[Qemu-devel] [PATCH] tests: Fix signalling race condition in TPM tests

[Stefan Berger]

Hi Michael,

   please apply the below patch to the 2.12 stable tree. It is a backport
of commit 2271b75fa9019 from master.

   For a 3.0 stable branch 'git cherry-pick 2271b75fa9019' should work.

Regards,
    Stefan

This patch fixes a race condition and test failure where the main process
waits for the signal of a thread but the thread already sent that signal
via a condition. Since these signals are non-sticky, we need to introduce a
separate variable to make this signal sticky.

Signed-off-by: Stefan Berger <address@hidden>
Reviewed-by: Marc-André Lureau <address@hidden>
---
 tests/tpm-crb-test.c |  1 +
 tests/tpm-emu.c      | 11 ++++++++++-
 tests/tpm-emu.h      |  1 +
 tests/tpm-tis-test.c |  1 +
 4 files changed, 13 insertions(+), 1 deletion(-)

diff --git a/tests/tpm-crb-test.c b/tests/tpm-crb-test.c
index d8f9569203..6fde579bab 100644
--- a/tests/tpm-crb-test.c
+++ b/tests/tpm-crb-test.c
@@ -151,6 +151,7 @@ int main(int argc, char **argv)
     test.addr->u.q_unix.path = g_build_filename(tmp_path, "sock", NULL);
     g_mutex_init(&test.data_mutex);
     g_cond_init(&test.data_cond);
+    test.data_cond_signal = false;
 
     thread = g_thread_new(NULL, tpm_emu_ctrl_thread, &test);
     tpm_emu_test_wait_cond(&test);
diff --git a/tests/tpm-emu.c b/tests/tpm-emu.c
index 8c2bd53cad..125e697181 100644
--- a/tests/tpm-emu.c
+++ b/tests/tpm-emu.c
@@ -23,9 +23,14 @@ void tpm_emu_test_wait_cond(TestState *s)
     gint64 end_time = g_get_monotonic_time() + 5 * G_TIME_SPAN_SECOND;
 
     g_mutex_lock(&s->data_mutex);
-    if (!g_cond_wait_until(&s->data_cond, &s->data_mutex, end_time)) {
+
+    if (!s->data_cond_signal &&
+        !g_cond_wait_until(&s->data_cond, &s->data_mutex, end_time)) {
         g_assert_not_reached();
     }
+
+    s->data_cond_signal = false;
+
     g_mutex_unlock(&s->data_mutex);
 }
 
@@ -72,6 +77,10 @@ void *tpm_emu_ctrl_thread(void *data)
     QIOChannel *ioc;
 
     qio_channel_socket_listen_sync(lioc, s->addr, &error_abort);
+
+    g_mutex_lock(&s->data_mutex);
+    s->data_cond_signal = true;
+    g_mutex_unlock(&s->data_mutex);
     g_cond_signal(&s->data_cond);
 
     qio_channel_wait(QIO_CHANNEL(lioc), G_IO_IN);
diff --git a/tests/tpm-emu.h b/tests/tpm-emu.h
index ef4bfa8800..09fcf72bde 100644
--- a/tests/tpm-emu.h
+++ b/tests/tpm-emu.h
@@ -26,6 +26,7 @@ struct tpm_hdr {
 typedef struct TestState {
     CompatGMutex data_mutex;
     CompatGCond data_cond;
+    bool data_cond_signal;
     SocketAddress *addr;
     QIOChannel *tpm_ioc;
     GThread *emu_tpm_thread;
diff --git a/tests/tpm-tis-test.c b/tests/tpm-tis-test.c
index 14754d9706..c8ec14888f 100644
--- a/tests/tpm-tis-test.c
+++ b/tests/tpm-tis-test.c
@@ -446,6 +446,7 @@ int main(int argc, char **argv)
     test.addr->u.q_unix.path = g_build_filename(tmp_path, "sock", NULL);
     g_mutex_init(&test.data_mutex);
     g_cond_init(&test.data_cond);
+    test.data_cond_signal = false;
 
     thread = g_thread_new(NULL, tpm_emu_ctrl_thread, &test);
     tpm_emu_test_wait_cond(&test);
-- 
2.14.4