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Wysocki" , Danilo Krummrich Cc: linux-kernel@vger.kernel.org, linux-pci@vger.kernel.org, linux-scsi@vger.kernel.org, Tarun Sahu , Pasha Tatashin , =?UTF-8?q?Micha=C5=82=20C=C5=82api=C5=84ski?= , Jordan Richards , Ewan Milne , John Meneghini , "Lombardi, Maurizio" , Stuart Hayes , Laurence Oberman , Bart Van Assche , Bjorn Helgaas , "Martin K . Petersen" , John Garry , kexec@lists.infradead.org, David Jeffery Subject: [PATCH 2/5] driver core: do not always lock parent in shutdown Date: Tue, 16 Jun 2026 11:22:16 -0400 Message-ID: <20260616152219.6268-3-djeffery@redhat.com> In-Reply-To: <20260616152219.6268-1-djeffery@redhat.com> References: <20260616152219.6268-1-djeffery@redhat.com> Precedence: bulk X-Mailing-List: driver-core@lists.linux.dev List-Id: List-Subscribe: List-Unsubscribe: MIME-Version: 1.0 X-Scanned-By: MIMEDefang 3.4.1 on 10.30.177.111 X-Mimecast-MFC-PROC-ID: Vwjyjw4m1vsXoW9KSwdnGxwp_uWmlcJtyj7GHJlQbTQ_1781623375 X-Mimecast-Originator: redhat.com Content-Transfer-Encoding: 8bit content-type: text/plain; charset="US-ASCII"; x-default=true Don't lock a parent device unless it is needed in device_shutdown. This is in preparation for making device shutdown asynchronous, when it will be needed to allow children of a common parent to shut down simultaneously. And only acquire a reference to the parent device if the parent is to be locked. Signed-off-by: Stuart Hayes Signed-off-by: David Jeffery Tested-by: Laurence Oberman --- drivers/base/core.c | 42 ++++++++++++++++++++++++++---------------- 1 file changed, 26 insertions(+), 16 deletions(-) diff --git a/drivers/base/core.c b/drivers/base/core.c index 74c693cd19cf..3b3d983b1747 100644 --- a/drivers/base/core.c +++ b/drivers/base/core.c @@ -4865,14 +4865,10 @@ int device_change_owner(struct device *dev, kuid_t kuid, kgid_t kgid) return error; } -static void shutdown_one_device(struct device *dev) +static void __shutdown_one_device(struct device *dev) { - struct device *parent = dev->parent; - - /* hold lock to avoid race with probe/release */ - if (parent) - device_lock(parent); - device_lock(dev); + if (dev->p->dead) + return; /* Don't allow any more runtime suspends */ pm_runtime_get_noresume(dev); @@ -4892,12 +4888,32 @@ static void shutdown_one_device(struct device *dev) dev_info(dev, "shutdown\n"); dev->driver->shutdown(dev); } +} - device_unlock(dev); - if (parent) +static void shutdown_one_device(struct device *dev) +{ + struct device *parent; + + device_lock(dev); + + /* use parent lock if needed to avoid race with probe/release */ + if (dev->bus && dev->bus->need_parent_lock && !dev->p->dead && + (parent = get_device(dev->parent))) { + /* the parent lock needs to be acquired first, so re-lock */ + device_unlock(dev); + + device_lock(parent); + device_lock(dev); + + __shutdown_one_device(dev); + device_unlock(dev); device_unlock(parent); + put_device(parent); + } else { + __shutdown_one_device(dev); + device_unlock(dev); + } - put_device(parent); put_device(dev); } @@ -4923,12 +4939,6 @@ void device_shutdown(void) dev = list_entry(devices_kset->list.prev, struct device, kobj.entry); - /* - * hold reference count of device's parent to - * prevent it from being freed because parent's - * lock is to be held - */ - get_device(dev->parent); get_device(dev); /* * Make sure the device is off the kset list, in the -- 2.54.0