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Miller" , Eric Dumazet , Jakub Kicinski , Paolo Abeni Cc: linux-bluetooth@vger.kernel.org, netdev@vger.kernel.org, stable@vger.kernel.org, linux-kernel@vger.kernel.org, Yeoreum Yun References: <20240725134741.27281-2-yskelg@gmail.com> <9dc0399a-573a-40c1-b342-a81410864cd9@I-love.SAKURA.ne.jp> Content-Language: en-US From: Yunseong Kim In-Reply-To: <9dc0399a-573a-40c1-b342-a81410864cd9@I-love.SAKURA.ne.jp> Content-Type: text/plain; charset=UTF-8 Content-Transfer-Encoding: 7bit Hi Tetsuo, > Excuse me, but I can't interpret why this patch solves the warning. > > The warning says that list_for_each_entry_rcu() { } in > ieee80211_check_combinations() is called outside of rcu_read_lock() and > rcu_read_unlock() pair, doesn't it? How does that connected to > guarding hci_dev_test_flag() and queue_delayed_work() with rcu_read_lock() > and rcu_read_unlock() pair? Unless you guard list_for_each_entry_rcu() { } > in ieee80211_check_combinations() with rcu_read_lock() and rcu_read_unlock() > pair (or annotate that appropriate locks are already held), I can't expect > that the warning will be solved... Thank you for the code review. Sorry, I apologize for attaching the wrong kernel dump. > Also, what guarantees that drain_workqueue() won't be disturbed by > queue_work(disc_work) which will be called after "timeo" delay, for you are > not explicitly cancelling scheduled "disc_work" (unlike "cmd_timer" work > and "ncmd_timer" work shown below) before calling drain_workqueue() ? > > /* Cancel these to avoid queueing non-chained pending work */ > hci_dev_set_flag(hdev, HCI_CMD_DRAIN_WORKQUEUE); > /* Wait for > * > * if (!hci_dev_test_flag(hdev, HCI_CMD_DRAIN_WORKQUEUE)) > * queue_delayed_work(&hdev->{cmd,ncmd}_timer) > * > * inside RCU section to see the flag or complete scheduling. > */ > synchronize_rcu(); > /* Explicitly cancel works in case scheduled after setting the flag. */ > cancel_delayed_work(&hdev->cmd_timer); > cancel_delayed_work(&hdev->ncmd_timer); > > /* Avoid potential lockdep warnings from the *_flush() calls by > * ensuring the workqueue is empty up front. > */ > drain_workqueue(hdev->workqueue); Please bear with me for a moment. I'll attach the correct kernel dump and resend the patch email. Warm regards, Yunseong Kim