linux-kernel - [PATCH 08/12] sched/wait: Drop WQ_FLAG_EXCLUSIVE from add_wait_queue

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Message-ID: <20250401204425.904001-9-seanjc@google.com>
Date: Tue,  1 Apr 2025 13:44:20 -0700
From: Sean Christopherson <seanjc@...gle.com>
To: Paolo Bonzini <pbonzini@...hat.com>, Ingo Molnar <mingo@...hat.com>, 
	Peter Zijlstra <peterz@...radead.org>, Juri Lelli <juri.lelli@...hat.com>, 
	Vincent Guittot <vincent.guittot@...aro.org>, Marc Zyngier <maz@...nel.org>, 
	Oliver Upton <oliver.upton@...ux.dev>, Sean Christopherson <seanjc@...gle.com>, 
	Paul Walmsley <paul.walmsley@...ive.com>, Palmer Dabbelt <palmer@...belt.com>, 
	Albert Ou <aou@...s.berkeley.edu>
Cc: kvm@...r.kernel.org, linux-kernel@...r.kernel.org, 
	linux-arm-kernel@...ts.infradead.org, kvmarm@...ts.linux.dev, 
	linux-riscv@...ts.infradead.org, David Matlack <dmatlack@...gle.com>, 
	Juergen Gross <jgross@...e.com>, Stefano Stabellini <sstabellini@...nel.org>, 
	Oleksandr Tyshchenko <oleksandr_tyshchenko@...m.com>
Subject: [PATCH 08/12] sched/wait: Drop WQ_FLAG_EXCLUSIVE from add_wait_queue_priority()

Drop the setting of WQ_FLAG_EXCLUSIVE from add_wait_queue_priority() to
differentiate it from add_wait_queue_priority_exclusive().  The one and
only user add_wait_queue_priority(), Xen privcmd's irqfd_wakeup(),
unconditionally returns '0', i.e. doesn't actually operate in exclusive
mode.

Cc: Juergen Gross <jgross@...e.com>
Cc: Stefano Stabellini <sstabellini@...nel.org>
Cc: Oleksandr Tyshchenko <oleksandr_tyshchenko@...m.com>
Signed-off-by: Sean Christopherson <seanjc@...gle.com>
---
 kernel/sched/wait.c | 4 ++--
 1 file changed, 2 insertions(+), 2 deletions(-)

diff --git a/kernel/sched/wait.c b/kernel/sched/wait.c
index 80d90d1dc24d..2af0fc92e5d3 100644
--- a/kernel/sched/wait.c
+++ b/kernel/sched/wait.c
@@ -40,7 +40,7 @@ void add_wait_queue_priority(struct wait_queue_head *wq_head, struct wait_queue_
 {
 	unsigned long flags;
 
-	wq_entry->flags |= WQ_FLAG_EXCLUSIVE | WQ_FLAG_PRIORITY;
+	wq_entry->flags |= WQ_FLAG_PRIORITY;
 	spin_lock_irqsave(&wq_head->lock, flags);
 	__add_wait_queue(wq_head, wq_entry);
 	spin_unlock_irqrestore(&wq_head->lock, flags);
@@ -84,7 +84,7 @@ EXPORT_SYMBOL(remove_wait_queue);
  * the non-exclusive tasks. Normally, exclusive tasks will be at the end of
  * the list and any non-exclusive tasks will be woken first. A priority task
  * may be at the head of the list, and can consume the event without any other
- * tasks being woken.
+ * tasks being woken if it's also an exclusive task.
  *
  * There are circumstances in which we can try to wake a task which has already
  * started to run but is not in state TASK_RUNNING. try_to_wake_up() returns
-- 
2.49.0.504.g3bcea36a83-goog