From 1ff4a81bd3efb207992f1da267886fe0c4df764f Mon Sep 17 00:00:00 2001
From: Emilio Cota <cota@braap.org>
Date: Sun, 5 Feb 2023 11:37:58 -0500
Subject: tcg: use QTree instead of GTree
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qemu-user can hang in a multi-threaded fork. One common
reason is that when creating a TB, between fork and exec
we manipulate a GTree whose memory allocator (GSlice) is
not fork-safe.

Although POSIX does not mandate it, the system's allocator
(e.g. tcmalloc, libc malloc) is probably fork-safe.

Fix some of these hangs by using QTree, which uses the system's
allocator regardless of the Glib version that we used at
configuration time.

Tested with the test program in the original bug report, i.e.:
```

void garble() {
  int pid = fork();
  if (pid == 0) {
    exit(0);
  } else {
    int wstatus;
    waitpid(pid, &wstatus, 0);
  }
}

void supragarble(unsigned depth) {
  if (depth == 0)
    return ;

  std::thread a(supragarble, depth-1);
  std::thread b(supragarble, depth-1);
  garble();
  a.join();
  b.join();
}

int main() {
  supragarble(10);
}
```

Resolves: https://gitlab.com/qemu-project/qemu/-/issues/285
Reported-by: Valentin David <me@valentindavid.com>
Reviewed-by: Philippe Mathieu-Daudé <philmd@linaro.org>
Signed-off-by: Emilio Cota <cota@braap.org>
Message-Id: <20230205163758.416992-3-cota@braap.org>
[rth: Add QEMU_DISABLE_CFI for all callback using functions.]
Signed-off-by: Richard Henderson <richard.henderson@linaro.org>
---
 util/qtree.c | 8 ++++----
 1 file changed, 4 insertions(+), 4 deletions(-)

(limited to 'util')

diff --git a/util/qtree.c b/util/qtree.c
index deb46c1..31f0b46 100644
--- a/util/qtree.c
+++ b/util/qtree.c
@@ -310,7 +310,7 @@ q_tree_node_next(QTreeNode *node)
  *
  * Since: 2.70 in GLib. Internal in Qtree, i.e. not in the public API.
  */
-static void
+static void QEMU_DISABLE_CFI
 q_tree_remove_all(QTree *tree)
 {
     QTreeNode *node;
@@ -532,7 +532,7 @@ q_tree_replace(QTree    *tree,
 }
 
 /* internal insert routine */
-static QTreeNode *
+static QTreeNode * QEMU_DISABLE_CFI
 q_tree_insert_internal(QTree    *tree,
                        gpointer  key,
                        gpointer  value,
@@ -721,7 +721,7 @@ q_tree_steal(QTree         *tree,
 }
 
 /* internal remove routine */
-static gboolean
+static gboolean QEMU_DISABLE_CFI
 q_tree_remove_internal(QTree         *tree,
                        gconstpointer  key,
                        gboolean       steal)
@@ -1182,7 +1182,7 @@ q_tree_node_balance(QTreeNode *node)
     return node;
 }
 
-static QTreeNode *
+static QTreeNode * QEMU_DISABLE_CFI
 q_tree_find_node(QTree        *tree,
                  gconstpointer key)
 {
-- 
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