coroutine: move pooling to common code

The coroutine pool code is duplicated between the ucontext and
sigaltstack backends, and absent from the win32 backend.  But the
code can be shared easily by moving it to qemu-coroutine.c.

Signed-off-by: Paolo Bonzini <pbonzini@redhat.com>
Reviewed-by: Stefan Hajnoczi <stefanha@redhat.com>
Signed-off-by: Kevin Wolf <kwolf@redhat.com>
diff --git a/coroutine-sigaltstack.c b/coroutine-sigaltstack.c
index e37ebac..b4d1762 100644
--- a/coroutine-sigaltstack.c
+++ b/coroutine-sigaltstack.c
@@ -33,15 +33,6 @@
 #include "qemu-common.h"
 #include "block/coroutine_int.h"
 
-enum {
-    /* Maximum free pool size prevents holding too many freed coroutines */
-    POOL_MAX_SIZE = 64,
-};
-
-/** Free list to speed up creation */
-static QSLIST_HEAD(, Coroutine) pool = QSLIST_HEAD_INITIALIZER(pool);
-static unsigned int pool_size;
-
 typedef struct {
     Coroutine base;
     void *stack;
@@ -85,17 +76,6 @@
     g_free(s);
 }
 
-static void __attribute__((destructor)) coroutine_cleanup(void)
-{
-    Coroutine *co;
-    Coroutine *tmp;
-
-    QSLIST_FOREACH_SAFE(co, &pool, pool_next, tmp) {
-        g_free(DO_UPCAST(CoroutineUContext, base, co)->stack);
-        g_free(co);
-    }
-}
-
 static void __attribute__((constructor)) coroutine_init(void)
 {
     int ret;
@@ -164,7 +144,7 @@
     coroutine_bootstrap(self, co);
 }
 
-static Coroutine *coroutine_new(void)
+Coroutine *qemu_coroutine_new(void)
 {
     const size_t stack_size = 1 << 20;
     CoroutineUContext *co;
@@ -272,31 +252,10 @@
     return &co->base;
 }
 
-Coroutine *qemu_coroutine_new(void)
-{
-    Coroutine *co;
-
-    co = QSLIST_FIRST(&pool);
-    if (co) {
-        QSLIST_REMOVE_HEAD(&pool, pool_next);
-        pool_size--;
-    } else {
-        co = coroutine_new();
-    }
-    return co;
-}
-
 void qemu_coroutine_delete(Coroutine *co_)
 {
     CoroutineUContext *co = DO_UPCAST(CoroutineUContext, base, co_);
 
-    if (pool_size < POOL_MAX_SIZE) {
-        QSLIST_INSERT_HEAD(&pool, &co->base, pool_next);
-        co->base.caller = NULL;
-        pool_size++;
-        return;
-    }
-
     g_free(co->stack);
     g_free(co);
 }