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Tue, 20 Oct 2026 15:44:25 +0000 (GMT) Received: from osiris (unknown [9.111.79.24]) by smtpav04.fra02v.mail.ibm.com (Postfix) with ESMTPS; Tue, 20 Oct 2026 15:44:25 +0000 (GMT) Date: Tue, 20 Oct 2026 17:44:24 +0200 From: Heiko Carstens To: Tristan Madani Cc: Vasily Gorbik , linux-s390@vger.kernel.org, stable@vger.kernel.org, Tristan Madani , Jan Hoeppner , Alexander Gordeev Subject: Re: [PATCH v2] s390/tape: cancel delayed work on device removal Message-ID: <20261020154424.11179A48-hca@linux.ibm.com> References: <20261019225606.1864082-1-tristmd@gmail.com> X-Mailing-List: linux-s390@vger.kernel.org List-Id: List-Post: List-Help: List-Subscribe: List-Unsubscribe: List-Owner: Precedence: list MIME-Version: 1.0 Content-Type: text/plain; charset=us-ascii Content-Disposition: inline In-Reply-To: <20261019225606.1864082-1-tristmd@gmail.com> X-TM-AS-GCONF: 00 X-Proofpoint-Reinject: loops=2 maxloops=12 X-Proofpoint-GUID: q4Nsocebnq12uBN_x8eXUjFn_4IfsPlZ X-Proofpoint-ORIG-GUID: uPohOZ3M8s2GzHMkn8y74xzP51OgZGLS X-Proofpoint-Spam-Info: AW1haW4tMjYxMDIwMDA2MiBTYWx0ZWRfX10mq3McSe6Rm ys5zq3MVjYiekdU60yh7axc+GejGgn2QpLh6gQswp3qNzGrrbPSwB02xQzO/M2MjgZdCJ+GIr2Y yrdspkXPgS3Hic0WaCNelBjvN6KRNNE= X-Proofpoint-Spam-Details-Enc: AW1haW4tMjYxMDIwMDA2MiBTYWx0ZWRfX1sDFhXajdop9 lbK8ehdpCKTxdhdYCbnwdU841DBhtqcqArB7mmrJJuuLrInJ/q8UsTr8Cf881ouEATbPrVg6oBQ KESi0gLO5c3LQn+csHJZ180Mmeq/BkphimeY6JYgNYmR+PcuP9PRtg494JY9/RdZiqKhQnnqh6I 97A3OytaD2PTJBS/rTXzZkcHnKXKIxd1S3tqgK0jwVQTmL8P+NL+F97gQ6wXS4ZAwSQ7nUslehO PJlUFP9apnkdXTbZ1bKYLn+FEwcDV3cNAozr+0Fh1Oe5PYHopbQSoLqJ3E5GGpYq33jdHg2BoiZ DMY/BFQzhRpAH4NbUX5nE0n9yNlSP415Lzb807Vg53adg2+AoTTL4dKE9OsNtRM0fZqgh8Z+Zog yyRkoOboM9qkSildApy/wvGyR3exrCIe5N+h6DNU/hzxtT0mkGshJCXv96/8zu+weNcVT/l5aTj oJNMfxrpqA/F7ryzceg== X-Authority-Analysis: v=2.4 cv=Gb2CDgXL c=1 sm=1 tr=0 ts=6ad78c5f cx=c_pps a=GFwsV6G8L6GxiO2Y/PsHdQ==:117 a=GFwsV6G8L6GxiO2Y/PsHdQ==:17 a=kj9zAlcOel0A:10 a=660iZSQnnn4A:10 a=VkNPw1HP01LnGYTKEx00:22 a=RnoormkPH1_aCDwRdu11:22 a=uAbxVGIbfxUO_5tXvNgY:22 a=J_-Nd1mkAAAA:8 a=VwQbUJbxAAAA:8 a=lsLW7AkFJFRMs5hC4yMA:9 a=CjuIK1q_8ugA:10 a=n8ForQn92ZFaZtFqRdMw:22 X-Proofpoint-Virus-Version: vendor=baseguard engine=ICAP:2.0.293,Aquarius:18.0.1176,Hydra:6.1.134,FMLib:17.12.100.49 definitions=2026-10-20_02,2026-10-19_02,2025-10-01_01 X-Proofpoint-Spam-Details: rule=outbound_notspam policy=outbound score=0 suspectscore=0 adultscore=0 malwarescore=0 spamscore=0 phishscore=0 clxscore=1011 bulkscore=0 impostorscore=0 lowpriorityscore=0 priorityscore=1501 classifier=typeunknown authscore=0 authtc= authcc= route=outbound adjust=0 reason=mlx scancount=1 engine=8.22.0-2610190000 definitions=main-2610200062 Jan, this is for you, I would guess. [full quote below] On Mon, Oct 19, 2026 at 10:56:06PM +0000, Tristan Madani wrote: > From: Tristan Madani > > tape_generic_remove() drops the device reference without cancelling > the pending delayed work tape_dnr. If tape_delayed_next_request() is > still scheduled or running when the struct is freed on the final > reference drop, the work function dereferences freed memory. > > The cancel cannot go in tape_put_device() because that function is > called from atomic context (under get_ccwdev_lock with interrupts > disabled) and from within the work function itself, both of which > would deadlock or sleep in atomic context with cancel_delayed_work_sync(). > > Add cancel_delayed_work_sync() in tape_generic_remove() after > dev_set_drvdata() clears the device pointer and before dropping the > final reference. At this point the spinlock is not held and the device > is no longer reachable for new operations. > > Fixes: 4111796d89b8c ("[PATCH] s390: channel tape fixes") > Cc: stable@vger.kernel.org > Signed-off-by: Tristan Madani > --- > Changes in v2: > - Moved cancel from tape_put_device() to tape_generic_remove(). > tape_put_device() is called from atomic context (under spinlock with > IRQs disabled) and from within tape_delayed_next_request() itself, > so cancel_delayed_work_sync() there would deadlock or sleep in atomic. > tape_generic_remove() runs in process context with no locks held. > drivers/s390/char/tape_core.c | 1 + > 1 file changed, 1 insertion(+) > > diff --git a/drivers/s390/char/tape_core.c b/drivers/s390/char/tape_core.c > index bd8e3deb11993..cb5db2cabd21a 100644 > --- a/drivers/s390/char/tape_core.c > +++ b/drivers/s390/char/tape_core.c > @@ -662,6 +662,7 @@ tape_generic_remove(struct ccw_device *cdev) > if (device) { > sysfs_remove_group(&cdev->dev.kobj, &tape_attr_group); > dev_set_drvdata(&cdev->dev, NULL); > + cancel_delayed_work_sync(&device->tape_dnr); > tape_put_device(device); > } > } > -- > 2.47.3 >