diff mbox

[RFC,V7,01/19] cpus: protect queued_work_* with work_mutex.

Message ID 1439220437-23957-2-git-send-email-fred.konrad@greensocs.com
State New
Headers show

Commit Message

fred.konrad@greensocs.com Aug. 10, 2015, 3:26 p.m. UTC 
From: KONRAD Frederic <fred.konrad@greensocs.com>

This protects queued_work_* used by async_run_on_cpu, run_on_cpu and
flush_queued_work with a new lock (work_mutex) to prevent multiple (concurrent)
access.

Signed-off-by: KONRAD Frederic <fred.konrad@greensocs.com>
Reviewed-by: Alex Bennée <alex.bennee@linaro.org>

Changes V1 -> V2:
  * Unlock the mutex while running the callback.
---
 cpus.c            | 11 +++++++++++
 include/qom/cpu.h |  3 +++
 qom/cpu.c         |  1 +
 3 files changed, 15 insertions(+)

Comments

Paolo Bonzini Aug. 10, 2015, 3:59 p.m. UTC | #1 
On 10/08/2015 17:26, fred.konrad@greensocs.com wrote:
>  
> +    qemu_mutex_lock(&cpu->work_mutex);
>      while ((wi = cpu->queued_work_first)) {
>          cpu->queued_work_first = wi->next;
> +        qemu_mutex_unlock(&cpu->work_mutex);
>          wi->func(wi->data);
> +        qemu_mutex_lock(&cpu->work_mutex);
>          wi->done = true;

This should be atomic_mb_set

>          if (wi->free) {
>              g_free(wi);
>          }
>      }
>      cpu->queued_work_last = NULL;

... and I'm a bit afraid of leaving the state of the list inconsistent,
so I'd move this after the cpu->queued_work_first assignment.  Otherwise
the patch looks good, I'm queuing it for 2.5.

Paolo

> +    qemu_mutex_unlock(&cpu->work_mutex);
> +
fred.konrad@greensocs.com Aug. 10, 2015, 4:04 p.m. UTC | #2 
On 10/08/2015 17:59, Paolo Bonzini wrote:
>
> On 10/08/2015 17:26, fred.konrad@greensocs.com wrote:
>>   
>> +    qemu_mutex_lock(&cpu->work_mutex);
>>       while ((wi = cpu->queued_work_first)) {
>>           cpu->queued_work_first = wi->next;
>> +        qemu_mutex_unlock(&cpu->work_mutex);
>>           wi->func(wi->data);
>> +        qemu_mutex_lock(&cpu->work_mutex);
>>           wi->done = true;
> This should be atomic_mb_set

Isn't that protected by the mutex? Or maybe it's used somewhere else?
>
>>           if (wi->free) {
>>               g_free(wi);
>>           }
>>       }
>>       cpu->queued_work_last = NULL;
> ... and I'm a bit afraid of leaving the state of the list inconsistent,
> so I'd move this after the cpu->queued_work_first assignment.  Otherwise
> the patch looks good, I'm queuing it for 2.5.
>
> Paolo
>
>> +    qemu_mutex_unlock(&cpu->work_mutex);
>> +
Paolo Bonzini Aug. 10, 2015, 4:06 p.m. UTC | #3 
On 10/08/2015 18:04, Frederic Konrad wrote:
> On 10/08/2015 17:59, Paolo Bonzini wrote:
>>
>> On 10/08/2015 17:26, fred.konrad@greensocs.com wrote:
>>>   +    qemu_mutex_lock(&cpu->work_mutex);
>>>       while ((wi = cpu->queued_work_first)) {
>>>           cpu->queued_work_first = wi->next;
>>> +        qemu_mutex_unlock(&cpu->work_mutex);
>>>           wi->func(wi->data);
>>> +        qemu_mutex_lock(&cpu->work_mutex);
>>>           wi->done = true;
>> This should be atomic_mb_set
> 
> Isn't that protected by the mutex?

