..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.ben...@linaro.org>
---
v4:
- keep global exit_request setting for now
- fix merge conflicts
---
cpu-exec-common.c | 3 ++-
cpu-exec.c | 3 ---
cpus.c | 41 ++++++++++++++++++++++++-----------------
include/exec/exec-all.h | 1 -
4 files changed, 26 insertions(+), 22 deletions(-)
diff --git a/cpu-exec-common.c b/cpu-exec-common.c
index 0bec55a..e220ba7 100644
--- a/cpu-exec-common.c
+++ b/cpu-exec-common.c
@@ -24,7 +24,6 @@
#include "exec/memory-internal.h"
bool exit_request;
-CPUState *tcg_current_cpu;
int tcg_pending_threads;
/* exit the current TB, but without causing any exception to be raised */
@@ -140,6 +139,7 @@ void run_on_cpu(CPUState *cpu, run_on_cpu_func func, void
*data)
struct qemu_work_item wi;
bool done = false;
+ /* Always true when using tcg RR scheduling from a vCPU context */
if (qemu_cpu_is_self(cpu)) {
func(cpu, data);
return;
@@ -163,6 +163,7 @@ void async_run_on_cpu(CPUState *cpu, run_on_cpu_func func,
void *data)
{
struct qemu_work_item wi;
+ /* Always true when using tcg RR scheduling from a vCPU context */
if (qemu_cpu_is_self(cpu)) {
func(cpu, data);
return;
diff --git a/cpu-exec.c b/cpu-exec.c
index 93a0eb1..42fbf7d 100644
--- a/cpu-exec.c
+++ b/cpu-exec.c
@@ -578,7 +578,6 @@ 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))) {
@@ -637,7 +636,5 @@ 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;
}
diff --git a/cpus.c b/cpus.c
index 8c49d6c..732b21f 100644
--- a/cpus.c
+++ b/cpus.c
@@ -1193,7 +1193,6 @@ static void deal_with_unplugged_cpus(void)
* This is done explicitly rather than relying on side-effects
* elsewhere.
*/
-static void qemu_cpu_kick_no_halt(void);
#define TCG_KICK_PERIOD (NANOSECONDS_PER_SECOND / 10)
@@ -1202,11 +1201,27 @@ static inline int64_t qemu_tcg_next_kick(void)
return qemu_clock_get_ns(QEMU_CLOCK_VIRTUAL) + TCG_KICK_PERIOD;
}
+/* only used in single-thread tcg mode */
+static CPUState *tcg_current_rr_cpu;
+
+/* 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)
{
QEMUTimer *self = *(QEMUTimer **) opaque;
timer_mod(self, qemu_tcg_next_kick());
- qemu_cpu_kick_no_halt();
+ qemu_cpu_kick_rr_cpu();
}
static void *qemu_tcg_cpu_thread_fn(void *arg)
@@ -1257,6 +1272,7 @@ 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);
@@ -1278,6 +1294,8 @@ 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);
@@ -1315,24 +1333,13 @@ 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 {
qemu_cpu_kick_thread(cpu);
}
@@ -1373,7 +1380,7 @@ 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);
diff --git a/include/exec/exec-all.h b/include/exec/exec-all.h
index d73b0e6..3547dfa 100644
--- a/include/exec/exec-all.h
+++ b/include/exec/exec-all.h
@@ -408,7 +408,6 @@ 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 int tcg_pending_threads;
extern bool exit_request;
--
2.7.4
