From: Martin Quinson <martin.quinson@ens-rennes.fr>
Date: Mon, 7 Jan 2019 10:34:57 +0000 (+0100)
Subject: Fix a race condition
X-Git-Tag: v3_22~663
X-Git-Url: http://info.iut-bm.univ-fcomte.fr/pub/gitweb/simgrid.git/commitdiff_plain/aa9cfa5743045b941f3afca368462ea2be992a5f?hp=836d550dd0e6a85294e877cf7129b865bc0cb561

Fix a race condition

When saving the context of maestro, we must ensure that we are
actually thread 0. Otherwise, we may end up saving the context of a
minion (a working thread).
---

diff --git a/src/kernel/context/ContextSwapped.cpp b/src/kernel/context/ContextSwapped.cpp
index cb2f31487d..87da1fcf61 100644
--- a/src/kernel/context/ContextSwapped.cpp
+++ b/src/kernel/context/ContextSwapped.cpp
@@ -134,9 +134,16 @@ SwappedContext::~SwappedContext()
   xbt_free(stack_);
 }
 
+void SwappedContext::set_maestro(SwappedContext* ctx)
+{
+  if (factory_->threads_working_ == 0) // Don't save the soul of minions, only the one of maestro
+    factory_->workers_context_[0] = ctx;
+}
+
 void SwappedContext::stop()
 {
   Context::stop();
+  /* We must cut the actor execution using an exception to properly free the C++ RAII variables */
   throw StopRequest();
 }
 
diff --git a/src/kernel/context/ContextSwapped.hpp b/src/kernel/context/ContextSwapped.hpp
index 41a174720c..606dd447ce 100644
--- a/src/kernel/context/ContextSwapped.hpp
+++ b/src/kernel/context/ContextSwapped.hpp
@@ -45,7 +45,7 @@ public:
 
   virtual void swap_into(SwappedContext* to) = 0; // Defined in Raw, Boost and UContext subclasses
 
-  void set_maestro(SwappedContext* ctx) { factory_->workers_context_[0] = ctx; }
+  void set_maestro(SwappedContext* ctx);
 
   // FIXME: Killme
   static thread_local uintptr_t worker_id_;