Re: [Qemu-block] [PATCH v3 4/9] qcow2-threads: qcow2_co_do_compress: protect queuing by mutex

[Vladimir Sementsov-Ogievskiy]

16.01.2019 2:29, Paolo Bonzini wrote:
> On 08/01/19 18:06, Vladimir Sementsov-Ogievskiy wrote:
>> Signed-off-by: Vladimir Sementsov-Ogievskiy 
>> ---
>>   block/qcow2-threads.c | 10 +++---
>>   1 file changed, 7 insertions(+), 3 deletions(-)
>>
>> diff --git a/block/qcow2-threads.c b/block/qcow2-threads.c
>> index 20b2616529..156e0667be 100644
>> --- a/block/qcow2-threads.c
>> +++ b/block/qcow2-threads.c
>> @@ -158,15 +158,19 @@ qcow2_co_do_compress(BlockDriverState *bs, void *dest, 
>> size_t dest_size,
>>   .func = func,
>>   };
>>   
>> +qemu_co_mutex_lock(>lock);
>>   while (s->nb_compress_threads >= MAX_COMPRESS_THREADS) {
>> -qemu_co_queue_wait(>compress_wait_queue, NULL);
>> +qemu_co_queue_wait(>compress_wait_queue, >lock);
>>   }
>> -
>>   s->nb_compress_threads++;
>> +qemu_co_mutex_unlock(>lock);
>> +
>>   thread_pool_submit_co(pool, qcow2_compress_pool_func, );
>> -s->nb_compress_threads--;
>>   
>> +qemu_co_mutex_lock(>lock);
>> +s->nb_compress_threads--;
>>   qemu_co_queue_next(>compress_wait_queue);
>> +qemu_co_mutex_unlock(>lock);
>>   
>>   return arg.ret;
>>   }
>>
> 
> Reviewed-by: Paolo Bonzini 
> 
> but, some information would be nice to have in the commit message.

Could you suggest one?

Just, "To make it thread-safe."? I don't have good understanding
of moving from "AioContext lock usage" to other locks, as well as
I don't know how BlockDriverState is going to be used in parallel
threads, and how much of other code is already prepared to work
in multiple-threads environment.

I looked through your commit messages on patches which added protection
to similar places about co-queues, but didn't find detailed description.

> 
> Paolo
> 


-- 
Best regards,
Vladimir

Re: [Qemu-block] [PATCH v3 4/9] qcow2-threads: qcow2_co_do_compress: protect queuing by mutex

[Alberto Garcia]

On Tue 08 Jan 2019 06:06:50 PM CET, Vladimir Sementsov-Ogievskiy wrote:
> Signed-off-by: Vladimir Sementsov-Ogievskiy 

Reviewed-by: Alberto Garcia 

Berto

Re: [Qemu-block] [PATCH v3 4/9] qcow2-threads: qcow2_co_do_compress: protect queuing by mutex

[Paolo Bonzini]

On 08/01/19 18:06, Vladimir Sementsov-Ogievskiy wrote:
> Signed-off-by: Vladimir Sementsov-Ogievskiy 
> ---
>  block/qcow2-threads.c | 10 +++---
>  1 file changed, 7 insertions(+), 3 deletions(-)
> 
> diff --git a/block/qcow2-threads.c b/block/qcow2-threads.c
> index 20b2616529..156e0667be 100644
> --- a/block/qcow2-threads.c
> +++ b/block/qcow2-threads.c
> @@ -158,15 +158,19 @@ qcow2_co_do_compress(BlockDriverState *bs, void *dest, 
> size_t dest_size,
>  .func = func,
>  };
>  
> +qemu_co_mutex_lock(>lock);
>  while (s->nb_compress_threads >= MAX_COMPRESS_THREADS) {
> -qemu_co_queue_wait(>compress_wait_queue, NULL);
> +qemu_co_queue_wait(>compress_wait_queue, >lock);
>  }
> -
>  s->nb_compress_threads++;
> +qemu_co_mutex_unlock(>lock);
> +
>  thread_pool_submit_co(pool, qcow2_compress_pool_func, );
> -s->nb_compress_threads--;
>  
> +qemu_co_mutex_lock(>lock);
> +s->nb_compress_threads--;
>  qemu_co_queue_next(>compress_wait_queue);
> +qemu_co_mutex_unlock(>lock);
>  
>  return arg.ret;
>  }
> 

Reviewed-by: Paolo Bonzini 

but, some information would be nice to have in the commit message.

Paolo

[Qemu-block] [PATCH v3 4/9] qcow2-threads: qcow2_co_do_compress: protect queuing by mutex

[Vladimir Sementsov-Ogievskiy]

Signed-off-by: Vladimir Sementsov-Ogievskiy 
---
 block/qcow2-threads.c | 10 +++---
 1 file changed, 7 insertions(+), 3 deletions(-)

diff --git a/block/qcow2-threads.c b/block/qcow2-threads.c
index 20b2616529..156e0667be 100644
--- a/block/qcow2-threads.c
+++ b/block/qcow2-threads.c
@@ -158,15 +158,19 @@ qcow2_co_do_compress(BlockDriverState *bs, void *dest, 
size_t dest_size,
 .func = func,
 };
 
+qemu_co_mutex_lock(>lock);
 while (s->nb_compress_threads >= MAX_COMPRESS_THREADS) {
-qemu_co_queue_wait(>compress_wait_queue, NULL);
+qemu_co_queue_wait(>compress_wait_queue, >lock);
 }
-
 s->nb_compress_threads++;
+qemu_co_mutex_unlock(>lock);
+
 thread_pool_submit_co(pool, qcow2_compress_pool_func, );
-s->nb_compress_threads--;
 
+qemu_co_mutex_lock(>lock);
+s->nb_compress_threads--;
 qemu_co_queue_next(>compress_wait_queue);
+qemu_co_mutex_unlock(>lock);
 
 return arg.ret;
 }
-- 
2.18.0