| Message ID | 20250401204425.904001-7-seanjc@google.com (mailing list archive) |
|---|---|
| State | Handled Elsewhere |
| Headers | show |
| Series | KVM: Make irqfd registration globally unique | expand |
| Context | Check | Description |
|---|---|---|
| bjorn/pre-ci_am | success | Success |
| bjorn/build-rv32-defconfig | success | build-rv32-defconfig |
| bjorn/build-rv64-clang-allmodconfig | fail | build-rv64-clang-allmodconfig |
| bjorn/build-rv64-gcc-allmodconfig | success | build-rv64-gcc-allmodconfig |
| bjorn/build-rv64-nommu-k210-defconfig | success | build-rv64-nommu-k210-defconfig |
| bjorn/build-rv64-nommu-k210-virt | success | build-rv64-nommu-k210-virt |
| bjorn/checkpatch | warning | checkpatch |
| bjorn/dtb-warn-rv64 | success | dtb-warn-rv64 |
| bjorn/header-inline | success | header-inline |
| bjorn/kdoc | success | kdoc |
| bjorn/module-param | success | module-param |
| bjorn/verify-fixes | success | verify-fixes |
| bjorn/verify-signedoff | success | verify-signedoff |
Hello Sean, On 4/2/2025 2:14 AM, Sean Christopherson wrote: [..snip..] > diff --git a/kernel/sched/wait.c b/kernel/sched/wait.c > index 51e38f5f4701..80d90d1dc24d 100644 > --- a/kernel/sched/wait.c > +++ b/kernel/sched/wait.c > @@ -47,6 +47,26 @@ void add_wait_queue_priority(struct wait_queue_head *wq_head, struct wait_queue_ > } > EXPORT_SYMBOL_GPL(add_wait_queue_priority); > > +int add_wait_queue_priority_exclusive(struct wait_queue_head *wq_head, > + struct wait_queue_entry *wq_entry) > +{ > + struct list_head *head = &wq_head->head; > + unsigned long flags; > + int r = 0; > + > + wq_entry->flags |= WQ_FLAG_EXCLUSIVE | WQ_FLAG_PRIORITY; > + spin_lock_irqsave(&wq_head->lock, flags); nit. Using "guard(spinlock_irqsave)(&wq_head->lock)" can help you get rid of both "flags" and "r". > + if (!list_empty(head) && > + (list_first_entry(head, typeof(*wq_entry), entry)->flags & WQ_FLAG_PRIORITY)) > + r = -EBUSY; > + else > + list_add(&wq_entry->entry, head); > + spin_unlock_irqrestore(&wq_head->lock, flags); > + > + return r; > +} > +EXPORT_SYMBOL(add_wait_queue_priority_exclusive); > + > void remove_wait_queue(struct wait_queue_head *wq_head, struct wait_queue_entry *wq_entry) > { > unsigned long flags;
diff --git a/include/linux/wait.h b/include/linux/wait.h index 6d90ad974408..5fe082c9e52b 100644 --- a/include/linux/wait.h +++ b/include/linux/wait.h @@ -164,6 +164,8 @@ static inline bool wq_has_sleeper(struct wait_queue_head *wq_head) extern void add_wait_queue(struct wait_queue_head *wq_head, struct wait_queue_entry *wq_entry); extern void add_wait_queue_exclusive(struct wait_queue_head *wq_head, struct wait_queue_entry *wq_entry); extern void add_wait_queue_priority(struct wait_queue_head *wq_head, struct wait_queue_entry *wq_entry); +extern int add_wait_queue_priority_exclusive(struct wait_queue_head *wq_head, + struct wait_queue_entry *wq_entry); extern void remove_wait_queue(struct wait_queue_head *wq_head, struct wait_queue_entry *wq_entry); static inline void __add_wait_queue(struct wait_queue_head *wq_head, struct wait_queue_entry *wq_entry) diff --git a/kernel/sched/wait.c b/kernel/sched/wait.c index 51e38f5f4701..80d90d1dc24d 100644 --- a/kernel/sched/wait.c +++ b/kernel/sched/wait.c @@ -47,6 +47,26 @@ void add_wait_queue_priority(struct wait_queue_head *wq_head, struct wait_queue_ } EXPORT_SYMBOL_GPL(add_wait_queue_priority); +int add_wait_queue_priority_exclusive(struct wait_queue_head *wq_head, + struct wait_queue_entry *wq_entry) +{ + struct list_head *head = &wq_head->head; + unsigned long flags; + int r = 0; + + wq_entry->flags |= WQ_FLAG_EXCLUSIVE | WQ_FLAG_PRIORITY; + spin_lock_irqsave(&wq_head->lock, flags); + if (!list_empty(head) && + (list_first_entry(head, typeof(*wq_entry), entry)->flags & WQ_FLAG_PRIORITY)) + r = -EBUSY; + else + list_add(&wq_entry->entry, head); + spin_unlock_irqrestore(&wq_head->lock, flags); + + return r; +} +EXPORT_SYMBOL(add_wait_queue_priority_exclusive); + void remove_wait_queue(struct wait_queue_head *wq_head, struct wait_queue_entry *wq_entry) { unsigned long flags;
Add a waitqueue helper to add a priority waiter that requires exclusive wakeups, i.e. that requires that it be the _only_ priority waiter. The API will be used by KVM to ensure that at most one of KVM's irqfds is bound to a single eventfd (across the entire kernel). Open code the helper instead of using __add_wait_queue() so that the common path doesn't need to "handle" impossible failures. Note, the priority_exclusive() name is obviously confusing as the plain priority() API also sets WQ_FLAG_EXCLUSIVE. This will be remedied once KVM switches to add_wait_queue_priority_exclusive(), as the only other user of add_wait_queue_priority(), Xen's privcmd, doesn't actually operate in exclusive mode (more than likely, the detail was overlooked when privcmd copy-pasted (sorry, "was inspired by") KVM's implementation). Signed-off-by: Sean Christopherson <seanjc@google.com> --- include/linux/wait.h | 2 ++ kernel/sched/wait.c | 20 ++++++++++++++++++++ 2 files changed, 22 insertions(+)