| Message ID | 20240524063023.77148-1-yaoma@linux.alibaba.com (mailing list archive) |
|---|---|
| State | Superseded |
| Delegated to: | Bjorn Helgaas |
| Headers | show |
| Series | PCI: pciehp: Use appropriate conditions to check the hotplug controller status | expand |
On Fri, May 24, 2024 at 02:30:23PM +0800, Bitao Hu wrote: > The values of 'present' and 'link_active' have similar meanings: > the value is %1 if the status is ready, and %0 if it is not. If the > hotplug controller itself is not available, the value should be > %-ENODEV. However, both %1 and %-ENODEV are considered true, which > obviously does not meet expectations. 'Slot(xx): Card present' and > 'Slot(xx): Link Up' should only be output when the value is %1. [...] > --- a/drivers/pci/hotplug/pciehp_ctrl.c > +++ b/drivers/pci/hotplug/pciehp_ctrl.c > @@ -276,10 +276,10 @@ void pciehp_handle_presence_or_link_change(struct controller *ctrl, u32 events) > case OFF_STATE: > ctrl->state = POWERON_STATE; > mutex_unlock(&ctrl->state_lock); > - if (present) > + if (present > 0) > ctrl_info(ctrl, "Slot(%s): Card present\n", > slot_name(ctrl)); > - if (link_active) > + if (link_active > 0) > ctrl_info(ctrl, "Slot(%s): Link Up\n", > slot_name(ctrl)); > ctrl->request_result = pciehp_enable_slot(ctrl); We already handle the "<= 0" case immediately above this code excerpt: if (present <= 0 && link_active <= 0) { ... } So neither "present" nor "link_active" can be < 0 at this point. Hence I don't quite understand what motivates the proposed code change? Thanks, Lukas
Hi, > 2024年5月24日 15:53，Lukas Wunner <lukas@wunner.de> 写道： > > On Fri, May 24, 2024 at 02:30:23PM +0800, Bitao Hu wrote: >> The values of 'present' and 'link_active' have similar meanings: >> the value is %1 if the status is ready, and %0 if it is not. If the >> hotplug controller itself is not available, the value should be >> %-ENODEV. However, both %1 and %-ENODEV are considered true, which >> obviously does not meet expectations. 'Slot(xx): Card present' and >> 'Slot(xx): Link Up' should only be output when the value is %1. > [...] >> --- a/drivers/pci/hotplug/pciehp_ctrl.c >> +++ b/drivers/pci/hotplug/pciehp_ctrl.c >> @@ -276,10 +276,10 @@ void pciehp_handle_presence_or_link_change(struct controller *ctrl, u32 events) >> case OFF_STATE: >> ctrl->state = POWERON_STATE; >> mutex_unlock(&ctrl->state_lock); >> - if (present) >> + if (present > 0) >> ctrl_info(ctrl, "Slot(%s): Card present\n", >> slot_name(ctrl)); >> - if (link_active) >> + if (link_active > 0) >> ctrl_info(ctrl, "Slot(%s): Link Up\n", >> slot_name(ctrl)); >> ctrl->request_result = pciehp_enable_slot(ctrl); > > We already handle the "<= 0" case immediately above this code excerpt: > > if (present <= 0 && link_active <= 0) { > ... > } I'm not sure if the following scenarios would occur in actual production environment, but from the code level, there is the possibility of “present <= 0 && link_active > 0” or “present > 0 && link_active <= 0”. In these cases, the “<= 0” conditions will not be properly handled, and “ctrl_info” will output incorrect prompt messages. > So neither "present" nor "link_active" can be < 0 at this point. > Best Regards, Bitao Hu
On Sun, May 26, 2024 at 10:45:36PM +0800, yaoma wrote: > > 2024 5 24 15:53 Lukas Wunner <lukas@wunner.de> > > On Fri, May 24, 2024 at 02:30:23PM +0800, Bitao Hu wrote: > > > The values of 'present' and 'link_active' have similar meanings: > > > the value is %1 if the status is ready, and %0 if it is not. If the > > > hotplug controller itself is not available, the value should be > > > %-ENODEV. However, both %1 and %-ENODEV are considered true, which > > > obviously does not meet expectations. 'Slot(xx): Card present' and > > > 'Slot(xx): Link Up' should only be output when the value is %1. > > [...] > > > --- a/drivers/pci/hotplug/pciehp_ctrl.c > > > +++ b/drivers/pci/hotplug/pciehp_ctrl.c > > > @@ -276,10 +276,10 @@ void pciehp_handle_presence_or_link_change(struct controller *ctrl, u32 events) > > > case OFF_STATE: > > > ctrl->state = POWERON_STATE; > > > mutex_unlock(&ctrl->state_lock); > > > - if (present) > > > + if (present > 0) > > > ctrl_info(ctrl, "Slot(%s): Card present\n", > > > slot_name(ctrl)); > > > - if (link_active) > > > + if (link_active > 0) > > > ctrl_info(ctrl, "Slot(%s): Link Up\n", > > > slot_name(ctrl)); > > > ctrl->request_result = pciehp_enable_slot(ctrl); > > > > We already handle the "<= 0" case immediately above this code excerpt: > > > > if (present <= 0 && link_active <= 0) { > > ... > > } > > I'm not sure if the following scenarios would occur in actual production > environment, but from the code level, there is the possibility of > "present <= 0 && link_active > 0" or "present > 0 && link_active <= 0". > In these cases, the "<= 0" conditions will not be properly handled, > and "ctrl_info" will output incorrect prompt messages. I see, that makes