@@ -382,6 +382,7 @@ static void cpu_handle_debug_exception(CPUState *cpu)
/* main execution loop */
volatile sig_atomic_t exit_request;
+CPUState *tcg_current_cpu;
int cpu_exec(CPUState *cpu)
{
@@ -405,15 +406,7 @@ int cpu_exec(CPUState *cpu)
}
current_cpu = cpu;
-
- /* As long as current_cpu is null, up to the assignment just above,
- * requests by other threads to exit the execution loop are expected to
- * be issued using the exit_request global. We must make sure that our
- * evaluation of the global value is performed past the current_cpu
- * value transition point, which requires a memory barrier as well as
- * an instruction scheduling constraint on modern architectures. */
- smp_mb();
-
+ atomic_mb_set(&tcg_current_cpu, cpu);
rcu_read_lock();
if (unlikely(exit_request)) {
@@ -614,5 +607,8 @@ int cpu_exec(CPUState *cpu)
/* fail safe : never use current_cpu outside cpu_exec() */
current_cpu = NULL;
+
+ /* Does not need atomic_mb_set because a spurious wakeup is okay. */
+ atomic_set(&tcg_current_cpu, NULL);
return ret;
}
@@ -663,8 +663,9 @@ static void cpu_handle_guest_debug(CPUState *cpu)
static void cpu_signal(int sig)
{
- if (current_cpu) {
- cpu_exit(current_cpu);
+ CPUState *cpu = atomic_mb_read(&tcg_current_cpu);
+ if (cpu) {
+ cpu_exit(cpu);
}
exit_request = 1;
}
@@ -346,6 +346,7 @@ tb_page_addr_t get_page_addr_code(CPUArchState *env1, target_ulong addr);
extern int singlestep;
/* cpu-exec.c */
+extern CPUState *tcg_current_cpu;
extern volatile sig_atomic_t exit_request;
#endif
This is already useful on Windows in order to remove tls.h, because accesses to current_cpu are done from a different thread on that platform. It will be used on POSIX platforms as soon TCG stops using signals to interrupt the execution of translated code. Signed-off-by: Paolo Bonzini <pbonzini@redhat.com> --- cpu-exec.c | 14 +++++--------- cpus.c | 5 +++-- include/exec/exec-all.h | 1 + 3 files changed, 9 insertions(+), 11 deletions(-)