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Mon, 17 Feb 2025 16:51:17 -0800 (PST) From: Wei Yang To: paulmck@kernel.org, frederic@kernel.org, neeraj.upadhyay@kernel.org Cc: rcu@vger.kernel.org, linux-doc@vger.kernel.org, Wei Yang , Boqun Feng , Alan Huang Subject: [Patch v2] doc/RCU/listRCU: refine example code for eliminating stale data Date: Tue, 18 Feb 2025 00:50:47 +0000 Message-Id: <20250218005047.27258-1-richard.weiyang@gmail.com> X-Mailer: git-send-email 2.11.0 Precedence: bulk X-Mailing-List: rcu@vger.kernel.org List-Id: List-Subscribe: List-Unsubscribe: This patch adjust the example code with following two purpose: * reduce the confusion on not releasing e->lock * emphasize e is valid and not stale with e->lock held Signed-off-by: Wei Yang CC: Boqun Feng CC: Alan Huang Reviewed-by: Alan Huang --- v2: * add the missing parameter *key * make function return struct audit_entry --- Documentation/RCU/listRCU.rst | 10 ++++++---- 1 file changed, 6 insertions(+), 4 deletions(-) diff --git a/Documentation/RCU/listRCU.rst b/Documentation/RCU/listRCU.rst index ed5c9d8c9afe..d8bb98623c12 100644 --- a/Documentation/RCU/listRCU.rst +++ b/Documentation/RCU/listRCU.rst @@ -334,7 +334,7 @@ If the system-call audit module were to ever need to reject stale data, one way to accomplish this would be to add a ``deleted`` flag and a ``lock`` spinlock to the ``audit_entry`` structure, and modify audit_filter_task() as follows:: - static enum audit_state audit_filter_task(struct task_struct *tsk) + static struct audit_entry *audit_filter_task(struct task_struct *tsk, char **key) { struct audit_entry *e; enum audit_state state; @@ -346,16 +346,18 @@ to accomplish this would be to add a ``deleted`` flag and a ``lock`` spinlock to if (e->deleted) { spin_unlock(&e->lock); rcu_read_unlock(); - return AUDIT_BUILD_CONTEXT; + return NULL; } rcu_read_unlock(); if (state == AUDIT_STATE_RECORD) *key = kstrdup(e->rule.filterkey, GFP_ATOMIC); - return state; + /* As long as e->lock is held, e is valid and + * its value is not stale */ + return e; } } rcu_read_unlock(); - return AUDIT_BUILD_CONTEXT; + return NULL; } The ``audit_del_rule()`` function would need to set the ``deleted`` flag under the