* [PATCH linux-next] PCI: Fix the order in unregister path @ 2021-08-25 8:34 Yajun Deng 2021-08-25 13:55 ` Rob Herring 2021-08-26 3:57 ` yajun.deng 0 siblings, 2 replies; 7+ messages in thread From: Yajun Deng @ 2021-08-25 8:34 UTC (permalink / raw) To: bhelgaas, arnd, robh, lorenzo.pieralisi Cc: linux-pci, linux-kernel, Yajun Deng device_del() should be called first and then called put_device() in unregister path, becase if that the final reference count, the device will be cleaned up via device_release() above. So use device_unregister() instead. Fixes: 9885440b16b8 (PCI: Fix pci_host_bridge struct device release/free handling) Signed-off-by: Yajun Deng <yajun.deng@linux.dev> --- drivers/pci/probe.c | 4 +--- 1 file changed, 1 insertion(+), 3 deletions(-) diff --git a/drivers/pci/probe.c b/drivers/pci/probe.c index 0ec5c792c27d..abd481a15a17 100644 --- a/drivers/pci/probe.c +++ b/drivers/pci/probe.c @@ -994,9 +994,7 @@ static int pci_register_host_bridge(struct pci_host_bridge *bridge) return 0; unregister: - put_device(&bridge->dev); - device_del(&bridge->dev); - + device_unregister(&bridge->dev); free: kfree(bus); return err; -- 2.32.0 ^ permalink raw reply related [flat|nested] 7+ messages in thread
* Re: [PATCH linux-next] PCI: Fix the order in unregister path 2021-08-25 8:34 [PATCH linux-next] PCI: Fix the order in unregister path Yajun Deng @ 2021-08-25 13:55 ` Rob Herring 2021-08-26 3:57 ` yajun.deng 1 sibling, 0 replies; 7+ messages in thread From: Rob Herring @ 2021-08-25 13:55 UTC (permalink / raw) To: Yajun Deng Cc: Bjorn Helgaas, Arnd Bergmann, Lorenzo Pieralisi, PCI, linux-kernel On Wed, Aug 25, 2021 at 3:34 AM Yajun Deng <yajun.deng@linux.dev> wrote: > > device_del() should be called first and then called put_device() in > unregister path, becase if that the final reference count, the device > will be cleaned up via device_release() above. So use device_unregister() > instead. > > Fixes: 9885440b16b8 (PCI: Fix pci_host_bridge struct device release/free handling) > Signed-off-by: Yajun Deng <yajun.deng@linux.dev> > --- > drivers/pci/probe.c | 4 +--- > 1 file changed, 1 insertion(+), 3 deletions(-) NAK. The current code is correct. Go read the comments for device_add/device_del. > diff --git a/drivers/pci/probe.c b/drivers/pci/probe.c > index 0ec5c792c27d..abd481a15a17 100644 > --- a/drivers/pci/probe.c > +++ b/drivers/pci/probe.c > @@ -994,9 +994,7 @@ static int pci_register_host_bridge(struct pci_host_bridge *bridge) > return 0; > > unregister: We get here if device_register() failed. Calling device_unregister() in that case is never right. > - put_device(&bridge->dev); This is for the get_device() we do above, not the get the driver core does. > - device_del(&bridge->dev); This undoes the device_add() we do following the comment: "NOTE: this should be called manually _iff_ device_add() was also called manually." > - > + device_unregister(&bridge->dev); > free: > kfree(bus); > return err; > -- > 2.32.0 > ^ permalink raw reply [flat|nested] 7+ messages in thread
* Re: [PATCH linux-next] PCI: Fix the order in unregister path 2021-08-25 8:34 [PATCH linux-next] PCI: Fix the order in unregister path Yajun Deng 2021-08-25 13:55 ` Rob Herring @ 2021-08-26 3:57 ` yajun.deng 2021-08-26 12:01 ` Rob Herring 2021-08-27 2:39 ` yajun.deng 1 sibling, 2 replies; 7+ messages in thread From: yajun.deng @ 2021-08-26 3:57 UTC (permalink / raw) To: Rob Herring Cc: Bjorn Helgaas, Arnd Bergmann, Lorenzo Pieralisi, PCI, linux-kernel August 25, 2021 9:55 PM, "Rob Herring" <robh@kernel.org> wrote: > On Wed, Aug 25, 2021 at 3:34 AM Yajun Deng <yajun.deng@linux.dev> wrote: > >> device_del() should be called first and then called put_device() in >> unregister path, becase if that the final reference count, the device >> will be cleaned up via device_release() above. So use device_unregister() >> instead. >> >> Fixes: 9885440b16b8 (PCI: Fix pci_host_bridge struct device release/free handling) >> Signed-off-by: Yajun Deng <yajun.deng@linux.dev> >> --- >> drivers/pci/probe.c | 4 +--- >> 1 file changed, 1 insertion(+), 3 deletions(-) > > NAK. > > The current code is correct. Go read the comments for device_add/device_del. But the device_unregister() is only contains device_del() and put_device(). It just put device_del() before put_device(). > >> diff --git a/drivers/pci/probe.c b/drivers/pci/probe.c >> index 0ec5c792c27d..abd481a15a17 100644 >> --- a/drivers/pci/probe.c >> +++ b/drivers/pci/probe.c >> @@ -994,9 +994,7 @@ static int pci_register_host_bridge(struct pci_host_bridge *bridge) >> return 0; >> >> unregister: > > We get here if device_register() failed. Calling device_unregister() > in that case is never right. > >> - put_device(&bridge->dev); > > This is for the get_device() we do above, not the get the driver core does. > >> - device_del(&bridge->dev); > > This undoes the device_add() we do following the comment: "NOTE: this > should be called manually _iff_ device_add() was also called > manually." > >> - >> + device_unregister(&bridge->dev); >> free: >> kfree(bus); >> return err; >> -- >> 2.32.0 ^ permalink raw reply [flat|nested] 7+ messages in thread
* Re: [PATCH linux-next] PCI: Fix the order in unregister path 2021-08-26 3:57 ` yajun.deng @ 2021-08-26 12:01 ` Rob Herring 2021-08-27 2:39 ` yajun.deng 1 sibling, 0 replies; 7+ messages in thread From: Rob Herring @ 2021-08-26 12:01 UTC (permalink / raw) To: Yajun Deng Cc: Bjorn Helgaas, Arnd Bergmann, Lorenzo Pieralisi, PCI, linux-kernel On Wed, Aug 25, 2021 at 10:57 PM <yajun.deng@linux.dev> wrote: > > August 25, 2021 9:55 PM, "Rob Herring" <robh@kernel.org> wrote: > > > On Wed, Aug 25, 2021 at 3:34 AM Yajun Deng <yajun.deng@linux.dev> wrote: > > > >> device_del() should be called first and then called put_device() in > >> unregister path, becase if that the final reference count, the device > >> will be cleaned up via device_release() above. So use device_unregister() > >> instead. > >> > >> Fixes: 9885440b16b8 (PCI: Fix pci_host_bridge struct device release/free handling) > >> Signed-off-by: Yajun Deng <yajun.deng@linux.dev> > >> --- > >> drivers/pci/probe.c | 4 +--- > >> 1 file changed, 1 insertion(+), 3 deletions(-) > > > > NAK. > > > > The current code is correct. Go read the comments for device_add/device_del. > > But the device_unregister() is only contains device_del() and put_device(). It just put > device_del() before put_device(). And that is the wrong order as we want to undo what the code above did. The put_device here is for the get_device we did. The put_device in device_unregister is for the get_device that device_register did (on success only). Logically, it is wrong too to call unregister if register failed. That would be like doing this: p = malloc(1); if (!p) free(p); Rob ^ permalink raw reply [flat|nested] 7+ messages in thread
* Re: [PATCH linux-next] PCI: Fix the order in unregister path 2021-08-26 3:57 ` yajun.deng 2021-08-26 12:01 ` Rob Herring @ 2021-08-27 2:39 ` yajun.deng 2021-08-30 14:55 ` Rob Herring 2021-08-31 2:41 ` yajun.deng 1 sibling, 2 replies; 7+ messages in thread From: yajun.deng @ 2021-08-27 2:39 UTC (permalink / raw) To: Rob Herring Cc: Bjorn Helgaas, Arnd Bergmann, Lorenzo Pieralisi, PCI, linux-kernel August 26, 2021 8:01 PM, "Rob Herring" <robh@kernel.org> wrote: > On Wed, Aug 25, 2021 at 10:57 PM <yajun.deng@linux.dev> wrote: > >> August 25, 2021 9:55 PM, "Rob Herring" <robh@kernel.org> wrote: >> >> On Wed, Aug 25, 2021 at 3:34 AM Yajun Deng <yajun.deng@linux.dev> wrote: >> >> device_del() should be called first and then called put_device() in >> unregister path, becase if that the final reference count, the device >> will be cleaned up via device_release() above. So use device_unregister() >> instead. >> >> Fixes: 9885440b16b8 (PCI: Fix pci_host_bridge struct device release/free handling) >> Signed-off-by: Yajun Deng <yajun.deng@linux.dev> >> --- >> drivers/pci/probe.c | 4 +--- >> 1 file changed, 1 insertion(+), 3 deletions(-) >> >> NAK. >> >> The current code is correct. Go