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Why fiber::mutex yields in try_lock even after acquiring the lock successfully? #331

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Why fiber::mutex yields in try_lock even after acquiring the lock successfully?#331

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@rodman10
rodman10
opened on May 6, 2025

Recently I'm reading the source code of fiber::mutex, I noticed thatfiber::mutex will yield in try_lock no matter whether holding the lock or not? What's the considerations behind it, and can we just return immediately after lock? Thanks in advance.

fiber/src/mutex.cpp

Lines 43 to 60 in 238487b

bool
mutex::try_lock() {
context * active_ctx = context::active();
detail::spinlock_lock lk{ wait_queue_splk_ };
if ( BOOST_UNLIKELY( active_ctx == owner_) ) {
throw lock_error{
std::make_error_code( std::errc::resource_deadlock_would_occur),
"boost fiber: a deadlock is detected" };
}
if ( nullptr == owner_) {
owner_ = active_ctx;
}
lk.unlock();
// let other fiber release the lock
active_ctx->yield();
return active_ctx == owner_;
}

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Why `fiber::mutex` yields in `try_lock` even after acquiring the lock successfully? · Issue #331 · boostorg/fiber · GitHub
      Skip to content
      Why fiber::mutex yields in try_lock even after acquiring the lock successfully? #331
      Open
      Open
      Why fiber::mutex yields in try_lock even after acquiring the lock successfully?#331
      Description
      @rodman10
      rodman10
      opened on May 6, 2025
      Recently I'm reading the source code of fiber::mutex, I noticed thatfiber::mutex will yield in try_lock no matter whether holding the lock or not? What's the considerations behind it, and can we just return immediately after lock? Thanks in advance.
      fiber/src/mutex.cpp
      
Lines 43 to 60
in
238487b
      bool
      mutex::try_lock() { 
       context * active_ctx = context::active(); 
       detail::spinlock_lock lk{ wait_queue_splk_ }; 
      if ( BOOST_UNLIKELY( active_ctx == owner_) ) { 
      throw lock_error{ 
      std::make_error_code( std::errc::resource_deadlock_would_occur), 
      "boost fiber: a deadlock is detected" }; 
       } 
      if ( nullptr == owner_) { 
       owner_ = active_ctx; 
       } 
       lk.unlock(); 
      // let other fiber release the lock
       active_ctx->yield(); 
      return active_ctx == owner_; 
       } 
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var __m = "*";
var __re = new RegExp('^' + ".*" + '
Why `fiber::mutex` yields in `try_lock` even after acquiring the lock successfully? · Issue #331 · boostorg/fiber · GitHub
          Skip to content
          Why fiber::mutex yields in try_lock even after acquiring the lock successfully? #331
          Open
          Open
          Why fiber::mutex yields in try_lock even after acquiring the lock successfully?#331
          Description
          @rodman10
          rodman10
          opened on May 6, 2025
          Recently I'm reading the source code of fiber::mutex, I noticed thatfiber::mutex will yield in try_lock no matter whether holding the lock or not? What's the considerations behind it, and can we just return immediately after lock? Thanks in advance.
          fiber/src/mutex.cpp
          
Lines 43 to 60
in
238487b
          bool
          mutex::try_lock() { 
           context * active_ctx = context::active(); 
           detail::spinlock_lock lk{ wait_queue_splk_ }; 
          if ( BOOST_UNLIKELY( active_ctx == owner_) ) { 
          throw lock_error{ 
          std::make_error_code( std::errc::resource_deadlock_would_occur), 
          "boost fiber: a deadlock is detected" }; 
           } 
          if ( nullptr == owner_) { 
           owner_ = active_ctx; 
           } 
           lk.unlock(); 
          // let other fiber release the lock
           active_ctx->yield(); 
          return active_ctx == owner_; 
           } 
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var __m = "*";
var __re = new RegExp('^' + ".*" + '
Why `fiber::mutex` yields in `try_lock` even after acquiring the lock successfully? · Issue #331 · boostorg/fiber · GitHub
              Skip to content
              Why fiber::mutex yields in try_lock even after acquiring the lock successfully? #331
              Open
              Open
              Why fiber::mutex yields in try_lock even after acquiring the lock successfully?#331
              Description
              @rodman10
              rodman10
              opened on May 6, 2025
              Recently I'm reading the source code of fiber::mutex, I noticed thatfiber::mutex will yield in try_lock no matter whether holding the lock or not? What's the considerations behind it, and can we just return immediately after lock? Thanks in advance.
              fiber/src/mutex.cpp
              
Lines 43 to 60
in
238487b
              bool
              mutex::try_lock() { 
               context * active_ctx = context::active(); 
               detail::spinlock_lock lk{ wait_queue_splk_ }; 
              if ( BOOST_UNLIKELY( active_ctx == owner_) ) { 
              throw lock_error{ 
              std::make_error_code( std::errc::resource_deadlock_would_occur), 
              "boost fiber: a deadlock is detected" }; 
               } 
              if ( nullptr == owner_) { 
               owner_ = active_ctx; 
               } 
               lk.unlock(); 
              // let other fiber release the lock
               active_ctx->yield(); 
              return active_ctx == owner_; 
               } 
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var __re = new RegExp('^' + "youtube\\.com" + '
Why `fiber::mutex` yields in `try_lock` even after acquiring the lock successfully? · Issue #331 · boostorg/fiber · GitHub
                  Skip to content
                  Why fiber::mutex yields in try_lock even after acquiring the lock successfully? #331
                  Open
                  Open
                  Why fiber::mutex yields in try_lock even after acquiring the lock successfully?#331
                  Description
                  @rodman10
                  rodman10
                  opened on May 6, 2025
                  Recently I'm reading the source code of fiber::mutex, I noticed thatfiber::mutex will yield in try_lock no matter whether holding the lock or not? What's the considerations behind it, and can we just return immediately after lock? Thanks in advance.
                  fiber/src/mutex.cpp
                  
