On 11/10/22 17:48, Emanuele Giuseppe Esposito wrote:
+/*
+ * QEMU accel blocker class
"Lock to inhibit accelerator ioctls"
+ *
+ * Copyright (c) 2014 Red Hat Inc.
2022, you can also add an Author line.
+static int accel_in_ioctls(void)
Return bool (and return early if ret becomes true).
+void accel_ioctl_inhibit_begin(void)
+{
+ CPUState *cpu;
+
+ /*
+ * We allow to inhibit only when holding the BQL, so we can identify
+ * when an inhibitor wants to issue an ioctl easily.
+ */
+ g_assert(qemu_mutex_iothread_locked());
+
+ /* Block further invocations of the ioctls outside the BQL. */
+ CPU_FOREACH(cpu) {
+ qemu_lockcnt_lock(&cpu->in_ioctl_lock);
+ }
+ qemu_lockcnt_lock(&accel_in_ioctl_lock);
+
+ /* Keep waiting until there are running ioctls */
+ while (accel_in_ioctls()) {
+ /* Reset event to FREE. */
+ qemu_event_reset(&accel_in_ioctl_event);
+
+ if (accel_in_ioctls()) {
+
+ CPU_FOREACH(cpu) {
+ /* exit the ioctl */
+ qemu_cpu_kick(cpu);
Only kick if the lockcnt count is > 0? (this is not racy; if it is == 0,
it cannot ever become > 0 again while the lock is taken)
diff --git a/include/sysemu/accel-blocker.h b/include/sysemu/accel-blocker.h
new file mode 100644
index 0000000000..135ebea566
--- /dev/null
+++ b/include/sysemu/accel-blocker.h
@@ -0,0 +1,45 @@
+/*
+ * Accelerator blocking API, to prevent new ioctls from starting and wait the
+ * running ones finish.
+ * This mechanism differs from pause/resume_all_vcpus() in that it does not
+ * release the BQL.
+ *
+ * Copyright (c) 2014 Red Hat Inc.
2022, you can also add an Author line here too.
+ * This work is licensed under the terms of the GNU GPL, version 2 or later.
+ * See the COPYING file in the top-level directory.
+ */
+#ifndef ACCEL_BLOCKER_H
+#define ACCEL_BLOCKER_H
+
+#include "qemu/osdep.h"
+#include "qemu/accel.h"
qemu/accel.h not needed?
+#include "sysemu/cpus.h"
+
+extern void accel_blocker_init(void);
+
+/*
+ * accel_set_in_ioctl/accel_cpu_set_in_ioctl:
+ * Mark when ioctl is about to run or just finished.
+ * If @in_ioctl is true, then mark it is beginning. Otherwise marks that it is
+ * ending.
+ *
+ * These functions will block after accel_ioctl_inhibit_begin() is called,
+ * preventing new ioctls to run. They will continue only after
+ * accel_ioctl_inibith_end().
+ */
+extern void accel_set_in_ioctl(bool in_ioctl);
+extern void accel_cpu_set_in_ioctl(CPUState *cpu, bool in_ioctl);
Why not just
extern void accel_ioctl_begin(void);
extern void accel_ioctl_end(void);
extern void accel_cpu_ioctl_begin(CPUState *cpu);
extern void accel_cpu_ioctl_end(CPUState *cpu);
?
Otherwise it's very nice.
Paolo
