[yocto] [PATCH pseudo 2/2] Reset the pseudo mutex on fork

[Rabin Vincent]

From: Rabin Vincent <rabinv at axis.com>

When tclsh forks it can create new threads in the child process, in a
pthread_atfork() handler.  Running this under pseudo results in a
deadlock since the pseudo_lock() call in the new thread in the child
process premanently believes that the mutex is already locked by another
thread (which actually only existed in the parent process).

The provided test cases reproduces this.  Similar hangs can also been
seen in other cases, such as when attempting to use vim's cscope support
under pseudo.

Fix it by reseting the mutex in a pthread_atfork() child function.

Signed-off-by: Rabin Vincent <rabinv at axis.com>
---
 pseudo_wrappers.c       | 10 ++++++++++
 test/test-tclsh-fork.sh |  6 ++++++
 2 files changed, 16 insertions(+)
 create mode 100755 test/test-tclsh-fork.sh

diff --git a/pseudo_wrappers.c b/pseudo_wrappers.c
index 615ac9a..12bc541 100644
--- a/pseudo_wrappers.c
+++ b/pseudo_wrappers.c
@@ -98,8 +98,18 @@ extern int (*pseudo_real_lsetxattr)(const char *, const char *, const void *, si
 extern int (*pseudo_real_fsetxattr)(int, const char *, const void *, size_t, int);
 #endif
 
+static void libpseudo_atfork_child(void)
+{
+	pthread_mutex_init(&pseudo_mutex, NULL);
+	pseudo_mutex_recursion = 0;
+	pseudo_mutex_holder = 0;
+}
+
 static void
 _libpseudo_init(void) {
+	if (!_libpseudo_initted)
+		pthread_atfork(NULL, NULL, libpseudo_atfork_child);
+
 	pseudo_getlock();
 	pseudo_antimagic();
 	_libpseudo_initted = 1;
diff --git a/test/test-tclsh-fork.sh b/test/test-tclsh-fork.sh
new file mode 100755
index 0000000..e9dec66
--- /dev/null
+++ b/test/test-tclsh-fork.sh
@@ -0,0 +1,6 @@
+#!/bin/bash
+
+# Check that tclsh doesn't hang.  Note that the timeout is not needed to
+# reproduce the hang in tclsh, it's only there to ensure that this test script
+# doesn't hang in case of a failing test.
+timeout 2s bash -c "echo 'open {|true} r+' | tclsh"
-- 
2.1.4