[dpdk-stable] [PATCH] lib/rcu: fix possible spurious thread unregister

[dpdk-stable] [PATCH] lib/rcu: fix possible spurious thread unregister

[Ruifeng Wang]

Thread unregister returns success while unregister not been performed.
This is due to incorrect thread registration status check.
Fix this issue by correcting bitmap check.

Fixes: 64994b56cfd7 ("rcu: add RCU library supporting QSBR mechanism")
Cc: stable@dpdk.org

Signed-off-by: Ruifeng Wang <ruifeng.wang@arm.com>
Reviewed-by: Gavin Hu <gavin.hu@arm.com>
---
 lib/librte_rcu/rte_rcu_qsbr.c | 4 ++--
 1 file changed, 2 insertions(+), 2 deletions(-)

diff --git a/lib/librte_rcu/rte_rcu_qsbr.c b/lib/librte_rcu/rte_rcu_qsbr.c
index ce7f93dd3..8c37c88cd 100644
--- a/lib/librte_rcu/rte_rcu_qsbr.c
+++ b/lib/librte_rcu/rte_rcu_qsbr.c
@@ -158,7 +158,7 @@ rte_rcu_qsbr_thread_unregister(struct rte_rcu_qsbr *v, unsigned int thread_id)
 	/* Check if the thread is already unregistered */
 	old_bmap = __atomic_load_n(__RTE_QSBR_THRID_ARRAY_ELM(v, i),
 					__ATOMIC_RELAXED);
-	if (old_bmap & ~(1UL << id))
+	if (!(old_bmap & (1UL << id)))
 		return 0;
 
 	do {
@@ -175,7 +175,7 @@ rte_rcu_qsbr_thread_unregister(struct rte_rcu_qsbr *v, unsigned int thread_id)
 		if (success)
 			__atomic_fetch_sub(&v->num_threads,
 						1, __ATOMIC_RELAXED);
-		else if (old_bmap & ~(1UL << id))
+		else if (!(old_bmap & (1UL << id)))
 			/* Someone else unregistered this thread.
 			 * Counter should not be incremented.
 			 */
-- 
2.17.1

Re: [dpdk-stable] [PATCH] lib/rcu: fix possible spurious thread unregister

[Honnappa Nagarahalli]

Thanks Ruifeng, looks good.

> -----Original Message-----
> From: Ruifeng Wang <ruifeng.wang@arm.com>
> Sent: Monday, September 9, 2019 8:52 AM
> To: Honnappa Nagarahalli <Honnappa.Nagarahalli@arm.com>
> Cc: dev@dpdk.org; Gavin Hu (Arm Technology China) <Gavin.Hu@arm.com>;
> nd <nd@arm.com>; Ruifeng Wang (Arm Technology China)
> <Ruifeng.Wang@arm.com>; stable@dpdk.org
> Subject: [PATCH] lib/rcu: fix possible spurious thread unregister
> 
> Thread unregister returns success while unregister not been performed.
> This is due to incorrect thread registration status check.
> Fix this issue by correcting bitmap check.
> 
> Fixes: 64994b56cfd7 ("rcu: add RCU library supporting QSBR mechanism")
> Cc: stable@dpdk.org
> 
> Signed-off-by: Ruifeng Wang <ruifeng.wang@arm.com>
> Reviewed-by: Gavin Hu <gavin.hu@arm.com>
> ---
>  lib/librte_rcu/rte_rcu_qsbr.c | 4 ++--
>  1 file changed, 2 insertions(+), 2 deletions(-)
> 
> diff --git a/lib/librte_rcu/rte_rcu_qsbr.c b/lib/librte_rcu/rte_rcu_qsbr.c index
> ce7f93dd3..8c37c88cd 100644
> --- a/lib/librte_rcu/rte_rcu_qsbr.c
> +++ b/lib/librte_rcu/rte_rcu_qsbr.c
> @@ -158,7 +158,7 @@ rte_rcu_qsbr_thread_unregister(struct rte_rcu_qsbr
> *v, unsigned int thread_id)
>  	/* Check if the thread is already unregistered */
>  	old_bmap = __atomic_load_n(__RTE_QSBR_THRID_ARRAY_ELM(v, i),
>  					__ATOMIC_RELAXED);
> -	if (old_bmap & ~(1UL << id))
> +	if (!(old_bmap & (1UL << id)))
>  		return 0;
> 
>  	do {
> @@ -175,7 +175,7 @@ rte_rcu_qsbr_thread_unregister(struct rte_rcu_qsbr
> *v, unsigned int thread_id)
>  		if (success)
>  			__atomic_fetch_sub(&v->num_threads,
>  						1, __ATOMIC_RELAXED);
> -		else if (old_bmap & ~(1UL << id))
> +		else if (!(old_bmap & (1UL << id)))
>  			/* Someone else unregistered this thread.
>  			 * Counter should not be incremented.
>  			 */
> --
Reviewed-by: Honnappa Nagarahalli <honnappa.nagarahalli@arm.com>

