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[2003:d9:9706:6900:416d:a911:2a67:c4df]) by smtp.googlemail.com with ESMTPSA id p15sm3463397wma.40.2019.12.18.11.25.04 (version=TLS1_3 cipher=TLS_AES_128_GCM_SHA256 bits=128/128); Wed, 18 Dec 2019 11:25:05 -0800 (PST) Subject: Re: [PATCH] Revert "ipc,sem: remove uneeded sem_undo_list lock usage in exit_sem()" To: "Herton R. Krzesinski" Cc: Ioanna Alifieraki , akpm@linux-foundation.org, arnd@arndb.de, catalin.marinas@arm.com, malat@debian.org, joel@joelfernandes.org, gustavo@embeddedor.com, linux-kernel@vger.kernel.org, jay.vosburgh@canonical.com, ioanna.alifieraki@gmail.com References: <20191211191318.11860-1-ioanna-maria.alifieraki@canonical.com> <20191217211745.GT7463@unknown> From: Manfred Spraul Message-ID: <07d574be-0d97-d0f8-8f22-017abebc6b6d@colorfullife.com> Date: Wed, 18 Dec 2019 20:25:03 +0100 User-Agent: Mozilla/5.0 (X11; Linux x86_64; rv:68.0) Gecko/20100101 Thunderbird/68.2.2 MIME-Version: 1.0 In-Reply-To: <20191217211745.GT7463@unknown> Content-Type: text/plain; charset=utf-8; format=flowed Content-Transfer-Encoding: 7bit Content-Language: en-US Sender: linux-kernel-owner@vger.kernel.org Precedence: bulk List-ID: X-Mailing-List: linux-kernel@vger.kernel.org Hello together, On 12/17/19 10:17 PM, Herton R. Krzesinski wrote: > On Mon, Dec 16, 2019 at 08:04:53PM +0100, Manfred Spraul wrote: >> Hi Ioanna, >> >> On 12/11/19 8:13 PM, Ioanna Alifieraki wrote: >> >>> [1] https://bugzilla.redhat.com/show_bug.cgi?id=1694779 >>> >>> Fixes: a97955844807 ("ipc,sem: remove uneeded sem_undo_list lock usage in exit_sem()") >>> Signed-off-by: Ioanna Alifieraki >> Acked-by: Manfred Spraul > Acked-by: Herton R. Krzesinski What I forgot: I think Cc: stable@vger.kernel.org should be added: The change is obviously correct, it fixes a real issue. >>> --- >>> ipc/sem.c | 6 ++---- >>> 1 file changed, 2 insertions(+), 4 deletions(-) >>> >>> diff --git a/ipc/sem.c b/ipc/sem.c >>> index ec97a7072413..fe12ea8dd2b3 100644 >>> --- a/ipc/sem.c >>> +++ b/ipc/sem.c >>> @@ -2368,11 +2368,9 @@ void exit_sem(struct task_struct *tsk) >>> ipc_assert_locked_object(&sma->sem_perm); >>> list_del(&un->list_id); >>> - /* we are the last process using this ulp, acquiring ulp->lock >>> - * isn't required. Besides that, we are also protected against >>> - * IPC_RMID as we hold sma->sem_perm lock now >>> - */ >>> + spin_lock(&ulp->lock); >>> list_del_rcu(&un->list_proc); >>> + spin_unlock(&ulp->lock); >>> /* perform adjustments registered in un */ >>> for (i = 0; i < sma->sem_nsems; i++) { >>