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Mon, 02 Nov 2026 04:23:53 -0800 (PST) Received: from thinkpad.lan ([2a06:c701:4773:6f00:e7fd:cb78:efe4:a8de]) by smtp.gmail.com with ESMTPSA id 5b1f17b1804b1-4abf723b5dcsm271952215e9.14.2026.11.02.04.23.51 (version=TLS1_3 cipher=TLS_AES_256_GCM_SHA384 bits=256/256); Mon, 02 Nov 2026 04:23:53 -0800 (PST) From: Avi Weiss To: Richard Cochran Cc: netdev@vger.kernel.org, davem@davemloft.net, edumazet@kernel.org, kuba@kernel.org, pabeni@redhat.com, linux-kernel@vger.kernel.org Subject: [PATCH net] ptp: Report clock removal to poll waiters Date: Mon, 2 Nov 2026 14:23:40 +0200 Message-ID: <20261102122340.1160733-1-thnkslprpt@gmail.com> X-Mailer: git-send-email 2.53.0 X-Mailing-List: linux-kernel@vger.kernel.org List-Id: List-Post: List-Help: List-Subscribe: List-Unsubscribe: List-Owner: Precedence: list MIME-Version: 1.0 Content-Transfer-Encoding: 8bit ptp_clock_unregister() marks the clock defunct and wake timestamp waiters before posix_clock_unregister() marks it inactive. A poll waiter can consume the removal wakeup while the event queue is empty, return no events, and remain blocked until timeout after device removal. Identified while reviewing the PTP polling and removal paths. Using netdevsim's mock PTP clock in an x86_64 QEMU/KVM guest, the unpatched kernel missed 8 of 12 removal notifications, while the patched kernel reported all 12. No kernel instrumentation or forced fault injection was required. W=1, ptp_chardev.o compiled under allyesconfig and allmodconfig on net/main. Check the defunct state after registering the poll wait queue and return EPOLLERR when the clock is being removed. Fixes: d94ba80ebbea ("ptp: Added a brand new class driver for ptp clocks.") Signed-off-by: Avi Weiss --- drivers/ptp/ptp_chardev.c | 3 +++ 1 file changed, 3 insertions(+) diff --git a/drivers/ptp/ptp_chardev.c b/drivers/ptp/ptp_chardev.c index f63b45f5ee6a..01adc70ad97b 100644 --- a/drivers/ptp/ptp_chardev.c +++ b/drivers/ptp/ptp_chardev.c @@ -593,6 +593,9 @@ __poll_t ptp_poll(struct posix_clock_context *pccontext, struct file *fp, poll_wait(fp, &ptp->tsev_wq, wait); + if (READ_ONCE(ptp->defunct)) + return EPOLLERR; + return queue_cnt(queue) ? EPOLLIN : 0; } base-commit: cb284914e749388eef402938bdb3115fe1f6d337 -- 2.53.0