[Boost-commit] svn:boost r39752 - trunk/boost/asio/detail

From: chris_at_[hidden]
Date: 2007-10-06 20:11:26

Author: chris_kohlhoff
Date: 2007-10-06 20:11:25 EDT (Sat, 06 Oct 2007)
New Revision: 39752
URL: http://svn.boost.org/trac/boost/changeset/39752

Log:
The epoll_wait function can produce EPOLLHUP events for a descriptor even
if not specifically requested, resulting in a tight loop of calls to
epoll_wait. Delete a descriptor from epoll if an EPOLLHUP event is
received and there are no registered operations for the descriptor.

Text files modified: 
   trunk/boost/asio/detail/epoll_reactor.hpp |    60 ++++++++++++++++++++++++++++----------- 
   1 files changed, 43 insertions(+), 17 deletions(-)

Modified: trunk/boost/asio/detail/epoll_reactor.hpp
==============================================================================
--- trunk/boost/asio/detail/epoll_reactor.hpp	(original)
+++ trunk/boost/asio/detail/epoll_reactor.hpp	2007-10-06 20:11:25 EDT (Sat, 06 Oct 2007)
@@ -156,6 +156,8 @@
       ev.data.fd = descriptor;
 
       int result = epoll_ctl(epoll_fd_, EPOLL_CTL_MOD, descriptor, &ev);
+      if (result != 0 && errno == ENOENT)
+        result = epoll_ctl(epoll_fd_, EPOLL_CTL_ADD, descriptor, &ev);
       if (result != 0)
       {
         boost::system::error_code ec(errno,
@@ -190,6 +192,8 @@
       ev.data.fd = descriptor;
 
       int result = epoll_ctl(epoll_fd_, EPOLL_CTL_MOD, descriptor, &ev);
+      if (result != 0 && errno == ENOENT)
+        result = epoll_ctl(epoll_fd_, EPOLL_CTL_ADD, descriptor, &ev);
       if (result != 0)
       {
         boost::system::error_code ec(errno,
@@ -220,6 +224,8 @@
       ev.data.fd = descriptor;
 
       int result = epoll_ctl(epoll_fd_, EPOLL_CTL_MOD, descriptor, &ev);
+      if (result != 0 && errno == ENOENT)
+        result = epoll_ctl(epoll_fd_, EPOLL_CTL_ADD, descriptor, &ev);
       if (result != 0)
       {
         boost::system::error_code ec(errno,
@@ -252,6 +258,8 @@
       ev.data.fd = descriptor;
 
       int result = epoll_ctl(epoll_fd_, EPOLL_CTL_MOD, descriptor, &ev);
+      if (result != 0 && errno == ENOENT)
+        result = epoll_ctl(epoll_fd_, EPOLL_CTL_ADD, descriptor, &ev);
       if (result != 0)
       {
         boost::system::error_code ec(errno,
@@ -420,23 +428,40 @@
         else
           more_writes = write_op_queue_.has_operation(descriptor);
 
-        epoll_event ev = { 0, { 0 } };
-        ev.events = EPOLLERR | EPOLLHUP;
-        if (more_reads)
-          ev.events |= EPOLLIN;
-        if (more_writes)
-          ev.events |= EPOLLOUT;
-        if (more_except)
-          ev.events |= EPOLLPRI;
-        ev.data.fd = descriptor;
-        int result = epoll_ctl(epoll_fd_, EPOLL_CTL_MOD, descriptor, &ev);
-        if (result != 0)
+        if ((events[i].events == EPOLLHUP)
+            && !more_except && !more_reads && !more_writes)
         {
-          ec = boost::system::error_code(errno,
-              boost::asio::error::system_category);
-          read_op_queue_.dispatch_all_operations(descriptor, ec);
-          write_op_queue_.dispatch_all_operations(descriptor, ec);
-          except_op_queue_.dispatch_all_operations(descriptor, ec);
+          // If we have only an EPOLLHUP event and no operations associated
+          // with the descriptor then we need to delete the descriptor from
+          // epoll. The epoll_wait system call will produce EPOLLHUP events
+          // even if they are not specifically requested, so if we do not
+          // remove the descriptor we can end up in a tight loop of repeated
+          // calls to epoll_wait.
+          epoll_event ev = { 0, { 0 } };
+          epoll_ctl(epoll_fd_, EPOLL_CTL_DEL, descriptor, &ev);
+        }
+        else
+        {
+          epoll_event ev = { 0, { 0 } };
+          ev.events = EPOLLERR | EPOLLHUP;
+          if (more_reads)
+            ev.events |= EPOLLIN;
+          if (more_writes)
+            ev.events |= EPOLLOUT;
+          if (more_except)
+            ev.events |= EPOLLPRI;
+          ev.data.fd = descriptor;
+          int result = epoll_ctl(epoll_fd_, EPOLL_CTL_MOD, descriptor, &ev);
+          if (result != 0 && errno == ENOENT)
+            result = epoll_ctl(epoll_fd_, EPOLL_CTL_ADD, descriptor, &ev);
+          if (result != 0)
+          {
+            ec = boost::system::error_code(errno,
+                boost::asio::error::system_category);
+            read_op_queue_.dispatch_all_operations(descriptor, ec);
+            write_op_queue_.dispatch_all_operations(descriptor, ec);
+            except_op_queue_.dispatch_all_operations(descriptor, ec);
+          }
         }
       }
     }
@@ -532,7 +557,8 @@
 
     if (minimum_wait_duration > boost::posix_time::time_duration())
     {
-      return minimum_wait_duration.total_milliseconds();
+      int milliseconds = minimum_wait_duration.total_milliseconds();
+      return milliseconds > 0 ? milliseconds : 1;
     }
     else
     {