> 2.17.1

Re: [dpdk-stable] [dpdk-dev] [PATCH] lib/rcu: fix possible spurious thread unregister

[David Marchand]

On Mon, Sep 9, 2019 at 3:52 PM Ruifeng Wang <ruifeng.wang@arm.com> wrote:
>
> Thread unregister returns success while unregister not been performed.
> This is due to incorrect thread registration status check.
> Fix this issue by correcting bitmap check.
>
> Fixes: 64994b56cfd7 ("rcu: add RCU library supporting QSBR mechanism")
> Cc: stable@dpdk.org
>
> Signed-off-by: Ruifeng Wang <ruifeng.wang@arm.com>
> Reviewed-by: Gavin Hu <gavin.hu@arm.com>
> ---
>  lib/librte_rcu/rte_rcu_qsbr.c | 4 ++--
>  1 file changed, 2 insertions(+), 2 deletions(-)
>
> diff --git a/lib/librte_rcu/rte_rcu_qsbr.c b/lib/librte_rcu/rte_rcu_qsbr.c
> index ce7f93dd3..8c37c88cd 100644
> --- a/lib/librte_rcu/rte_rcu_qsbr.c
> +++ b/lib/librte_rcu/rte_rcu_qsbr.c
> @@ -158,7 +158,7 @@ rte_rcu_qsbr_thread_unregister(struct rte_rcu_qsbr *v, unsigned int thread_id)
>         /* Check if the thread is already unregistered */
>         old_bmap = __atomic_load_n(__RTE_QSBR_THRID_ARRAY_ELM(v, i),
>                                         __ATOMIC_RELAXED);
> -       if (old_bmap & ~(1UL << id))
> +       if (!(old_bmap & (1UL << id)))
>                 return 0;
>
>         do {
> @@ -175,7 +175,7 @@ rte_rcu_qsbr_thread_unregister(struct rte_rcu_qsbr *v, unsigned int thread_id)
>                 if (success)
>                         __atomic_fetch_sub(&v->num_threads,
>                                                 1, __ATOMIC_RELAXED);
> -               else if (old_bmap & ~(1UL << id))
> +               else if (!(old_bmap & (1UL << id)))
>                         /* Someone else unregistered this thread.
>                          * Counter should not be incremented.
>                          */

Reviewed-by: David Marchand <david.marchand@redhat.com>


Honnappa,

While looking at the rcu doxygen, I noted it does not describe what
return values to expect from register/unregister.
We also have typos on s/rte_rcu_thread_offline/rte_rcu_qsbr_thread_offline/g.

Could you send a patch for this?


Thanks.

--
David Marchand

Re: [dpdk-stable] [dpdk-dev] [PATCH] lib/rcu: fix possible spurious thread unregister

[David Marchand]

On Wed, Sep 25, 2019 at 10:01 AM David Marchand
<david.marchand@redhat.com> wrote:
>
> On Mon, Sep 9, 2019 at 3:52 PM Ruifeng Wang <ruifeng.wang@arm.com> wrote:
> >
> > Thread unregister returns success while unregister not been performed.
> > This is due to incorrect thread registration status check.
> > Fix this issue by correcting bitmap check.
> >
> > Fixes: 64994b56cfd7 ("rcu: add RCU library supporting QSBR mechanism")
> > Cc: stable@dpdk.org
> >
> > Signed-off-by: Ruifeng Wang <ruifeng.wang@arm.com>
> > Reviewed-by: Gavin Hu <gavin.hu@arm.com>
> Reviewed-by: Honnappa Nagarahalli <honnappa.nagarahalli@arm.com>
> Reviewed-by: David Marchand <david.marchand@redhat.com>

Applied, thanks.



--
David Marchand