This use is not protected by the mutex:

@@ -853,6 +855,7 @@ void run_on_cpu(CPUState *cpu, void (*func)(void *data), void *data)
     cpu->queued_work_last = &wi;
     wi.next = NULL;
     wi.done = false;
+    qemu_mutex_unlock(&cpu->work_mutex);
 
     qemu_cpu_kick(cpu);
     while (!wi.done) {

Paolo

 Or maybe it's used somewhere else?
>>
>>>           if (wi->free) {
>>>               g_free(wi);
>>>           }
>>>       }
>>>       cpu->queued_work_last = NULL;
>> ... and I'm a bit afraid of leaving the state of the list inconsistent,
>> so I'd move this after the cpu->queued_work_first assignment.  Otherwise
>> the patch looks good, I'm queuing it for 2.5.
>>
>> Paolo
>>
>>> +    qemu_mutex_unlock(&cpu->work_mutex);
>>> +
>
diff mbox

Patch

diff --git a/cpus.c b/cpus.c
index b00a423..eabd4b1 100644
--- a/cpus.c
+++ b/cpus.c
@@ -845,6 +845,8 @@  void run_on_cpu(CPUState *cpu, void (*func)(void *data), void *data)
     wi.func = func;
     wi.data = data;
     wi.free = false;
+
+    qemu_mutex_lock(&cpu->work_mutex);
     if (cpu->queued_work_first == NULL) {
         cpu->queued_work_first = &wi;
     } else {
@@ -853,6 +855,7 @@  void run_on_cpu(CPUState *cpu, void (*func)(void *data), void *data)
     cpu->queued_work_last = &wi;
     wi.next = NULL;
     wi.done = false;
+    qemu_mutex_unlock(&cpu->work_mutex);
 
     qemu_cpu_kick(cpu);
     while (!wi.done) {
@@ -876,6 +879,8 @@  void async_run_on_cpu(CPUState *cpu, void (*func)(void *data), void *data)
     wi->func = func;
     wi->data = data;
     wi->free = true;
+
+    qemu_mutex_lock(&cpu->work_mutex);
     if (cpu->queued_work_first == NULL) {
         cpu->queued_work_first = wi;
     } else {
@@ -884,6 +889,7 @@  void async_run_on_cpu(CPUState *cpu, void (*func)(void *data), void *data)
     cpu->queued_work_last = wi;
     wi->next = NULL;
     wi->done = false;
+    qemu_mutex_unlock(&cpu->work_mutex);
 
     qemu_cpu_kick(cpu);
 }
@@ -896,15 +902,20 @@  static void flush_queued_work(CPUState *cpu)
         return;
     }
 
+    qemu_mutex_lock(&cpu->work_mutex);
     while ((wi = cpu->queued_work_first)) {
         cpu->queued_work_first = wi->next;
+        qemu_mutex_unlock(&cpu->work_mutex);
         wi->func(wi->data);
+        qemu_mutex_lock(&cpu->work_mutex);
         wi->done = true;
         if (wi->free) {
             g_free(wi);
         }
     }
     cpu->queued_work_last = NULL;
+    qemu_mutex_unlock(&cpu->work_mutex);
+
     qemu_cond_broadcast(&qemu_work_cond);
 }
 
diff --git a/include/qom/cpu.h b/include/qom/cpu.h
index 20aabc9..efa9624 100644
--- a/include/qom/cpu.h
+++ b/include/qom/cpu.h
@@ -242,6 +242,8 @@  struct kvm_run;
  * @mem_io_pc: Host Program Counter at which the memory was accessed.
  * @mem_io_vaddr: Target virtual address at which the memory was accessed.
  * @kvm_fd: vCPU file descriptor for KVM.
+ * @work_mutex: Lock to prevent multiple access to queued_work_*.
+ * @queued_work_first: First asynchronous work pending.
  *
  * State of one CPU core or thread.
  */
@@ -262,6 +264,7 @@  struct CPUState {
     uint32_t host_tid;
     bool running;
     struct QemuCond *halt_cond;
+    QemuMutex work_mutex;
     struct qemu_work_item *queued_work_first, *queued_work_last;
     bool thread_kicked;
     bool created;
diff --git a/qom/cpu.c b/qom/cpu.c
index eb9cfec..4e12598 100644
--- a/qom/cpu.c
+++ b/qom/cpu.c
@@ -316,6 +316,7 @@  static void cpu_common_initfn(Object *obj)
     cpu->gdb_num_regs = cpu->gdb_num_g_regs = cc->gdb_num_core_regs;
     QTAILQ_INIT(&cpu->breakpoints);
     QTAILQ_INIT(&cpu->watchpoints);
+    qemu_mutex_init(&cpu->work_mutex);
 }
 
 static void cpu_common_finalize(Object *obj)