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From: Sean Christopherson <seanjc@google.com>
To: Paolo Bonzini <pbonzini@redhat.com>,
	Ingo Molnar <mingo@redhat.com>,
	 Peter Zijlstra <peterz@infradead.org>,
	Juri Lelli <juri.lelli@redhat.com>,
	 Vincent Guittot <vincent.guittot@linaro.org>,
	Marc Zyngier <maz@kernel.org>,
	 Oliver Upton <oliver.upton@linux.dev>,
	Sean Christopherson <seanjc@google.com>,
	 Paul Walmsley <paul.walmsley@sifive.com>,
	Palmer Dabbelt <palmer@dabbelt.com>,
	 Albert Ou <aou@eecs.berkeley.edu>
Cc: kvm@vger.kernel.org, linux-kernel@vger.kernel.org,
	 linux-arm-kernel@lists.infradead.org, kvmarm@lists.linux.dev,
	 linux-riscv@lists.infradead.org,
	David Matlack <dmatlack@google.com>,
	 Juergen Gross <jgross@suse.com>,
	Stefano Stabellini <sstabellini@kernel.org>,
	 Oleksandr Tyshchenko <oleksandr_tyshchenko@epam.com>
Subject: [PATCH 08/12] sched/wait: Drop WQ_FLAG_EXCLUSIVE from add_wait_queue_priority()
Date: Tue,  1 Apr 2025 13:44:20 -0700	[thread overview]
Message-ID: <20250401204425.904001-9-seanjc@google.com> (raw)
In-Reply-To: <20250401204425.904001-1-seanjc@google.com>

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@suse.com>
Cc: Stefano Stabellini <sstabellini@kernel.org>
Cc: Oleksandr Tyshchenko <oleksandr_tyshchenko@epam.com>
Signed-off-by: Sean Christopherson <seanjc@google.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


WARNING: multiple messages have this Message-ID (diff)
From: Sean Christopherson <seanjc@google.com>
To: Paolo Bonzini <pbonzini@redhat.com>,
	Ingo Molnar <mingo@redhat.com>,
	 Peter Zijlstra <peterz@infradead.org>,
	Juri Lelli <juri.lelli@redhat.com>,
	 Vincent Guittot <vincent.guittot@linaro.org>,
	Marc Zyngier <maz@kernel.org>,
	 Oliver Upton <oliver.upton@linux.dev>,
	Sean Christopherson <seanjc@google.com>,
	 Paul Walmsley <paul.walmsley@sifive.com>,
	Palmer Dabbelt <palmer@dabbelt.com>,
	 Albert Ou <aou@eecs.berkeley.edu>
Cc: kvm@vger.kernel.org, linux-kernel@vger.kernel.org,
	 linux-arm-kernel@lists.infradead.org, kvmarm@lists.linux.dev,
	 linux-riscv@lists.infradead.org,
	David Matlack <dmatlack@google.com>,
	 Juergen Gross <jgross@suse.com>,
	Stefano Stabellini <sstabellini@kernel.org>,
	 Oleksandr Tyshchenko <oleksandr_tyshchenko@epam.com>
Subject: [PATCH 08/12] sched/wait: Drop WQ_FLAG_EXCLUSIVE from add_wait_queue_priority()
Date: Tue,  1 Apr 2025 13:44:20 -0700	[thread overview]
Message-ID: <20250401204425.904001-9-seanjc@google.com> (raw)
In-Reply-To: <20250401204425.904001-1-seanjc@google.com>

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@suse.com>
Cc: Stefano Stabellini <sstabellini@kernel.org>
Cc: Oleksandr Tyshchenko <oleksandr_tyshchenko@epam.com>
Signed-off-by: Sean Christopherson <seanjc@google.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


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  parent reply	other threads:[~2025-04-01 20:47 UTC|newest]

Thread overview: 28+ messages / expand[flat|nested]  mbox.gz  Atom feed  top
2025-04-01 20:44 [PATCH 00/12] KVM: Make irqfd registration globally unique Sean Christopherson
2025-04-01 20:44 ` Sean Christopherson
2025-04-01 20:44 ` [PATCH 01/12] KVM: Use a local struct to do the initial vfs_poll() on an irqfd Sean Christopherson
2025-04-01 20:44   ` Sean Christopherson
2025-04-01 20:44 ` [PATCH 02/12] KVM: Acquire SCRU lock outside of irqfds.lock during assignment Sean Christopherson
2025-04-01 20:44   ` Sean Christopherson
2025-04-01 20:44 ` [PATCH 03/12] KVM: Initialize irqfd waitqueue callback when adding to the queue Sean Christopherson
2025-04-01 20:44   ` Sean Christopherson
2025-04-01 20:44 ` [PATCH 04/12] KVM: Add irqfd to KVM's list via the vfs_poll() callback Sean Christopherson
2025-04-01 20:44   ` Sean Christopherson
2025-04-01 20:44 ` [PATCH 05/12] KVM: Add irqfd to eventfd's waitqueue while holding irqfds.lock Sean Christopherson
2025-04-01 20:44   ` Sean Christopherson
2025-04-01 20:44 ` [PATCH 06/12] sched/wait: Add a waitqueue helper for fully exclusive priority waiters Sean Christopherson
2025-04-01 20:44   ` Sean Christopherson
2025-04-02 18:40   ` K Prateek Nayak
2025-04-02 18:40     ` K Prateek Nayak
2025-04-01 20:44 ` [PATCH 07/12] KVM: Disallow binding multiple irqfds to an eventfd with a priority waiter Sean Christopherson
2025-04-01 20:44   ` Sean Christopherson
2025-04-01 20:44 ` Sean Christopherson [this message]
2025-04-01 20:44   ` [PATCH 08/12] sched/wait: Drop WQ_FLAG_EXCLUSIVE from add_wait_queue_priority() Sean Christopherson
2025-04-01 20:44 ` [PATCH 09/12] KVM: Drop sanity check that per-VM list of irqfds is unique Sean Christopherson
2025-04-01 20:44   ` Sean Christopherson
2025-04-01 20:44 ` [PATCH 10/12] KVM: selftests: Assert that eventfd() succeeds in Xen shinfo test Sean Christopherson
2025-04-01 20:44   ` Sean Christopherson
2025-04-01 20:44 ` [PATCH 11/12] KVM: selftests: Add utilities to create eventfds and do KVM_IRQFD Sean Christopherson
2025-04-01 20:44   ` Sean Christopherson
2025-04-01 20:44 ` [PATCH 12/12] KVM: selftests: Add a KVM_IRQFD test to verify uniqueness requirements Sean Christopherson
2025-04-01 20:44   ` Sean Christopherson

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