Synchronize the remaining pair of accesses in cpu_signal. The
wrongly-ordered accesses in cpu_signal are currently not an issue on
Windows because they execute atomically between SuspendProcess and
ResumeProcess. Only cpu_exec can be split (and the newly introduced
atomic_mb_read would be needed on Windows too, but the compiler
must not be doing strange optimizations).
Signed-off-by: Paolo Bonzini <pbonz...@redhat.com>
---
cpu-exec.c | 2 +-
cpus.c | 14 ++++++++++----
2 files changed, 11 insertions(+), 5 deletions(-)
diff --git a/cpu-exec.c b/cpu-exec.c
index 2128bf1..b337506 100644
--- a/cpu-exec.c
+++ b/cpu-exec.c
@@ -409,7 +409,7 @@ int cpu_exec(CPUState *cpu)
atomic_mb_set(&tcg_current_cpu, cpu);
rcu_read_lock();
- if (unlikely(exit_request)) {
+ if (unlikely(atomic_mb_read(&exit_request))) {
cpu->exit_request = 1;
}
diff --git a/cpus.c b/cpus.c
index ec8168c..783ef00 100644
--- a/cpus.c
+++ b/cpus.c
@@ -663,11 +663,15 @@ static void cpu_handle_guest_debug(CPUState *cpu)
static void cpu_signal(int sig)
{
- CPUState *cpu = atomic_mb_read(&tcg_current_cpu);
+ CPUState *cpu;
+ /* Ensure whatever caused the exit has reached the CPU threads before
+ * writing exit_request.
+ */
+ atomic_mb_set(&exit_request, 1);
+ cpu = atomic_mb_read(&tcg_current_cpu);
if (cpu) {
cpu_exit(cpu);
}
- exit_request = 1;
}
#ifdef CONFIG_LINUX
@@ -1074,7 +1078,7 @@ static void *qemu_tcg_cpu_thread_fn(void *arg)
}
/* process any pending work */
- exit_request = 1;
+ atomic_mb_set(&exit_request, 1);
while (1) {
tcg_exec_all();
@@ -1453,7 +1457,9 @@ static void tcg_exec_all(void)
break;
}
}
- exit_request = 0;
+
+ /* Pairs with smp_wmb in qemu_cpu_kick. */
+ atomic_mb_set(&exit_request, 0);
}
void list_cpus(FILE *f, fprintf_function cpu_fprintf, const char *optarg)
--
2.4.3
