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Re: [Qemu-devel] [PATCH 07/16] cpus-common: move CPU work item managemen
From: |
Emilio G. Cota |
Subject: |
Re: [Qemu-devel] [PATCH 07/16] cpus-common: move CPU work item management to common code |
Date: |
Wed, 21 Sep 2016 13:03:34 -0400 |
User-agent: |
Mutt/1.5.23 (2014-03-12) |
On Mon, Sep 19, 2016 at 14:50:50 +0200, Paolo Bonzini wrote:
> From: Sergey Fedorov <address@hidden>
>
> Make CPU work core functions common between system and user-mode
> emulation. User-mode does not use run_on_cpu, so do not implement it.
>
> Signed-off-by: Sergey Fedorov <address@hidden>
> Signed-off-by: Sergey Fedorov <address@hidden>
> Reviewed-by: Alex Bennée <address@hidden>
> Signed-off-by: Alex Bennée <address@hidden>
> Message-Id: <address@hidden>
> Signed-off-by: Paolo Bonzini <address@hidden>
> ---
> bsd-user/main.c | 11 +++++--
> cpus-common.c | 94
> +++++++++++++++++++++++++++++++++++++++++++++++++++++++
> cpus.c | 82 +-----------------------------------------------
> include/qom/cpu.h | 27 +++++++++++-----
> linux-user/main.c | 25 +++++++++++++++
> 5 files changed, 148 insertions(+), 91 deletions(-)
>
> diff --git a/bsd-user/main.c b/bsd-user/main.c
> index 591c424..6dfa912 100644
> --- a/bsd-user/main.c
> +++ b/bsd-user/main.c
> @@ -68,11 +68,11 @@ int cpu_get_pic_interrupt(CPUX86State *env)
> #endif
>
> /* These are no-ops because we are not threadsafe. */
> -static inline void cpu_exec_start(CPUArchState *env)
> +static inline void cpu_exec_start(CPUState *cpu)
> {
> }
>
> -static inline void cpu_exec_end(CPUArchState *env)
> +static inline void cpu_exec_end(CPUState *cpu)
> {
> }
>
> @@ -164,7 +164,11 @@ void cpu_loop(CPUX86State *env)
> //target_siginfo_t info;
>
> for(;;) {
> + cpu_exec_start(cs);
> trapnr = cpu_exec(cs);
> + cpu_exec_end(cs);
> + process_queued_cpu_work(cs);
> +
> switch(trapnr) {
> case 0x80:
> /* syscall from int $0x80 */
> @@ -505,7 +509,10 @@ void cpu_loop(CPUSPARCState *env)
> //target_siginfo_t info;
>
> while (1) {
> + cpu_exec_start(cs);
> trapnr = cpu_exec(cs);
> + cpu_exec_end(cs);
> + process_queued_cpu_work(cs);
>
> switch (trapnr) {
> #ifndef TARGET_SPARC64
> diff --git a/cpus-common.c b/cpus-common.c
> index ca367ad..a739e66 100644
> --- a/cpus-common.c
> +++ b/cpus-common.c
> @@ -23,10 +23,12 @@
> #include "sysemu/cpus.h"
>
> static QemuMutex qemu_cpu_list_mutex;
> +static QemuCond qemu_work_cond;
>
> void qemu_init_cpu_list(void)
> {
> qemu_mutex_init(&qemu_cpu_list_mutex);
> + qemu_cond_init(&qemu_work_cond);
> }
>
> void cpu_list_lock(void)
> @@ -81,3 +83,95 @@ void cpu_list_remove(CPUState *cpu)
> cpu->cpu_index = UNASSIGNED_CPU_INDEX;
> qemu_mutex_unlock(&qemu_cpu_list_mutex);
> }
> +
> +struct qemu_work_item {
> + struct qemu_work_item *next;
> + run_on_cpu_func func;
> + void *data;
> + int done;
> + bool free;
> +};
> +
> +static void queue_work_on_cpu(CPUState *cpu, struct qemu_work_item *wi)
> +{
> + qemu_mutex_lock(&cpu->work_mutex);
