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[46.135.95.94]) by smtp.gmail.com with ESMTPSA id 4fb4d7f45d1cf-5dcf9f6fa69sm1121849a12.73.2025.02.06.08.44.43 (version=TLS1_3 cipher=TLS_AES_256_GCM_SHA384 bits=256/256); Thu, 06 Feb 2025 08:44:45 -0800 (PST) From: Mateusz Guzik To: ebiederm@xmission.com, oleg@redhat.com Cc: brauner@kernel.org, akpm@linux-foundation.org, Liam.Howlett@oracle.com, linux-mm@kvack.org, linux-kernel@vger.kernel.org, Mateusz Guzik Subject: [PATCH v6 3/5] pid: sprinkle tasklist_lock asserts Date: Thu, 6 Feb 2025 17:44:12 +0100 Message-ID: <20250206164415.450051-4-mjguzik@gmail.com> X-Mailer: git-send-email 2.43.0 In-Reply-To: <20250206164415.450051-1-mjguzik@gmail.com> References: <20250206164415.450051-1-mjguzik@gmail.com> Precedence: bulk X-Mailing-List: linux-kernel@vger.kernel.org List-Id: List-Subscribe: List-Unsubscribe: MIME-Version: 1.0 Content-Transfer-Encoding: quoted-printable Content-Type: text/plain; charset="utf-8" They cost nothing on production kernels and document the requirement of holding the tasklist_lock lock in respective routines. Reviewed-by: Oleg Nesterov Signed-off-by: Mateusz Guzik --- kernel/pid.c | 15 ++++++++++++--- 1 file changed, 12 insertions(+), 3 deletions(-) diff --git a/kernel/pid.c b/kernel/pid.c index 924084713be8..2ae872f689a7 100644 --- a/kernel/pid.c +++ b/kernel/pid.c @@ -339,17 +339,23 @@ static struct pid **task_pid_ptr(struct task_struct *= task, enum pid_type type) */ void attach_pid(struct task_struct *task, enum pid_type type) { - struct pid *pid =3D *task_pid_ptr(task, type); + struct pid *pid; + + lockdep_assert_held_write(&tasklist_lock); + + pid =3D *task_pid_ptr(task, type); hlist_add_head_rcu(&task->pid_links[type], &pid->tasks[type]); } =20 static void __change_pid(struct task_struct *task, enum pid_type type, struct pid *new) { - struct pid **pid_ptr =3D task_pid_ptr(task, type); - struct pid *pid; + struct pid **pid_ptr, *pid; int tmp; =20 + lockdep_assert_held_write(&tasklist_lock); + + pid_ptr =3D task_pid_ptr(task, type); pid =3D *pid_ptr; =20 hlist_del_rcu(&task->pid_links[type]); @@ -386,6 +392,8 @@ void exchange_tids(struct task_struct *left, struct tas= k_struct *right) struct hlist_head *head1 =3D &pid1->tasks[PIDTYPE_PID]; struct hlist_head *head2 =3D &pid2->tasks[PIDTYPE_PID]; =20 + lockdep_assert_held_write(&tasklist_lock); + /* Swap the single entry tid lists */ hlists_swap_heads_rcu(head1, head2); =20 @@ -403,6 +411,7 @@ void transfer_pid(struct task_struct *old, struct task_= struct *new, enum pid_type type) { WARN_ON_ONCE(type =3D=3D PIDTYPE_PID); + lockdep_assert_held_write(&tasklist_lock); hlist_replace_rcu(&old->pid_links[type], &new->pid_links[type]); } =20 --=20 2.43.0