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tcg: rename tcg_current_cpu to tcg_current_rr_cpu

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..and make the definition local to cpus. In preparation for MTTCG the
concept of a global tcg_current_cpu will no longer make sense. However
we still need to keep track of it in the single-threaded case to be able
to exit quickly when required.

qemu_cpu_kick_no_halt() moves and becomes qemu_cpu_kick_rr_cpu() to
emphasise its use-case. qemu_cpu_kick now kicks the relevant cpu as
well as qemu_kick_rr_cpu() which will become a no-op in MTTCG.

For the time being the setting of the global exit_request remains.

Signed-off-by: Alex Bennée <alex.bennee@linaro.org>
Reviewed-by: Richard Henderson <rth@twiddle.net>
Reviewed-by: Pranith Kumar <bobby.prani@gmail.com>
This commit is contained in:
Alex Bennée 2017-02-23 18:29:10 +00:00
parent 6546706d28
commit 791158d93b
4 changed files with 22 additions and 24 deletions
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1
cpu-exec-common.c
View File

@ -24,7 +24,6 @@
#include "exec/memory-internal.h"
bool exit_request;
CPUState *tcg_current_cpu;
/* exit the current TB, but without causing any exception to be raised */
void cpu_loop_exit_noexc(CPUState *cpu)

3
cpu-exec.c
View File

@ -612,7 +612,6 @@ int cpu_exec(CPUState *cpu)
return EXCP_HALTED;
}
atomic_mb_set(&tcg_current_cpu, cpu);
rcu_read_lock();
if (unlikely(atomic_mb_read(&exit_request))) {
@ -666,7 +665,5 @@ 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;
}

41
cpus.c
View File

@ -780,8 +780,7 @@ void configure_icount(QemuOpts *opts, Error **errp)
*/
static QEMUTimer *tcg_kick_vcpu_timer;
static void qemu_cpu_kick_no_halt(void);
static CPUState *tcg_current_rr_cpu;
#define TCG_KICK_PERIOD (NANOSECONDS_PER_SECOND / 10)
@ -790,10 +789,23 @@ static inline int64_t qemu_tcg_next_kick(void)
return qemu_clock_get_ns(QEMU_CLOCK_VIRTUAL) + TCG_KICK_PERIOD;
}
/* Kick the currently round-robin scheduled vCPU */
static void qemu_cpu_kick_rr_cpu(void)
{
CPUState *cpu;
atomic_mb_set(&exit_request, 1);
do {
cpu = atomic_mb_read(&tcg_current_rr_cpu);
if (cpu) {
cpu_exit(cpu);
}
} while (cpu != atomic_mb_read(&tcg_current_rr_cpu));
}
static void kick_tcg_thread(void *opaque)
{
timer_mod(tcg_kick_vcpu_timer, qemu_tcg_next_kick());
qemu_cpu_kick_no_halt();
qemu_cpu_kick_rr_cpu();
}
static void start_tcg_kick_timer(void)
@ -813,7 +825,6 @@ static void stop_tcg_kick_timer(void)
}
}
/***********************************************************/
void hw_error(const char *fmt, ...)
{
@ -1324,6 +1335,7 @@ static void *qemu_tcg_cpu_thread_fn(void *arg)
}
for (; cpu != NULL && !exit_request; cpu = CPU_NEXT(cpu)) {
atomic_mb_set(&tcg_current_rr_cpu, cpu);
qemu_clock_enable(QEMU_CLOCK_VIRTUAL,
(cpu->singlestep_enabled & SSTEP_NOTIMER) == 0);
@ -1343,6 +1355,8 @@ static void *qemu_tcg_cpu_thread_fn(void *arg)
}
} /* for cpu.. */
/* Does not need atomic_mb_set because a spurious wakeup is okay. */
atomic_set(&tcg_current_rr_cpu, NULL);
/* Pairs with smp_wmb in qemu_cpu_kick. */
atomic_mb_set(&exit_request, 0);
@ -1421,24 +1435,13 @@ static void qemu_cpu_kick_thread(CPUState *cpu)
#endif
}
static void qemu_cpu_kick_no_halt(void)
{
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);
}
}
void qemu_cpu_kick(CPUState *cpu)
{
qemu_cond_broadcast(cpu->halt_cond);
if (tcg_enabled()) {
qemu_cpu_kick_no_halt();
cpu_exit(cpu);
/* Also ensure current RR cpu is kicked */
qemu_cpu_kick_rr_cpu();
} else {
if (hax_enabled()) {
/*
@ -1486,7 +1489,7 @@ void qemu_mutex_lock_iothread(void)
atomic_dec(&iothread_requesting_mutex);
} else {
if (qemu_mutex_trylock(&qemu_global_mutex)) {
qemu_cpu_kick_no_halt();
qemu_cpu_kick_rr_cpu();
qemu_mutex_lock(&qemu_global_mutex);
}
atomic_dec(&iothread_requesting_mutex);

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

@ -405,7 +405,6 @@ bool memory_region_is_unassigned(MemoryRegion *mr);
extern int singlestep;
/* cpu-exec.c, accessed with atomic_mb_read/atomic_mb_set */
extern CPUState *tcg_current_cpu;
extern bool exit_request;
#endif