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Re: [Qemu-devel] [PATCH v8 07/25] tcg: rename tcg_current_cpu to tcg_cur
From: |
Pranith Kumar |
Subject: |
Re: [Qemu-devel] [PATCH v8 07/25] tcg: rename tcg_current_cpu to tcg_current_rr_cpu |
Date: |
Sun, 29 Jan 2017 16:04:32 -0500 |
User-agent: |
mu4e 0.9.17; emacs 25.1.1 |
Alex Bennée writes:
> ..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 <address@hidden>
> Reviewed-by: Richard Henderson <address@hidden>
> ---
> v4:
> - keep global exit_request setting for now
> - fix merge conflicts
> v5:
> - merge conflicts with kick changes
> ---
> cpu-exec-common.c | 1 -
> cpu-exec.c | 3 ---
> cpus.c | 41 ++++++++++++++++++++++-------------------
> include/exec/exec-all.h | 1 -
> 4 files changed, 22 insertions(+), 24 deletions(-)
>
> diff --git a/cpu-exec-common.c b/cpu-exec-common.c
> index 767d9c6f0c..e2bc053372 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;
>
> /* exit the current TB, but without causing any exception to be raised */
> void cpu_loop_exit_noexc(CPUState *cpu)
> diff --git a/cpu-exec.c b/cpu-exec.c
> index 1b8685dc21..f9e836c8dd 100644
> --- a/cpu-exec.c
> +++ b/cpu-exec.c
> @@ -609,7 +609,6 @@ 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))) {
> @@ -668,7 +667,5 @@ 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 a98925105c..6d64199831 100644
> --- a/cpus.c
> +++ b/cpus.c
> @@ -779,8 +779,7 @@ 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)
>
> @@ -789,10 +788,23 @@ 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)
> @@ -812,7 +824,6 @@ static void stop_tcg_kick_timer(void)
> }
> }
>
> -
> /***********************************************************/
> void hw_error(const char *fmt, ...)
> {
> @@ -1323,6 +1334,7 @@ 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);
> @@ -1342,6 +1354,8 @@ 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);
> @@ -1420,24 +1434,13 @@ 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()) {
> /*
> @@ -1485,7 +1488,7 @@ 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 bbc9478a50..3cbd359dd7 100644
> --- a/include/exec/exec-all.h
> +++ b/include/exec/exec-all.h
> @@ -404,7 +404,6 @@ 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
Reviewed-by: Pranith Kumar <address@hidden>
--
Pranith
- [Qemu-devel] [PATCH v8 00/25] Remaining MTTCG Base patches and ARM enablement, Alex Bennée, 2017/01/27
- [Qemu-devel] [PATCH v8 02/25] mttcg: translate-all: Enable locking debug in a debug build, Alex Bennée, 2017/01/27
- [Qemu-devel] [PATCH v8 04/25] tcg: move TCG_MO/BAR types into own file, Alex Bennée, 2017/01/27
- [Qemu-devel] [PATCH v8 07/25] tcg: rename tcg_current_cpu to tcg_current_rr_cpu, Alex Bennée, 2017/01/27
- Re: [Qemu-devel] [PATCH v8 07/25] tcg: rename tcg_current_cpu to tcg_current_rr_cpu,
Pranith Kumar <=
- [Qemu-devel] [PATCH v8 01/25] docs: new design document multi-thread-tcg.txt, Alex Bennée, 2017/01/27
- [Qemu-devel] [PATCH v8 03/25] mttcg: Add missing tb_lock/unlock() in cpu_exec_step(), Alex Bennée, 2017/01/27
- [Qemu-devel] [PATCH v8 05/25] tcg: add options for enabling MTTCG, Alex Bennée, 2017/01/27
- [Qemu-devel] [PATCH v8 15/25] cputlb: introduce tlb_flush_* async work., Alex Bennée, 2017/01/27
- [Qemu-devel] [PATCH v8 10/25] tcg: enable tb_lock() for SoftMMU, Alex Bennée, 2017/01/27
- [Qemu-devel] [PATCH v8 11/25] tcg: enable thread-per-vCPU, Alex Bennée, 2017/01/27