sense. "present" and "link_active" can be -ENODEV if reading the config space of the hotplug port failed. That's typically the case if the hotplug port itself was hot-removed, which happens all the time with Thunderbolt/USB4. E.g. pciehp_card_present() may return 1 and pciehp_check_link_active() may return -ENODEV because the hotplug port was hot-removed in-between the two function calls. In that case we'll emit both "Card present" *and* "Link Up". The latter is uncalled for and is supressed by your patch. So your code change is Reviewed-by: Lukas Wunner <lukas@wunner.de> ...but it would be good if you could respin the patch and explain the rationale of the code change in the commit message more clearly. Basically summarize what you and I have explained above. Also, the percent sign % in front of 0, 1, -ENODEV is unnecessary in commit messages. It only has special meaning in kernel-doc. Thanks, Lukas
Hi, > 2024年5月27日 16:50，Lukas Wunner <lukas@wunner.de> 写道： > > On Sun, May 26, 2024 at 10:45:36PM +0800, yaoma wrote: >>> 2024 5 24 15:53 Lukas Wunner <lukas@wunner.de> >>> On Fri, May 24, 2024 at 02:30:23PM +0800, Bitao Hu wrote: >>>> The values of 'present' and 'link_active' have similar meanings: >>>> the value is %1 if the status is ready, and %0 if it is not. If the >>>> hotplug controller itself is not available, the value should be >>>> %-ENODEV. However, both %1 and %-ENODEV are considered true, which >>>> obviously does not meet expectations. 'Slot(xx): Card present' and >>>> 'Slot(xx): Link Up' should only be output when the value is %1. >>> [...] >>>> --- a/drivers/pci/hotplug/pciehp_ctrl.c >>>> +++ b/drivers/pci/hotplug/pciehp_ctrl.c >>>> @@ -276,10 +276,10 @@ void pciehp_handle_presence_or_link_change(struct controller *ctrl, u32 events) >>>> case OFF_STATE: >>>> ctrl->state = POWERON_STATE; >>>> mutex_unlock(&ctrl->state_lock); >>>> - if (present) >>>> + if (present > 0) >>>> ctrl_info(ctrl, "Slot(%s): Card present\n", >>>> slot_name(ctrl)); >>>> - if (link_active) >>>> + if (link_active > 0) >>>> ctrl_info(ctrl, "Slot(%s): Link Up\n", >>>> slot_name(ctrl)); >>>> ctrl->request_result = pciehp_enable_slot(ctrl); >>> >>> We already handle the "<= 0" case immediately above this code excerpt: >>> >>> if (present <= 0 && link_active <= 0) { >>> ... >>> } >> >> I'm not sure if the following scenarios would occur in actual production >> environment, but from the code level, there is the possibility of >> "present <= 0 && link_active > 0" or "present > 0 && link_active <= 0". >> In these cases, the "<= 0" conditions will not be properly handled, >> and "ctrl_info" will output incorrect prompt messages. > > I see, that makes sense. > > "present" and "link_active" can be -ENODEV if reading the config space > of the hotplug port failed. That's typically the case if the hotplug > port itself was hot-removed, which happens all the time with > Thunderbolt/USB4. > > E.g. pciehp_card_present() may return 1 and pciehp_check_link_active() > may return -ENODEV because the hotplug port was hot-removed in-between > the two function calls. In that case we'll emit both "Card present" > *and* "Link Up". The latter is uncalled for and is supressed by your > patch. > > So your code change is > Reviewed-by: Lukas Wunner <lukas@wunner.de> > > ...but it would be good if you could respin the patch and explain the > rationale of the code change in the commit message more clearly. > Basically summarize what you and I have explained above. > > Also, the percent sign % in front of 0, 1, -ENODEV is unnecessary in > commit messages. It only has special meaning in kernel-doc. > Thanks for your analysis. I will make the the rationale of the code change more clearly in next patch. Best Regards, Bitao Hu
diff --git a/drivers/pci/hotplug/pciehp_ctrl.c b/drivers/pci/hotplug/pciehp_ctrl.c index dcdbfcf404dd..6adfdbb70150 100644 --- a/drivers/pci/hotplug/pciehp_ctrl.c +++ b/drivers/pci/hotplug/pciehp_ctrl.c @@ -276,10 +276,10 @@ void pciehp_handle_presence_or_link_change(struct controller *ctrl, u32 events) case OFF_STATE: ctrl->state = POWERON_STATE; mutex_unlock(&ctrl->state_lock); - if (present) + if (present > 0) ctrl_info(ctrl, "Slot(%s): Card present\n", slot_name(ctrl)); - if (link_active) + if (link_active > 0) ctrl_info(ctrl, "Slot(%s): Link Up\n", slot_name(ctrl)); ctrl->request_result = pciehp_enable_slot(ctrl);
The values of 'present' and 'link_active' have similar meanings: the value is %1 if the status is ready, and %0 if it is not. If the hotplug controller itself is not available, the value should be %-ENODEV. However, both %1 and %-ENODEV are considered true, which obviously does not meet expectations. 'Slot(xx): Card present' and 'Slot(xx): Link Up' should only be output when the value is %1. Signed-off-by: Bitao Hu <yaoma@linux.alibaba.com> --- drivers/pci/hotplug/pciehp_ctrl.c | 4 ++-- 1 file changed, 2 insertions(+), 2 deletions(-)