mptcp_get_available_schedulers() needs to iterate over the schedulers'
list only to read the names: it doesn't modify anything there.

In this case, it is enough to hold the RCU read lock, no need to combine
this with the associated spin lock.

Fixes: 73c900aa3660 ("mptcp: add net.mptcp.available_schedulers")
Suggested-by: Paolo Abeni <pabeni@redhat.com>
Signed-off-by: Matthieu Baerts (NGI0) <matttbe@kernel.org>
---
 net/mptcp/sched.c | 2 --
 1 file changed, 2 deletions(-)

diff --git a/net/mptcp/sched.c b/net/mptcp/sched.c
index 5257bc6c8cd6e8ca674c9beccaf7b27c989da76a..6da60e35932ffd8a92ad7a8b128e5eaf09219b82 100644
--- a/net/mptcp/sched.c
+++ b/net/mptcp/sched.c
@@ -60,7 +60,6 @@ void mptcp_get_available_schedulers(char *buf, size_t maxlen)
 	size_t offs = 0;
 
 	rcu_read_lock();
-	spin_lock(&mptcp_sched_list_lock);
 	list_for_each_entry_rcu(sched, &mptcp_sched_list, list) {
 		offs += snprintf(buf + offs, maxlen - offs,
 				 "%s%s",
@@ -69,7 +68,6 @@ void mptcp_get_available_schedulers(char *buf, size_t maxlen)
 		if (WARN_ON_ONCE(offs >= maxlen))
 			break;
 	}
-	spin_unlock(&mptcp_sched_list_lock);
 	rcu_read_unlock();
 }
 

-- 
2.45.2

Hi Matt,

Thanks for this fix.

On Thu, 2024-10-17 at 12:16 +0200, Matthieu Baerts (NGI0) wrote:
> mptcp_get_available_schedulers() needs to iterate over the
> schedulers'
> list only to read the names: it doesn't modify anything there.
> 
> In this case, it is enough to hold the RCU read lock, no need to
> combine
> this with the associated spin lock.
> 
> Fixes: 73c900aa3660 ("mptcp: add net.mptcp.available_schedulers")
> Suggested-by: Paolo Abeni <pabeni@redhat.com>
> Signed-off-by: Matthieu Baerts (NGI0) <matttbe@kernel.org>

Good catch!

Reviewed-by: Geliang Tang <geliang@kernel.org>

-Geliang

> ---
>  net/mptcp/sched.c | 2 --
>  1 file changed, 2 deletions(-)
> 
> diff --git a/net/mptcp/sched.c b/net/mptcp/sched.c
> index
> 5257bc6c8cd6e8ca674c9beccaf7b27c989da76a..6da60e35932ffd8a92ad7a8b128
> e5eaf09219b82 100644
> --- a/net/mptcp/sched.c
> +++ b/net/mptcp/sched.c
> @@ -60,7 +60,6 @@ void mptcp_get_available_schedulers(char *buf,
> size_t maxlen)
>  	size_t offs = 0;
>  
>  	rcu_read_lock();
> -	spin_lock(&mptcp_sched_list_lock);
>  	list_for_each_entry_rcu(sched, &mptcp_sched_list, list) {
>  		offs += snprintf(buf + offs, maxlen - offs,
>  				 "%s%s",
> @@ -69,7 +68,6 @@ void mptcp_get_available_schedulers(char *buf,
> size_t maxlen)
>  		if (WARN_ON_ONCE(offs >= maxlen))
>  			break;
>  	}
> -	spin_unlock(&mptcp_sched_list_lock);
>  	rcu_read_unlock();
>  }
>  
>