read the comments for device_add/device_del. >> >> But the device_unregister() is only contains device_del() and put_device(). It just put >> device_del() before put_device(). > > And that is the wrong order as we want to undo what the code above > did. The put_device here is for the get_device we did. The put_device > in device_unregister is for the get_device that device_register did > (on success only). > > Logically, it is wrong too to call unregister if register failed. That > would be like doing this: > > p = malloc(1); > if (!p) > free(p); > This is the raw code: err = device_register(&bus->dev); if (err) goto unregister; unregister: put_device(&bridge->dev); device_del(&bridge->dev); This is my code: err = device_register(&bus->dev); if (err) goto unregister; unregister: device_unregister(&bridge->dev); The parameter in device_register() is bus->dev, but the parameter in device_unregister() is bridge->dev.The are different. The bridge->dev is already success before called device_register().So it wouldn't be happen like your code. > Rob ^ permalink raw reply [flat|nested] 7+ messages in thread
* Re: [PATCH linux-next] PCI: Fix the order in unregister path 2021-08-27 2:39 ` yajun.deng @ 2021-08-30 14:55 ` Rob Herring 2021-08-31 2:41 ` yajun.deng 1 sibling, 0 replies; 7+ messages in thread From: Rob Herring @ 2021-08-30 14:55 UTC (permalink / raw) To: Yajun Deng Cc: Bjorn Helgaas, Arnd Bergmann, Lorenzo Pieralisi, PCI, linux-kernel On Thu, Aug 26, 2021 at 9:39 PM <yajun.deng@linux.dev> wrote: > > August 26, 2021 8:01 PM, "Rob Herring" <robh@kernel.org> wrote: > > > On Wed, Aug 25, 2021 at 10:57 PM <yajun.deng@linux.dev> wrote: > > > >> August 25, 2021 9:55 PM, "Rob Herring" <robh@kernel.org> wrote: > >> > >> On Wed, Aug 25, 2021 at 3:34 AM Yajun Deng <yajun.deng@linux.dev> wrote: > >> > >> device_del() should be called first and then called put_device() in > >> unregister path, becase if that the final reference count, the device > >> will be cleaned up via device_release() above. So use device_unregister() > >> instead. > >> > >> Fixes: 9885440b16b8 (PCI: Fix pci_host_bridge struct device release/free handling) > >> Signed-off-by: Yajun Deng <yajun.deng@linux.dev> > >> --- > >> drivers/pci/probe.c | 4 +--- > >> 1 file changed, 1 insertion(+), 3 deletions(-) > >> > >> NAK. > >> > >> The current code is correct. Go read the comments for device_add/device_del. > >> > >> But the device_unregister() is only contains device_del() and put_device(). It just put > >> device_del() before put_device(). > > > > And that is the wrong order as we want to undo what the code above > > did. The put_device here is for the get_device we did. The put_device > > in device_unregister is for the get_device that device_register did > > (on success only). > > > > Logically, it is wrong too to call unregister if register failed. That > > would be like doing this: You are right that the register and unregister are different devices. However, your change is still wrong. The device_register is actually irrelevant. > > > > p = malloc(1); > > if (!p) > > free(p); > > > This is the raw code: > err = device_register(&bus->dev); > if (err) > goto unregister; > unregister: > put_device(&bridge->dev); > device_del(&bridge->dev); The pertinent parts are this: err = device_add(&bridge->dev); // which calls get_device() itself, so there's the first ref if (err) { put_device(&bridge->dev); goto free; } bus->bridge = get_device(&bridge->dev); // This is the 2nd ref which the PCI core holds ... unregister: put_device(&bridge->dev); // This is the put for the get_device just above here. device_del(&bridge->dev); // Then this does the 2nd put. The get_device and put_device are paired, and the device_add and device_del are paired. As I said earlier, go read the kerneldoc for device_add. For your convenience, here's the important part: device_add: * Rule of thumb is: if device_add() succeeds, you should call * device_del() when you want to get rid of it. If device_add() has * *not* succeeded, use *only* put_device() to drop the reference * count. device_del: * NOTE: this should be called manually _iff_ device_add() was * also called manually. Rob ^ permalink raw reply [flat|nested] 7+ messages in thread
