commit 3f4349dc8b9494315f8331b2ea4e8d1f83fb801d
author Kevin Wolf <kwolf@redhat.com> Fri Jun 29 13:40:27 2012 +0200
committer Kevin Wolf <kwolf@redhat.com> Tue Jul 17 16:48:32 2012 +0200
tree 1e0267b1c907a90c3dddef494be13b9076fa2d9f
parent 9e559533bd825a3e371497875576137a8586c831

coroutine-ucontext: Help valgrind understand coroutines

valgrind tends to get confused and report false positives when you
switch stacks and don't tell it about it.

Signed-off-by: Kevin Wolf <kwolf@redhat.com>
Reviewed-by: Paolo Bonzini <pbonzini@redhat.com>

coroutine-ucontext.c

diff --git a/coroutine-ucontext.c b/coroutine-ucontext.c
index 5f43083..e3c450b 100644
--- a/coroutine-ucontext.c
+++ b/coroutine-ucontext.c
@@ -30,6 +30,10 @@
 #include "qemu-common.h"
 #include "qemu-coroutine-int.h"
 
+#ifdef CONFIG_VALGRIND_H
+#include <valgrind/valgrind.h>
+#endif
+
 enum {
     /* Maximum free pool size prevents holding too many freed coroutines */
     POOL_MAX_SIZE = 64,
@@ -43,6 +47,11 @@
     Coroutine base;
     void *stack;
     jmp_buf env;
+
+#ifdef CONFIG_VALGRIND_H
+    unsigned int valgrind_stack_id;
+#endif
+
 } CoroutineUContext;
 
 /**
@@ -159,6 +168,11 @@
     uc.uc_stack.ss_size = stack_size;
     uc.uc_stack.ss_flags = 0;
 
+#ifdef CONFIG_VALGRIND_H
+    co->valgrind_stack_id =
+        VALGRIND_STACK_REGISTER(co->stack, co->stack + stack_size);
+#endif
+
     arg.p = co;
 
     makecontext(&uc, (void (*)(void))coroutine_trampoline,
@@ -185,6 +199,16 @@
     return co;
 }
 
+#ifdef CONFIG_VALGRIND_H
+/* Work around an unused variable in the valgrind.h macro... */
+#pragma GCC diagnostic ignored "-Wunused-but-set-variable"
+static inline void valgrind_stack_deregister(CoroutineUContext *co)
+{
+    VALGRIND_STACK_DEREGISTER(co->valgrind_stack_id);
+}
+#pragma GCC diagnostic error "-Wunused-but-set-variable"
+#endif
+
 void qemu_coroutine_delete(Coroutine *co_)
 {
     CoroutineUContext *co = DO_UPCAST(CoroutineUContext, base, co_);
@@ -196,6 +220,10 @@
         return;
     }
 
+#ifdef CONFIG_VALGRIND_H
+    valgrind_stack_deregister(co);
+#endif
+
     g_free(co->stack);
     g_free(co);
 }