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cpus-common: Introduce async_safe_run_on_cpu()

Reviewed-by: Richard Henderson <rth@twiddle.net>
Reviewed-by: Alex Bennée <alex.bennee@linaro.org>
Signed-off-by: Paolo Bonzini <pbonzini@redhat.com>
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bonzini committed Aug 28, 2016
1 parent 758e1b2 commit 53f5ed95064fe6807890cd5535445a05d3361bd2
Showing with 45 additions and 2 deletions.
  1. +31 −2 cpus-common.c
  2. +14 −0 include/qom/cpu.h
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@@ -18,6 +18,7 @@
*/
#include "qemu/osdep.h"
#include "qemu/main-loop.h"
#include "exec/cpu-common.h"
#include "qom/cpu.h"
#include "sysemu/cpus.h"
@@ -106,7 +107,7 @@ struct qemu_work_item {
struct qemu_work_item *next;
run_on_cpu_func func;
void *data;
bool free, done;
bool free, exclusive, done;
};
static void queue_work_on_cpu(CPUState *cpu, struct qemu_work_item *wi)
@@ -139,6 +140,7 @@ void do_run_on_cpu(CPUState *cpu, run_on_cpu_func func, void *data,
wi.data = data;
wi.done = false;
wi.free = false;
wi.exclusive = false;
queue_work_on_cpu(cpu, &wi);
while (!atomic_mb_read(&wi.done)) {
@@ -229,6 +231,19 @@ void cpu_exec_end(CPUState *cpu)
qemu_mutex_unlock(&qemu_cpu_list_lock);
}
void async_safe_run_on_cpu(CPUState *cpu, run_on_cpu_func func, void *data)
{
struct qemu_work_item *wi;
wi = g_malloc0(sizeof(struct qemu_work_item));
wi->func = func;
wi->data = data;
wi->free = true;
wi->exclusive = true;
queue_work_on_cpu(cpu, wi);
}
void process_queued_cpu_work(CPUState *cpu)
{
struct qemu_work_item *wi;
@@ -245,7 +260,21 @@ void process_queued_cpu_work(CPUState *cpu)
cpu->queued_work_last = NULL;
}
qemu_mutex_unlock(&cpu->work_mutex);
wi->func(cpu, wi->data);
if (wi->exclusive) {
/* Running work items outside the BQL avoids the following deadlock:
* 1) start_exclusive() is called with the BQL taken while another
* CPU is running; 2) cpu_exec in the other CPU tries to takes the
* BQL, so it goes to sleep; start_exclusive() is sleeping too, so
* neither CPU can proceed.
*/
qemu_mutex_unlock_iothread();
start_exclusive();
wi->func(cpu, wi->data);
end_exclusive();
qemu_mutex_lock_iothread();
} else {
wi->func(cpu, wi->data);
}
qemu_mutex_lock(&cpu->work_mutex);
if (wi->free) {
g_free(wi);
View
@@ -655,6 +655,20 @@ void run_on_cpu(CPUState *cpu, run_on_cpu_func func, void *data);
*/
void async_run_on_cpu(CPUState *cpu, run_on_cpu_func func, void *data);
/**
* async_safe_run_on_cpu:
* @cpu: The vCPU to run on.
* @func: The function to be executed.
* @data: Data to pass to the function.
*
* Schedules the function @func for execution on the vCPU @cpu asynchronously,
* while all other vCPUs are sleeping.
*
* Unlike run_on_cpu and async_run_on_cpu, the function is run outside the
* BQL.
*/
void async_safe_run_on_cpu(CPUState *cpu, run_on_cpu_func func, void *data);
/**
* qemu_get_cpu:
* @index: The CPUState@cpu_index value of the CPU to obtain.

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