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Fri, 12 Sep 2025 14:48:28 +0000 (GMT) Message-ID: <5d94639d3db0827602e530639d699026ec092743.camel@linux.ibm.com> Subject: Re: [PATCH 2/2] PCI: Add lockdep assertion in pci_stop_and_remove_bus_device() From: Gerd Bayer To: Niklas Schnelle , Bjorn Helgaas , Lukas Wunner Cc: Keith Busch , Matthew Rosato , Benjamin Block , Halil Pasic , Farhan Ali , Julian Ruess , Heiko Carstens , Vasily Gorbik , Alexander Gordeev , linux-pci@vger.kernel.org, linux-kernel@vger.kernel.org Date: Fri, 12 Sep 2025 16:48:28 +0200 In-Reply-To: <20250826-pci_fix_sriov_disable-v1-2-2d0bc938f2a3@linux.ibm.com> References: <20250826-pci_fix_sriov_disable-v1-0-2d0bc938f2a3@linux.ibm.com> <20250826-pci_fix_sriov_disable-v1-2-2d0bc938f2a3@linux.ibm.com> Content-Type: text/plain; charset="UTF-8" Content-Transfer-Encoding: quoted-printable User-Agent: Evolution 3.56.2 (3.56.2-2.fc42) Precedence: bulk X-Mailing-List: linux-pci@vger.kernel.org List-Id: List-Subscribe: List-Unsubscribe: MIME-Version: 1.0 X-TM-AS-GCONF: 00 X-Proofpoint-GUID: Yl01E8MMDRSN5r8Mq0Xhx2pKKloWE5Hr X-Proofpoint-ORIG-GUID: Yl01E8MMDRSN5r8Mq0Xhx2pKKloWE5Hr X-Authority-Analysis: v=2.4 cv=J52q7BnS c=1 sm=1 tr=0 ts=68c432c2 cx=c_pps a=bLidbwmWQ0KltjZqbj+ezA==:117 a=bLidbwmWQ0KltjZqbj+ezA==:17 a=IkcTkHD0fZMA:10 a=yJojWOMRYYMA:10 a=VnNF1IyMAAAA:8 a=F53kh5m_LVtqdGsIIDMA:9 a=QEXdDO2ut3YA:10 X-Proofpoint-Spam-Details-Enc: AW1haW4tMjUwOTA2MDAyNSBTYWx0ZWRfX7Lsj9q8l41LL 6jzB0d79hf7nRfdQBB8jxhVKE8mB8kMFH743SFIvNxQNtCxUm3vUmdVEGTwKobKlo4o2GiKl+HZ QtZnpkgnTF2AU3sw44RBR8hfkvRcz6XmmzRfbRl5zR2bQra1X6oBnB4SXvs8p6Nuz92ZmagH0kb RuZVeKZpqzt7N+djN6cEsOXFDWWTL12JltTEoqdquvyS8doYJ9HhNH+iOek1gamniFDwsU0Ll+g sdnvJQvRNGKvXXW6X+ThaGS6AhlPJcpivw1jRjuaZEkQ3TrVQnnxdi1qB/zs6MgxdYHCWndXfic UIGBWdOVU4mcbKg8B+Kex1oaMnQsmgsqvmfD1lbkYaOElp0ypCuqabhBe7bz6QLHe5lZVOsFo8I Ly3p56u8 X-Proofpoint-Virus-Version: vendor=baseguard engine=ICAP:2.0.293,Aquarius:18.0.1117,Hydra:6.1.9,FMLib:17.12.80.40 definitions=2025-09-12_05,2025-09-11_02,2025-03-28_01 X-Proofpoint-Spam-Details: rule=outbound_notspam policy=outbound score=0 impostorscore=0 clxscore=1011 suspectscore=0 spamscore=0 phishscore=0 bulkscore=0 adultscore=0 malwarescore=0 priorityscore=1501 classifier=typeunknown authscore=0 authtc= authcc= route=outbound adjust=0 reason=mlx scancount=1 engine=8.19.0-2507300000 definitions=main-2509060025 On Tue, 2025-08-26 at 10:52 +0200, Niklas Schnelle wrote: > Removing a PCI devices requires holding pci_rescan_remove_lock. Prompted > by this being missed in sriov_disable() and going unnoticed since its > inception add a lockdep assert so this doesn't get missed again in the > future. >=20 > Reviewed-by: Benjamin Block > Signed-off-by: Niklas Schnelle > --- > drivers/pci/pci.h | 2 ++ > drivers/pci/probe.c | 2 +- > drivers/pci/remove.c | 1 + > 3 files changed, 4 insertions(+), 1 deletion(-) >=20 > diff --git a/drivers/pci/pci.h b/drivers/pci/pci.h > index 34f65d69662e9f61f0c489ec58de2ce17d21c0c6..1ad2e3ab147f3b2c42b3257e4= f366fc5e424ede3 100644 > --- a/drivers/pci/pci.h > +++ b/drivers/pci/pci.h > @@ -84,6 +84,8 @@ struct pcie_tlp_log; > extern const unsigned char pcie_link_speed[]; > extern bool pci_early_dump; > =20 > +extern struct mutex pci_rescan_remove_lock; > + > bool pcie_cap_has_lnkctl(const struct pci_dev *dev); > bool pcie_cap_has_lnkctl2(const struct pci_dev *dev); > bool pcie_cap_has_rtctl(const struct pci_dev *dev); > diff --git a/drivers/pci/probe.c b/drivers/pci/probe.c > index f41128f91ca76ab014ad669ae84a53032c7c6b6b..2b35bb39ab0366bbf86b43e72= 1811575b9fbcefb 100644 > --- a/drivers/pci/probe.c > +++ b/drivers/pci/probe.c > @@ -3469,7 +3469,7 @@ EXPORT_SYMBOL_GPL(pci_rescan_bus); > * pci_rescan_bus(), pci_rescan_bus_bridge_resize() and PCI device remov= al > * routines should always be executed under this mutex. > */ > -static DEFINE_MUTEX(pci_rescan_remove_lock); > +DEFINE_MUTEX(pci_rescan_remove_lock); > =20 > void pci_lock_rescan_remove(void) > { > diff --git a/drivers/pci/remove.c b/drivers/pci/remove.c > index 445afdfa6498edc88f1ef89df279af1419025495..0b9a609392cecba36a818bc49= 6a0af64061c259a 100644 > --- a/drivers/pci/remove.c > +++ b/drivers/pci/remove.c > @@ -138,6 +138,7 @@ static void pci_remove_bus_device(struct pci_dev *dev= ) > */ > void pci_stop_and_remove_bus_device(struct pci_dev *dev) > { > + lockdep_assert_held(&pci_rescan_remove_lock); > pci_stop_bus_device(dev); > pci_remove_bus_device(dev); > } I'm totally in favor of adding this lockdep assertion, even if this means that the mutex pci_rescan_remove_lock needs to be externalized from drivers/pci/probe.c. However, I was surprised that you didn't add the assertion to the _locked() variant until I realized that here the naming of _locked vs. not _locked variants of pci_stop_and_remove_bus_device() is just the opposite to the naming in driver/pci/pci.c: There _locked implies that the necessary lock is already held on routine entry. But this change in semantics was already introduced with commit 9d16947b7583 ("PCI: Add global pci_lock_rescan_remove()"). Looks like aligning the naming to the convention in driver/pci/pci.c would touch quite a bit of code - but so does the introduction of this lockdep assertion... Sigh, Gerd