> + if (cpu->queued_work_first == NULL) {
> + cpu->queued_work_first = wi;
> + } else {
> + cpu->queued_work_last->next = wi;
> + }
> + cpu->queued_work_last = wi;
> + wi->next = NULL;
> + wi->done = false;
> + qemu_mutex_unlock(&cpu->work_mutex);
> +
> + qemu_cpu_kick(cpu);
> +}
> +
> +void do_run_on_cpu(CPUState *cpu, run_on_cpu_func func, void *data,
> + QemuMutex *mutex)
> +{
> + struct qemu_work_item wi;
> +
> + if (qemu_cpu_is_self(cpu)) {
> + func(cpu, data);
> + return;
> + }
> +
> + wi.func = func;
> + wi.data = data;
> + wi.free = false;
> +
> + queue_work_on_cpu(cpu, &wi);
> + while (!atomic_mb_read(&wi.done)) {
> + CPUState *self_cpu = current_cpu;
> +
> + qemu_cond_wait(&qemu_work_cond, mutex);
> + current_cpu = self_cpu;
> + }
> +}
(snip)
> diff --git a/cpus.c b/cpus.c
> index 28d6206..c3afd18 100644
> --- a/cpus.c
> +++ b/cpus.c
(snip)
> void run_on_cpu(CPUState *cpu, run_on_cpu_func func, void *data)
> {
> - struct qemu_work_item wi;
> -
> - if (qemu_cpu_is_self(cpu)) {
> - func(cpu, data);
> - return;
> - }
> -
> - wi.func = func;
> - wi.data = data;
> - wi.free = false;
> -
> - queue_work_on_cpu(cpu, &wi);
> - while (!atomic_mb_read(&wi.done)) {
> - CPUState *self_cpu = current_cpu;
> -
> - qemu_cond_wait(&qemu_work_cond, &qemu_global_mutex);
> - current_cpu = self_cpu;
> - }
> -}
> -
> -void async_run_on_cpu(CPUState *cpu, run_on_cpu_func func, void *data)
> -{
> - struct qemu_work_item *wi;
> -
> - if (qemu_cpu_is_self(cpu)) {
> - func(cpu, data);
> - return;
> - }
> -
> - wi = g_malloc0(sizeof(struct qemu_work_item));
> - wi->func = func;
> - wi->data = data;
> - wi->free = true;
> -
> - queue_work_on_cpu(cpu, wi);
> + do_run_on_cpu(cpu, func, data, &qemu_global_mutex);
> }
AFAICT this is the only caller of do_run_on_cpu. Is qemu_global_mutex
necessary here? I wonder if we could just use cpu->work_mutex to wait
on a per-cpu work_cond. Contending for a global lock here doesn't
make much sense unless I'm missing something. Furthermore, that change
would allow us to get rid of the atomic accesses to wi.done, which I
dislike.
E.
- Re: [Qemu-devel] [PATCH v7 00/16] cpu-exec: Safe work in quiescent state, (continued)
- [Qemu-devel] [PATCH 06/16] cpus-common: move CPU list management to common code, Paolo Bonzini, 2016/09/19
- [Qemu-devel] [PATCH 08/16] cpus-common: fix uninitialized variable use in run_on_cpu, Paolo Bonzini, 2016/09/19
- [Qemu-devel] [PATCH 09/16] cpus-common: move exclusive work infrastructure from linux-user, Paolo Bonzini, 2016/09/19
- [Qemu-devel] [PATCH 10/16] docs: include formal model for TCG exclusive sections, Paolo Bonzini, 2016/09/19
- [Qemu-devel] [PATCH 11/16] cpus-common: always defer async_run_on_cpu work items, Paolo Bonzini, 2016/09/19
- [Qemu-devel] [PATCH 12/16] cpus-common: remove redundant call to exclusive_idle(), Paolo Bonzini, 2016/09/19
- [Qemu-devel] [PATCH 13/16] cpus-common: simplify locking for start_exclusive/end_exclusive, Paolo Bonzini, 2016/09/19