| Message ID | 20191119011545.15408-1-zhengxiang9@huawei.com (mailing list archive) |
|---|---|
| State | Superseded, archived |
| Headers | show |
| Series | [v2] pci: lock the pci_cfg_wait queue for the consistency of data | expand |
On Tue, Nov 19, 2019 at 09:15:45AM +0800, Xiang Zheng wrote: > Commit "7ea7e98fd8d0" suggests that the "pci_lock" is sufficient, > and all the callers of pci_wait_cfg() are wrapped with the "pci_lock". > > However, since the commit "cdcb33f98244" merged, the accesses to > the pci_cfg_wait queue are not safe anymore. A "pci_lock" is > insufficient and we need to hold an additional queue lock while > read/write the wait queue. > > So let's use the add_wait_queue()/remove_wait_queue() instead of > __add_wait_queue()/__remove_wait_queue(). Also move the wait queue > functionality around the "schedule()" function to avoid reintroducing > the deadlock addressed by "cdcb33f98244". Procedural nits: - Run "git log --oneline drivers/pci/access.c" and follow the convention, e.g., starts with "PCI: " and first subsequent word is capitalized. - Use conventional commit references, e.g., 7ea7e98fd8d0 ("PCI: Block on access to temporarily unavailable pci device") and cdcb33f98244 ("PCI: Avoid possible deadlock on pci_lock and p->pi_lock") - IIRC you found that this actually caused a panic; please include the lore.kernel.org URL to that report. You can wait for a while to see if there are more substantive comments to address before posting a v3. > Signed-off-by: Xiang Zheng <zhengxiang9@huawei.com> > Cc: Heyi Guo <guoheyi@huawei.com> > Cc: Biaoxiang Ye <yebiaoxiang@huawei.com> > --- > > v2: > - Move the wait queue functionality around the "schedule()" function to > avoid reintroducing the deadlock addressed by "cdcb33f98244" > > --- > > drivers/pci/access.c | 4 ++-- > 1 file changed, 2 insertions(+), 2 deletions(-) > > diff --git a/drivers/pci/access.c b/drivers/pci/access.c > index 2fccb5762c76..09342a74e5ea 100644 > --- a/drivers/pci/access.c > +++ b/drivers/pci/access.c > @@ -207,14 +207,14 @@ static noinline void pci_wait_cfg(struct pci_dev *dev) > { > DECLARE_WAITQUEUE(wait, current); > > - __add_wait_queue(&pci_cfg_wait, &wait); > do { > set_current_state(TASK_UNINTERRUPTIBLE); > raw_spin_unlock_irq(&pci_lock); > + add_wait_queue(&pci_cfg_wait, &wait); > schedule(); > + remove_wait_queue(&pci_cfg_wait, &wait); > raw_spin_lock_irq(&pci_lock); > } while (dev->block_cfg_access); > - __remove_wait_queue(&pci_cfg_wait, &wait); > } > > /* Returns 0 on success, negative values indicate error. */ > -- > 2.19.1 > >
On 2019/11/20 4:23, Bjorn Helgaas wrote: > On Tue, Nov 19, 2019 at 09:15:45AM +0800, Xiang Zheng wrote: >> Commit "7ea7e98fd8d0" suggests that the "pci_lock" is sufficient, >> and all the callers of pci_wait_cfg() are wrapped with the "pci_lock". >> >> However, since the commit "cdcb33f98244" merged, the accesses to >> the pci_cfg_wait queue are not safe anymore. A "pci_lock" is >> insufficient and we need to hold an additional queue lock while >> read/write the wait queue. >> >> So let's use the add_wait_queue()/remove_wait_queue() instead of >> __add_wait_queue()/__remove_wait_queue(). Also move the wait queue >> functionality around the "schedule()" function to avoid reintroducing >> the deadlock addressed by "cdcb33f98244". > > Procedural nits: > > - Run "git log --oneline drivers/pci/access.c" and follow the > convention, e.g., starts with "PCI: " and first subsequent word is > capitalized. > > - Use conventional commit references, e.g., 7ea7e98fd8d0 ("PCI: > Block on access to temporarily unavailable pci device") and > cdcb33f98244 ("PCI: Avoid possible deadlock on pci_lock and > p->pi_lock") > > - IIRC you found that this actually caused a panic; please include > the lore.kernel.org URL to that report. > Got it, I will address these nits. > You can wait for a while to see if there are more substantive comments > to address before posting a v3. > OK. >> Signed-off-by: Xiang Zheng <zhengxiang9@huawei.com> >> Cc: Heyi Guo <guoheyi@huawei.com> >> Cc: Biaoxiang Ye <yebiaoxiang@huawei.com> >> --- >> >> v2: >> - Move the wait queue functionality around the "schedule()" function to >> avoid reintroducing the deadlock addressed by "cdcb33f98244" >> >> --- >> >> drivers/pci/access.c | 4 ++-- >> 1 file changed, 2 insertions(+), 2 deletions(-) >> >> diff --git a/drivers/pci/access.c b/drivers/pci/access.c >> index 2fccb5762c76..09342a74e5ea 100644 >> --- a/drivers/pci/access.c >> +++ b/drivers/pci/access.c >> @@ -207,14 +207,14 @@ static noinline void pci_wait_cfg(struct pci_dev *dev) >> { >> DECLARE_WAITQUEUE(wait, current); >> >> - __add_wait_queue(&pci_cfg_wait, &wait); >> do { >> set_current_state(TASK_UNINTERRUPTIBLE); >> raw_spin_unlock_irq(&pci_lock); >> + add_wait_queue(&pci_cfg_wait, &wait); >> schedule(); >> + remove_wait_queue(&pci_cfg_wait, &wait); >> raw_spin_lock_irq(&pci_lock); >> } while (dev->block_cfg_access); >> - __remove_wait_queue(&pci_cfg_wait, &wait); >> } >> >> /* Returns 0 on success, negative values indicate error. */ >> -- >> 2.19.1 >> >> > > . >
diff --git a/drivers/pci/access.c b/drivers/pci/access.c index 2fccb5762c76..09342a74e5ea 100644 --- a/drivers/pci/access.c +++ b/drivers/pci/access.c @@ -207,14 +207,14 @@ static noinline void pci_wait_cfg(struct pci_dev *dev) { DECLARE_WAITQUEUE(wait, current); - __add_wait_queue(&pci_cfg_wait, &wait); do { set_current_state(TASK_UNINTERRUPTIBLE); raw_spin_unlock_irq(&pci_lock); + add_wait_queue(&pci_cfg_wait, &wait); schedule(); + remove_wait_queue(&pci_cfg_wait, &wait); raw_spin_lock_irq(&pci_lock); } while (dev->block_cfg_access); - __remove_wait_queue(&pci_cfg_wait, &wait); } /* Returns 0 on success, negative values indicate error. */
Commit "7ea7e98fd8d0" suggests that the "pci_lock" is sufficient, and all the callers of pci_wait_cfg() are wrapped with the "pci_lock". However, since the commit "cdcb33f98244" merged, the accesses to the pci_cfg_wait queue are not safe anymore. A "pci_lock" is insufficient and we need to hold an additional queue lock while read/write the wait queue. So let's use the add_wait_queue()/remove_wait_queue() instead of __add_wait_queue()/__remove_wait_queue(). Also move the wait queue functionality around the "schedule()" function to avoid reintroducing the deadlock addressed by "cdcb33f98244". Signed-off-by: Xiang Zheng <zhengxiang9@huawei.com> Cc: Heyi Guo <guoheyi@huawei.com> Cc: Biaoxiang Ye <yebiaoxiang@huawei.com> --- v2: - Move the wait queue functionality around the "schedule()" function to avoid reintroducing the deadlock addressed by "cdcb33f98244" --- drivers/pci/access.c | 4 ++-- 1 file changed, 2 insertions(+), 2 deletions(-)