* Re: [PATCH linux-next] PCI: Fix the order in unregister path 2021-08-27 2:39 ` yajun.deng 2021-08-30 14:55 ` Rob Herring @ 2021-08-31 2:41 ` yajun.deng 1 sibling, 0 replies; 7+ messages in thread From: yajun.deng @ 2021-08-31 2:41 UTC (permalink / raw) To: Rob Herring Cc: Bjorn Helgaas, Arnd Bergmann, Lorenzo Pieralisi, PCI, linux-kernel August 30, 2021 10:55 PM, "Rob Herring" <robh@kernel.org> wrote: > On Thu, Aug 26, 2021 at 9:39 PM <yajun.deng@linux.dev> wrote: > >> August 26, 2021 8:01 PM, "Rob Herring" <robh@kernel.org> wrote: >> >> On Wed, Aug 25, 2021 at 10:57 PM <yajun.deng@linux.dev> wrote: >> >> August 25, 2021 9:55 PM, "Rob Herring" <robh@kernel.org> wrote: >> >> On Wed, Aug 25, 2021 at 3:34 AM Yajun Deng <yajun.deng@linux.dev> wrote: >> >> device_del() should be called first and then called put_device() in >> unregister path, becase if that the final reference count, the device >> will be cleaned up via device_release() above. So use device_unregister() >> instead. >> >> Fixes: 9885440b16b8 (PCI: Fix pci_host_bridge struct device release/free handling) >> Signed-off-by: Yajun Deng <yajun.deng@linux.dev> >> --- >> drivers/pci/probe.c | 4 +--- >> 1 file changed, 1 insertion(+), 3 deletions(-) >> >> NAK. >> >> The current code is correct. Go read the comments for device_add/device_del. >> >> But the device_unregister() is only contains device_del() and put_device(). It just put >> device_del() before put_device(). >> >> And that is the wrong order as we want to undo what the code above >> did. The put_device here is for the get_device we did. The put_device >> in device_unregister is for the get_device that device_register did >> (on success only). >> >> Logically, it is wrong too to call unregister if register failed. That >> would be like doing this: > > You are right that the register and unregister are different devices. > However, your change is still wrong. The device_register is actually > irrelevant. > OK, the original order is right, it was my mistake. >> p = malloc(1); >> if (!p) >> free(p); >> >> This is the raw code: >> err = device_register(&bus->dev); >> if (err) >> goto unregister; >> unregister: >> put_device(&bridge->dev); >> device_del(&bridge->dev); > > The pertinent parts are this: > > err = device_add(&bridge->dev); // which calls get_device() itself, > so there's the first ref > if (err) { > put_device(&bridge->dev); > goto free; > } > bus->bridge = get_device(&bridge->dev); // This is the 2nd ref which > the PCI core holds > ... > unregister: > put_device(&bridge->dev); // This is the put for the get_device > just above here. > device_del(&bridge->dev); // Then this does the 2nd put. > > The get_device and put_device are paired, and the device_add and > device_del are paired. > > As I said earlier, go read the kerneldoc for device_add. For your > convenience, here's the important part: > > device_add: > * Rule of thumb is: if device_add() succeeds, you should call > * device_del() when you want to get rid of it. If device_add() has > * *not* succeeded, use *only* put_device() to drop the reference > * count. > > device_del: > * NOTE: this should be called manually _iff_ device_add() was > * also called manually. > > Rob ^ permalink raw reply [flat|nested] 7+ messages in thread
end of thread, other threads:[~2021-08-31 2:41 UTC | newest] Thread overview: 7+ messages (download: mbox.gz / follow: Atom feed) -- links below jump to the message on this page -- 2021-08-25 8:34 [PATCH linux-next] PCI: Fix the order in unregister path Yajun Deng 2021-08-25 13:55 ` Rob Herring 2021-08-26 3:57 ` yajun.deng 2021-08-26 12:01 ` Rob Herring 2021-08-27 2:39 ` yajun.deng 2021-08-30 14:55 ` Rob Herring 2021-08-31 2:41 ` yajun.deng
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