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[Qemu-devel] [PATCH 14/16] cpus-common: Introduce async_safe_run_on_cpu(
From: |
Paolo Bonzini |
Subject: |
[Qemu-devel] [PATCH 14/16] cpus-common: Introduce async_safe_run_on_cpu() |
Date: |
Mon, 19 Sep 2016 14:50:57 +0200 |
We have to run safe work items outside the BQL; for now keep other
work items within the BQL, though this can be changed relatively
easily as a follow-up.
Signed-off-by: Paolo Bonzini <address@hidden>
---
cpus-common.c | 33 +++++++++++++++++++++++++++++++--
include/qom/cpu.h | 14 ++++++++++++++
2 files changed, 45 insertions(+), 2 deletions(-)
diff --git a/cpus-common.c b/cpus-common.c
index 6adc982..f7ad534 100644
--- a/cpus-common.c
+++ b/cpus-common.c
@@ -106,7 +106,7 @@ 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 +139,7 @@ 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)) {
@@ -157,6 +158,7 @@ void async_run_on_cpu(CPUState *cpu, run_on_cpu_func func,
void *data)
wi->func = func;
wi->data = data;
wi->free = true;
+ wi->exclusive = false;
queue_work_on_cpu(cpu, wi);
}
@@ -230,6 +232,19 @@ void cpu_exec_end(CPUState *cpu)
qemu_mutex_unlock(&qemu_cpu_list_mutex);
}
+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;
@@ -246,7 +261,21 @@ 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);
diff --git a/include/qom/cpu.h b/include/qom/cpu.h
index 934c07a..4092dd9 100644
--- a/include/qom/cpu.h
+++ b/include/qom/cpu.h
@@ -656,6 +656,20 @@ 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 address@hidden value of the CPU to obtain.
*
--
2.7.4
- Re: [Qemu-devel] [PATCH 15/16] tcg: Make tb_flush() thread safe, (continued)
[Qemu-devel] [PATCH 16/16] cpus-common: lock-free fast path for cpu_exec_start/end, Paolo Bonzini, 2016/09/19
Re: [Qemu-devel] [PATCH 16/16] cpus-common: lock-free fast path for cpu_exec_start/end, Emilio G. Cota, 2016/09/21
Re: [Qemu-devel] [PATCH 16/16] cpus-common: lock-free fast path for cpu_exec_start/end, Paolo Bonzini, 2016/09/22
[Qemu-devel] [PATCH 14/16] cpus-common: Introduce async_safe_run_on_cpu(),
Paolo Bonzini <=
Re: [Qemu-devel] [PATCH v7 00/16] cpu-exec: Safe work in quiescent state, no-reply, 2016/09/19
Re: [Qemu-devel] [PATCH v7 00/16] cpu-exec: Safe work in quiescent state, no-reply, 2016/09/19
Re: [Qemu-devel] [PATCH v7 00/16] cpu-exec: Safe work in quiescent state, Emilio G. Cota, 2016/09/21