linux-kernel - Re: [PATCH RFC 06/26] ipc: Replace spin_unlock

lists.openwall.net		lists / announce owl-users owl-dev john-users john-dev passwdqc-users yescrypt popa3d-users / oss-security kernel-hardening musl sabotage tlsify passwords / crypt-dev xvendor / Bugtraq Full-Disclosure linux-kernel linux-netdev linux-ext4 linux-hardening linux-cve-announce PHC
Open Source and information security mailing list archives

Hash Suite: Windows password security audit tool. GUI, reports in PDF.

[<prev] [next>] [thread-next>] [day] [month] [year] [list]

Date:   Sat, 1 Jul 2017 21:23:03 +0200
From:   Manfred Spraul <manfred@...orfullife.com>
To:     "Paul E. McKenney" <paulmck@...ux.vnet.ibm.com>,
        linux-kernel@...r.kernel.org
Cc:     netfilter-devel@...r.kernel.org, netdev@...r.kernel.org,
        oleg@...hat.com, akpm@...ux-foundation.org, mingo@...hat.com,
        dave@...olabs.net, tj@...nel.org, arnd@...db.de,
        linux-arch@...r.kernel.org, will.deacon@....com,
        peterz@...radead.org, stern@...land.harvard.edu,
        parri.andrea@...il.com, torvalds@...ux-foundation.org
Subject: Re: [PATCH RFC 06/26] ipc: Replace spin_unlock_wait() with
 lock/unlock pair

On 06/30/2017 02:01 AM, Paul E. McKenney wrote:
> There is no agreed-upon definition of spin_unlock_wait()'s semantics,
> and it appears that all callers could do just as well with a lock/unlock
> pair.  This commit therefore replaces the spin_unlock_wait() call in
> exit_sem() with spin_lock() followed immediately by spin_unlock().
> This should be safe from a performance perspective because exit_sem()
> is rarely invoked in production.
>
> Signed-off-by: Paul E. McKenney <paulmck@...ux.vnet.ibm.com>
> Cc: Andrew Morton <akpm@...ux-foundation.org>
> Cc: Davidlohr Bueso <dave@...olabs.net>
> Cc: Manfred Spraul <manfred@...orfullife.com>
> Cc: Will Deacon <will.deacon@....com>
> Cc: Peter Zijlstra <peterz@...radead.org>
> Cc: Alan Stern <stern@...land.harvard.edu>
> Cc: Andrea Parri <parri.andrea@...il.com>
> Cc: Linus Torvalds <torvalds@...ux-foundation.org>
Acked-by: Manfred Spraul <manfred@...orfullife.com>
> ---
>   ipc/sem.c | 3 ++-
>   1 file changed, 2 insertions(+), 1 deletion(-)
>
> diff --git a/ipc/sem.c b/ipc/sem.c
> index 947dc2348271..e88d0749a929 100644
> --- a/ipc/sem.c
> +++ b/ipc/sem.c
> @@ -2096,7 +2096,8 @@ void exit_sem(struct task_struct *tsk)
>   			 * possibility where we exit while freeary() didn't
>   			 * finish unlocking sem_undo_list.
>   			 */
> -			spin_unlock_wait(&ulp->lock);
> +			spin_lock(&ulp->lock);
> +			spin_unlock(&ulp->lock);
>   			rcu_read_unlock();
>   			break;
>   		}