We have had some tracing tools for mutex but it's not easy to use them
for e.g. dead locks. Let's provide "--enable-debug-mutex" parameter
when configure to allow QemuMutex to store the last owner that took
specific lock. It will be easy to use this tool to debug deadlocks
since we can directly know who took the lock then as long as we can have
a debugger attached to the process.
Signed-off-by: Peter Xu <pet...@redhat.com>
---
configure | 10 ++++++++++
include/qemu/thread-posix.h | 4 ++++
include/qemu/thread-win32.h | 4 ++++
util/qemu-thread-common.h | 12 ++++++++++++
4 files changed, 30 insertions(+)
diff --git a/configure b/configure
index 0a19b033bc..a80af735b2 100755
--- a/configure
+++ b/configure
@@ -451,6 +451,7 @@ jemalloc="no"
replication="yes"
vxhs=""
libxml2=""
+debug_mutex="no"
supported_cpu="no"
supported_os="no"
@@ -1374,6 +1375,10 @@ for opt do
;;
--disable-git-update) git_update=no
;;
+ --enable-debug-mutex) debug_mutex=yes
+ ;;
+ --disable-debug-mutex) debug_mutex=no
+ ;;
*)
echo "ERROR: unknown option $opt"
echo "Try '$0 --help' for more information"
@@ -1631,6 +1636,7 @@ disabled with --disable-FEATURE, default is enabled if
available:
crypto-afalg Linux AF_ALG crypto backend driver
vhost-user vhost-user support
capstone capstone disassembler support
+ debug-mutex mutex debugging support
NOTE: The object files are built at the place where configure is launched
EOF
@@ -5874,6 +5880,7 @@ echo "avx2 optimization $avx2_opt"
echo "replication support $replication"
echo "VxHS block device $vxhs"
echo "capstone $capstone"
+echo "mutex debugging $debug_mutex"
if test "$sdl_too_old" = "yes"; then
echo "-> Your SDL version is too old - please upgrade to have SDL support"
@@ -6602,6 +6609,9 @@ fi
if test "$capstone" != "no" ; then
echo "CONFIG_CAPSTONE=y" >> $config_host_mak
fi
+if test "$debug_mutex" = "yes" ; then
+ echo "CONFIG_DEBUG_MUTEX=y" >> $config_host_mak
+fi
# Hold two types of flag:
# CONFIG_THREAD_SETNAME_BYTHREAD - we've got a way of setting the name on
diff --git a/include/qemu/thread-posix.h b/include/qemu/thread-posix.h
index f3f47e426f..fd27b34128 100644
--- a/include/qemu/thread-posix.h
+++ b/include/qemu/thread-posix.h
@@ -12,6 +12,10 @@ typedef QemuMutex QemuRecMutex;
struct QemuMutex {
pthread_mutex_t lock;
+#ifdef CONFIG_DEBUG_MUTEX
+ const char *file;
+ int line;
+#endif
bool initialized;
};
diff --git a/include/qemu/thread-win32.h b/include/qemu/thread-win32.h
index 3a05e3b3aa..d668d789b4 100644
--- a/include/qemu/thread-win32.h
+++ b/include/qemu/thread-win32.h
@@ -5,6 +5,10 @@
struct QemuMutex {
SRWLOCK lock;
+#ifdef CONFIG_DEBUG_MUTEX
+ const char *file;
+ int line;
+#endif
bool initialized;
};
diff --git a/util/qemu-thread-common.h b/util/qemu-thread-common.h
index 3bf37c9963..f7ec7b9fe3 100644
--- a/util/qemu-thread-common.h
+++ b/util/qemu-thread-common.h
@@ -19,6 +19,10 @@
static inline void qemu_mutex_post_init(QemuMutex *mutex)
{
+#ifdef CONFIG_DEBUG_MUTEX
+ mutex->file = NULL;
+ mutex->line = 0;
+#endif
mutex->initialized = true;
}
@@ -31,12 +35,20 @@ static inline void qemu_mutex_pre_lock(QemuMutex *mutex,
static inline void qemu_mutex_post_lock(QemuMutex *mutex,
const char *file, int line)
{
+#ifdef CONFIG_DEBUG_MUTEX
+ mutex->file = file;
+ mutex->line = line;
+#endif
trace_qemu_mutex_locked(mutex, file, line);
}
static inline void qemu_mutex_pre_unlock(QemuMutex *mutex,
const char *file, int line)
{
+#ifdef CONFIG_DEBUG_MUTEX
+ mutex->file = NULL;
+ mutex->line = 0;
+#endif
trace_qemu_mutex_unlock(mutex, file, line);
}
--
2.14.3
