diff options
| author | Sean Christopherson <seanjc@google.com> | 2025-05-22 16:52:18 -0700 |
|---|---|---|
| committer | Sean Christopherson <seanjc@google.com> | 2025-06-23 09:50:58 -0700 |
| commit | 0d09582b3a607436fd91d6ce813048a048ecbf10 (patch) | |
| tree | 5e8d7a18bf471c026f94c190b365d040ba1eec40 | |
| parent | a52664134a24f3b0c425781082ce993617fc2797 (diff) | |
sched/wait: Add a waitqueue helper for fully exclusive priority waiters
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.
Cc: K Prateek Nayak <kprateek.nayak@amd.com>
Reviewed-by: K Prateek Nayak <kprateek.nayak@amd.com>
Tested-by: K Prateek Nayak <kprateek.nayak@amd.com>
Acked-by: Peter Zijlstra (Intel) <peterz@infradead.org>
Link: https://lore.kernel.org/r/20250522235223.3178519-9-seanjc@google.com
Signed-off-by: Sean Christopherson <seanjc@google.com>
| -rw-r--r-- | include/linux/wait.h | 2 | ||||
| -rw-r--r-- | kernel/sched/wait.c | 18 |
2 files changed, 20 insertions, 0 deletions
diff --git a/include/linux/wait.h b/include/linux/wait.h index 965a19809c7e..09855d819418 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 4ab3ab195277..15632c89c4f2 100644 --- a/kernel/sched/wait.c +++ b/kernel/sched/wait.c @@ -47,6 +47,24 @@ 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; + + wq_entry->flags |= WQ_FLAG_EXCLUSIVE | WQ_FLAG_PRIORITY; + + guard(spinlock_irqsave)(&wq_head->lock); + + if (!list_empty(head) && + (list_first_entry(head, typeof(*wq_entry), entry)->flags & WQ_FLAG_PRIORITY)) + return -EBUSY; + + list_add(&wq_entry->entry, head); + return 0; +} +EXPORT_SYMBOL_GPL(add_wait_queue_priority_exclusive); + void remove_wait_queue(struct wait_queue_head *wq_head, struct wait_queue_entry *wq_entry) { unsigned long flags; |