Booting an s390x VM in record/replay mode hangs due to a deadlock
between rr_cpu_thread_fn() and s390_machine_reset(). The former needs
the record/replay mutex held by the latter, and the latter waits until
the former completes its run_on_cpu() request.
Fix by temporarily dropping the record/replay mutex, like it's done in
pause_all_vcpus().
Signed-off-by: Ilya Leoshkevich <i...@linux.ibm.com>
---
hw/s390x/s390-virtio-ccw.c | 24 +++++++++++++++++++++++-
1 file changed, 23 insertions(+), 1 deletion(-)
diff --git a/hw/s390x/s390-virtio-ccw.c b/hw/s390x/s390-virtio-ccw.c
index 38aeba14eeb..e2386910f78 100644
--- a/hw/s390x/s390-virtio-ccw.c
+++ b/hw/s390x/s390-virtio-ccw.c
@@ -48,6 +48,7 @@
#include "kvm/kvm_s390x.h"
#include "hw/virtio/virtio-md-pci.h"
#include "hw/s390x/virtio-ccw-md.h"
+#include "system/replay.h"
#include CONFIG_DEVICES
static Error *pv_mig_blocker;
@@ -454,6 +455,18 @@ static void s390_machine_reset(MachineState *machine,
ResetType type)
CPUState *cs, *t;
S390CPU *cpu;
+ /*
+ * Temporarily drop the record/replay mutex to let rr_cpu_thread_fn()
+ * process the run_on_cpu() requests below. This is safe, because at this
+ * point one of the following is true:
+ * - All CPU threads are not running, either because the machine is being
+ * initialized, or because the guest requested a reset using diag 308.
+ * There is no risk to desync the record/replay state.
+ * - A snapshot is about to be loaded. The record/replay state consistency
+ * is not important.
+ */
+ replay_mutex_unlock();
+
/* get the reset parameters, reset them once done */
s390_ipl_get_reset_request(&cs, &reset_type);
@@ -533,7 +546,7 @@ static void s390_machine_reset(MachineState *machine,
ResetType type)
* went wrong.
*/
s390_cpu_set_state(S390_CPU_STATE_OPERATING, cpu);
- return;
+ goto out_lock;
}
run_on_cpu(cs, s390_do_cpu_load_normal, RUN_ON_CPU_NULL);
@@ -546,6 +559,15 @@ static void s390_machine_reset(MachineState *machine,
ResetType type)
run_on_cpu(t, s390_do_cpu_set_diag318, RUN_ON_CPU_HOST_ULONG(0));
}
s390_ipl_clear_reset_request();
+
+out_lock:
+ /*
+ * Re-take the record/replay mutex, temporarily dropping the BQL in order
+ * to satisfy the ordering requirements.
+ */
+ bql_unlock();
+ replay_mutex_lock();
+ bql_lock();
}
static void s390_machine_device_pre_plug(HotplugHandler *hotplug_dev,
--
2.48.1