Lines 43 to 60
in
238487b
                  bool
                  mutex::try_lock() { 
                   context * active_ctx = context::active(); 
                   detail::spinlock_lock lk{ wait_queue_splk_ }; 
                  if ( BOOST_UNLIKELY( active_ctx == owner_) ) { 
                  throw lock_error{ 
                  std::make_error_code( std::errc::resource_deadlock_would_occur), 
                  "boost fiber: a deadlock is detected" }; 
                   } 
                  if ( nullptr == owner_) { 
                   owner_ = active_ctx; 
                   } 
                   lk.unlock(); 
                  // let other fiber release the lock
                   active_ctx->yield(); 
                  return active_ctx == owner_; 
                   } 
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try {
var __m = "*";
var __re = new RegExp('^' + ".*" + '
Why `fiber::mutex` yields in `try_lock` even after acquiring the lock successfully? · Issue #331 · boostorg/fiber · GitHub
                      Skip to content
                      Why fiber::mutex yields in try_lock even after acquiring the lock successfully? #331
                      Open
                      Open
                      Why fiber::mutex yields in try_lock even after acquiring the lock successfully?#331
                      Description
                      @rodman10
                      rodman10
                      opened on May 6, 2025
                      Recently I'm reading the source code of fiber::mutex, I noticed thatfiber::mutex will yield in try_lock no matter whether holding the lock or not? What's the considerations behind it, and can we just return immediately after lock? Thanks in advance.
                      fiber/src/mutex.cpp
                      
Lines 43 to 60
in
238487b
                      bool
                      mutex::try_lock() { 
                       context * active_ctx = context::active(); 
                       detail::spinlock_lock lk{ wait_queue_splk_ }; 
                      if ( BOOST_UNLIKELY( active_ctx == owner_) ) { 
                      throw lock_error{ 
                      std::make_error_code( std::errc::resource_deadlock_would_occur), 
                      "boost fiber: a deadlock is detected" }; 
                       } 
                      if ( nullptr == owner_) { 
                       owner_ = active_ctx; 
                       } 
                       lk.unlock(); 
                      // let other fiber release the lock
                       active_ctx->yield(); 
                      return active_ctx == owner_; 
                       } 
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(function(){
try {
var __m = "*";
var __re = new RegExp('^' + ".*" + '
Why `fiber::mutex` yields in `try_lock` even after acquiring the lock successfully? · Issue #331 · boostorg/fiber · GitHub
                          Skip to content
                          Why fiber::mutex yields in try_lock even after acquiring the lock successfully? #331
                          Open
                          Open
                          Why fiber::mutex yields in try_lock even after acquiring the lock successfully?#331
                          Description
                          @rodman10
                          rodman10
                          opened on May 6, 2025
                          Recently I'm reading the source code of fiber::mutex, I noticed thatfiber::mutex will yield in try_lock no matter whether holding the lock or not? What's the considerations behind it, and can we just return immediately after lock? Thanks in advance.
                          fiber/src/mutex.cpp
                          
Lines 43 to 60
in
238487b
                          bool
                          mutex::try_lock() { 
                           context * active_ctx = context::active(); 
                           detail::spinlock_lock lk{ wait_queue_splk_ }; 
                          if ( BOOST_UNLIKELY( active_ctx == owner_) ) { 
                          throw lock_error{ 
                          std::make_error_code( std::errc::resource_deadlock_would_occur), 
                          "boost fiber: a deadlock is detected" }; 
                           } 
                          if ( nullptr == owner_) { 
                           owner_ = active_ctx; 
                           } 
                           lk.unlock(); 
                          // let other fiber release the lock
                           active_ctx->yield(); 
                          return active_ctx == owner_; 
                           } 
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})();
Why `fiber::mutex` yields in `try_lock` even after acquiring the lock successfully? · Issue #331 · boostorg/fiber · GitHub
                              Skip to content
                              Why fiber::mutex yields in try_lock even after acquiring the lock successfully? #331
                              Open
                              Open
                              Why fiber::mutex yields in try_lock even after acquiring the lock successfully?#331
                              Description
                              @rodman10
                              rodman10
                              opened on May 6, 2025
                              Recently I'm reading the source code of fiber::mutex, I noticed thatfiber::mutex will yield in try_lock no matter whether holding the lock or not? What's the considerations behind it, and can we just return immediately after lock? Thanks in advance.
                              fiber/src/mutex.cpp
                              
Lines 43 to 60
in
238487b
                              bool
                              mutex::try_lock() { 
                               context * active_ctx = context::active(); 
                               detail::spinlock_lock lk{ wait_queue_splk_ }; 
                              if ( BOOST_UNLIKELY( active_ctx == owner_) ) { 
                              throw lock_error{ 
                              std::make_error_code( std::errc::resource_deadlock_would_occur), 
                              "boost fiber: a deadlock is detected" }; 
                               } 
                              if ( nullptr == owner_) { 
                               owner_ = active_ctx; 
                               } 
                               lk.unlock(); 
                              // let other fiber release the lock
                               active_ctx->yield(); 
                              return active_ctx == owner_; 
                               } 
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