rcu: Call drain_call_rcu at exit

[PATCH] rcu: Call drain_call_rcu at exit

Posted by Akihiko Odaki 1 year, 3 months ago

call_rcu() callbacks may have potential memory leaks, but QEMU may
sometimes exit before draining the callbacks and leave the leaks
undetected by LeakSanitizer. For example, PCI devices register a
call_rcu() callback by calling address_space_destroy() and they will
not be freed until it gets drained. This hides memory leaks that
is going to happen when PCI devices loose references to the memory
allocations.

Call drain_call_rcu at exit to expose memory leaks by call_rcu()
callbacks deterministically.

Signed-off-by: Akihiko Odaki <akihiko.odaki@daynix.com>
---
 util/rcu.c | 1 +
 1 file changed, 1 insertion(+)

diff --git a/util/rcu.c b/util/rcu.c
index fa32c942e4bb..118a974e3438 100644
--- a/util/rcu.c
+++ b/util/rcu.c
@@ -415,6 +415,7 @@ static void rcu_init_complete(void)
     qemu_thread_create(&thread, "call_rcu", call_rcu_thread,
                        NULL, QEMU_THREAD_DETACHED);
 
+    atexit(drain_call_rcu);
     rcu_register_thread();
 }
 

---
base-commit: 31669121a01a14732f57c49400bc239cf9fd505f
change-id: 20241013-rcu-b4864052a103

Best regards,
-- 
Akihiko Odaki <akihiko.odaki@daynix.com>

Re: [PATCH] rcu: Call drain_call_rcu at exit

Posted by Akihiko Odaki 1 year ago

Hi Paolo,

Please review this patch.

Regards,
Akihiko Odaki

On 2024/10/13 16:31, Akihiko Odaki wrote:
> call_rcu() callbacks may have potential memory leaks, but QEMU may
> sometimes exit before draining the callbacks and leave the leaks
> undetected by LeakSanitizer. For example, PCI devices register a
> call_rcu() callback by calling address_space_destroy() and they will
> not be freed until it gets drained. This hides memory leaks that
> is going to happen when PCI devices loose references to the memory
> allocations.
> 
> Call drain_call_rcu at exit to expose memory leaks by call_rcu()
> callbacks deterministically.
> 
> Signed-off-by: Akihiko Odaki <akihiko.odaki@daynix.com>
> ---
>   util/rcu.c | 1 +
>   1 file changed, 1 insertion(+)
> 
> diff --git a/util/rcu.c b/util/rcu.c
> index fa32c942e4bb..118a974e3438 100644
> --- a/util/rcu.c
> +++ b/util/rcu.c
> @@ -415,6 +415,7 @@ static void rcu_init_complete(void)
>       qemu_thread_create(&thread, "call_rcu", call_rcu_thread,
>                          NULL, QEMU_THREAD_DETACHED);
>   
> +    atexit(drain_call_rcu);
>       rcu_register_thread();
>   }
>   
> 
> ---
> base-commit: 31669121a01a14732f57c49400bc239cf9fd505f
> change-id: 20241013-rcu-b4864052a103
> 
> Best regards,