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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 , Stuart Hayes , Laurence Oberman , Bjorn Helgaas , kexec@lists.infradead.org, David Jeffery Subject: [PATCH 5/9] driver core: do not always lock parent in shutdown Date: Fri, 21 Aug 2026 10:24:10 -0400 Message-ID: <20260821142414.150892-6-djeffery@redhat.com> In-Reply-To: <20260821142414.150892-1-djeffery@redhat.com> References: <20260821142414.150892-1-djeffery@redhat.com> MIME-Version: 1.0 X-Scanned-By: MIMEDefang 3.4.1 on 10.30.177.111 X-Mimecast-MFC-PROC-ID: 3JZqKzuAtX_jmkNW76NOL4TTVTastXgncoax7pPRF-Q_1787322299 X-Mimecast-Originator: redhat.com Content-Transfer-Encoding: 8bit content-type: text/plain; charset="US-ASCII"; x-default=true X-CRM114-Version: 20100106-BlameMichelson ( TRE 0.9.0 (BSD) ) MR-646709E3 X-CRM114-CacheID: sfid-20260821_072649_443880_4CD89820 X-CRM114-Status: GOOD ( 19.40 ) X-BeenThere: kexec@lists.infradead.org X-Mailman-Version: 2.1.34 Precedence: list List-Id: List-Unsubscribe: , List-Archive: List-Post: List-Help: List-Subscribe: , Sender: "kexec" Errors-To: kexec-bounces+kexec=archiver.kernel.org@lists.infradead.org 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 Signed-off-by: Tarun Sahu Tested-by: Laurence Oberman --- The sashiko patch analysis may complain about the parent locking and possible use of device_move. This issue cannot currently happen as devices with need_parent_lock do not use device_move. An earlier patch also adds a warning for this condition should some future code change violate the incompatibility between need_parent_lock and device_move. drivers/base/core.c | 44 ++++++++++++++++++++++++++++---------------- 1 file changed, 28 insertions(+), 16 deletions(-) diff --git a/drivers/base/core.c b/drivers/base/core.c index a94d24b30c30..cd725466c32d 100644 --- a/drivers/base/core.c +++ b/drivers/base/core.c @@ -4910,12 +4910,10 @@ int device_change_owner(struct device *dev, kuid_t kuid, kgid_t kgid) return error; } -static void shutdown_one_device(struct device *dev, struct device *parent) +static void __shutdown_one_device(struct device *dev) { - /* hold lock to avoid race with probe/release */ - if (parent) - device_lock(parent); - device_lock(dev); + if (!dev->p || dev->p->dead) + return; /* Don't allow any more runtime suspends */ pm_runtime_get_noresume(dev); @@ -4935,13 +4933,33 @@ static void shutdown_one_device(struct device *dev, struct device *parent) 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 && !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(dev); - put_device(parent); } /** @@ -4949,7 +4967,7 @@ static void shutdown_one_device(struct device *dev, struct device *parent) */ void device_shutdown(void) { - struct device *dev, *parent; + struct device *dev; wait_for_device_probe(); device_block_probing(); @@ -4966,12 +4984,6 @@ 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 - */ - parent = get_device(dev->parent); get_device(dev); /* * Make sure the device is off the kset list, in the @@ -4980,7 +4992,7 @@ void device_shutdown(void) list_del_init(&dev->kobj.entry); spin_unlock(&devices_kset->list_lock); - shutdown_one_device(dev, parent); + shutdown_one_device(dev); spin_lock(&devices_kset->list_lock); } -- 2.55.0