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[Qemu-devel] [RFC PATCH v1 5/9] replay: make locking visible outside rep
From: |
Alex Bennée |
Subject: |
[Qemu-devel] [RFC PATCH v1 5/9] replay: make locking visible outside replay code |
Date: |
Fri, 5 May 2017 11:38:18 +0100 |
The replay_mutex_lock/unlock/locked functions are now going to be used
for ensuring lock-step behaviour between the two threads. Make them
public API functions and also provide stubs for non-QEMU builds on
common paths.
Signed-off-by: Alex Bennée <address@hidden>
---
include/sysemu/replay.h | 14 ++++++++++++++
replay/replay-internal.c | 5 ++---
replay/replay-internal.h | 5 ++---
stubs/replay.c | 15 +++++++++++++++
4 files changed, 33 insertions(+), 6 deletions(-)
diff --git a/include/sysemu/replay.h b/include/sysemu/replay.h
index f1c0712795..08bffa2dc2 100644
--- a/include/sysemu/replay.h
+++ b/include/sysemu/replay.h
@@ -46,6 +46,20 @@ extern ReplayMode replay_mode;
/* Name of the initial VM snapshot */
extern char *replay_snapshot;
+/* Replay locking
+ *
+ * The locks are needed to protect the shared structures and log file
+ * when doing record/replay. They also are the main sync-point between
+ * the main-loop thread and the vCPU thread. This was a role
+ * previously filled by the BQL which has been busy trying to reduce
+ * its impact across the code. This ensures blocks of events stay
+ * sequential and reproducible.
+ */
+
+void replay_mutex_lock(void);
+void replay_mutex_unlock(void);
+bool replay_mutex_locked(void);
+
/* Replay process control functions */
/*! Enables recording or saving event log with specified parameters */
diff --git a/replay/replay-internal.c b/replay/replay-internal.c
index 157c863e25..e6b2fdb6c1 100644
--- a/replay/replay-internal.c
+++ b/replay/replay-internal.c
@@ -181,7 +181,7 @@ void replay_mutex_destroy(void)
static __thread bool replay_locked;
-static bool replay_mutex_locked(void)
+bool replay_mutex_locked(void)
{
return replay_locked;
}
@@ -204,7 +204,7 @@ void replay_mutex_unlock(void)
void replay_save_instructions(void)
{
if (replay_file && replay_mode == REPLAY_MODE_RECORD) {
- replay_mutex_lock();
+ g_assert(replay_mutex_locked());
int diff = (int)(replay_get_current_step() -
replay_state.current_step);
/* Time can only go forward */
@@ -215,6 +215,5 @@ void replay_save_instructions(void)
replay_put_dword(diff);
replay_state.current_step += diff;
}
- replay_mutex_unlock();
}
}
diff --git a/replay/replay-internal.h b/replay/replay-internal.h
index ed66ed803c..b0cf78f16f 100644
--- a/replay/replay-internal.h
+++ b/replay/replay-internal.h
@@ -97,12 +97,11 @@ int64_t replay_get_qword(void);
void replay_get_array(uint8_t *buf, size_t *size);
void replay_get_array_alloc(uint8_t **buf, size_t *size);
-/* Mutex functions for protecting replay log file */
+/* Mutex functions for protecting replay log file and ensuring
+ * synchronisation between vCPU and main-loop threads. */
void replay_mutex_init(void);
void replay_mutex_destroy(void);
-void replay_mutex_lock(void);
-void replay_mutex_unlock(void);
/*! Checks error status of the file. */
void replay_check_error(void);
diff --git a/stubs/replay.c b/stubs/replay.c
index 9c8aa48c9c..39c5746043 100644
--- a/stubs/replay.c
+++ b/stubs/replay.c
@@ -72,3 +72,18 @@ uint64_t blkreplay_next_id(void)
{
return 0;
}
+
+void replay_mutex_lock(void)
+{
+ abort();
+}
+
+void replay_mutex_unlock(void)
+{
+ abort();
+}
+
+bool replay_mutex_locked(void)
+{
+ return false;
+}
--
2.11.0
- [Qemu-devel] [RFC PATCH v1 0/9] BQL and Replay Lock changes, Alex Bennée, 2017/05/05
- [Qemu-devel] [RFC PATCH v1 1/9] target/arm/arm-powertctl: drop BQL assertions, Alex Bennée, 2017/05/05
- [Qemu-devel] [RFC PATCH v1 5/9] replay: make locking visible outside replay code,
Alex Bennée <=
- [Qemu-devel] [RFC PATCH v1 2/9] cpus: push BQL lock to qemu_*_wait_io_event, Alex Bennée, 2017/05/05
- [Qemu-devel] [RFC PATCH v1 3/9] cpus: only take BQL for sleeping threads, Alex Bennée, 2017/05/05
- [Qemu-devel] [RFC PATCH v1 4/9] replay/replay-internal.c: track holding of replay_lock, Alex Bennée, 2017/05/05
- [Qemu-devel] [RFC PATCH v1 8/9] util/qemu-thread-*: add qemu_lock, locked and unlock trace events, Alex Bennée, 2017/05/05