetFailed(ENOMETHOD, "path=%s is not a bthread id",
                             constraint.c_str());