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tcg: introduce tcg_current_cpu 

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.

Reviewed-by: Richard Henderson <rth@twiddle.net>
Signed-off-by: Paolo Bonzini <pbonzini@redhat.com>
This commit is contained in:
Paolo Bonzini 2015-08-18 06:24:34 -07:00
parent 5039d6e235
commit 9373e63297
3 changed files with 9 additions and 11 deletions
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14
cpu-exec.c
View File

@ -342,6 +342,7 @@ static void cpu_handle_debug_exception(CPUState *cpu)
/* main execution loop */ /* main execution loop */
volatile sig_atomic_t exit_request; volatile sig_atomic_t exit_request;
CPUState *tcg_current_cpu;
int cpu_exec(CPUState *cpu) int cpu_exec(CPUState *cpu)
{ {
@ -368,15 +369,7 @@ int cpu_exec(CPUState *cpu)
} }
current_cpu = cpu; current_cpu = cpu;
atomic_mb_set(&tcg_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();
rcu_read_lock(); rcu_read_lock();
if (unlikely(exit_request)) { if (unlikely(exit_request)) {
@ -579,5 +572,8 @@ int cpu_exec(CPUState *cpu)
/* fail safe : never use current_cpu outside cpu_exec() */ /* fail safe : never use current_cpu outside cpu_exec() */
current_cpu = NULL; current_cpu = NULL;
/* Does not need atomic_mb_set because a spurious wakeup is okay. */
atomic_set(&tcg_current_cpu, NULL);
return ret; return ret;
} }

5
cpus.c
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@ -663,8 +663,9 @@ static void cpu_handle_guest_debug(CPUState *cpu)
static void cpu_signal(int sig) static void cpu_signal(int sig)
{ {
if (current_cpu) { CPUState *cpu = atomic_mb_read(&tcg_current_cpu);
cpu_exit(current_cpu); if (cpu) {
cpu_exit(cpu);
} }
exit_request = 1; exit_request = 1;
} }

1
include/exec/exec-all.h
View File

@ -387,6 +387,7 @@ tb_page_addr_t get_page_addr_code(CPUArchState *env1, target_ulong addr);
extern int singlestep; extern int singlestep;
/* cpu-exec.c */ /* cpu-exec.c */
extern CPUState *tcg_current_cpu;
extern volatile sig_atomic_t exit_request; extern volatile sig_atomic_t exit_request;
#if !defined(CONFIG_USER_ONLY) #if !defined(CONFIG_USER_ONLY)