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From: Nitesh Narayan Lal <nitesh@redhat.com>
To: linux-kernel@vger.kernel.org, linux-scsi@vger.kernel.org,
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Subject: [PATCH v5 01/14] genirq: Provide new interfaces for affinity hints
Date: Tue, 20 Jul 2021 19:26:11 -0400	[thread overview]
Message-ID: <20210720232624.1493424-2-nitesh@redhat.com> (raw)
In-Reply-To: <20210720232624.1493424-1-nitesh@redhat.com>

From: Thomas Gleixner <tglx@linutronix.de>

The discussion about removing the side effect of irq_set_affinity_hint() of
actually applying the cpumask (if not NULL) as affinity to the interrupt,
unearthed a few unpleasantries:

  1) The modular perf drivers rely on the current behaviour for the very
     wrong reasons.

  2) While none of the other drivers prevents user space from changing
     the affinity, a cursorily inspection shows that there are at least
     expectations in some drivers.

#1 needs to be cleaned up anyway, so that's not a problem

#2 might result in subtle regressions especially when irqbalanced (which
   nowadays ignores the affinity hint) is disabled.

Provide new interfaces:

  irq_update_affinity_hint()  - Only sets the affinity hint pointer
  irq_set_affinity_and_hint() - Set the pointer and apply the affinity to
                                the interrupt

Make irq_set_affinity_hint() a wrapper around irq_apply_affinity_hint() and
document it to be phased out.

Signed-off-by: Thomas Gleixner <tglx@linutronix.de>
Signed-off-by: Nitesh Narayan Lal <nitesh@redhat.com>
Link: https://lore.kernel.org/r/20210501021832.743094-1-jesse.brandeburg@intel.com
---
 include/linux/interrupt.h | 53 ++++++++++++++++++++++++++++++++++++++-
 kernel/irq/manage.c       |  8 +++---
 2 files changed, 56 insertions(+), 5 deletions(-)

diff --git a/include/linux/interrupt.h b/include/linux/interrupt.h
index 2ed65b01c961..c2563a9321d7 100644
--- a/include/linux/interrupt.h
+++ b/include/linux/interrupt.h
@@ -328,7 +328,46 @@ extern int irq_force_affinity(unsigned int irq, const struct cpumask *cpumask);
 extern int irq_can_set_affinity(unsigned int irq);
 extern int irq_select_affinity(unsigned int irq);
 
-extern int irq_set_affinity_hint(unsigned int irq, const struct cpumask *m);
+extern int __irq_apply_affinity_hint(unsigned int irq, const struct cpumask *m,
+				     bool setaffinity);
+
+/**
+ * irq_update_affinity_hint - Update the affinity hint
+ * @irq:	Interrupt to update
+ * @m:		cpumask pointer (NULL to clear the hint)
+ *
+ * Updates the affinity hint, but does not change the affinity of the interrupt.
+ */
+static inline int
+irq_update_affinity_hint(unsigned int irq, const struct cpumask *m)
+{
+	return __irq_apply_affinity_hint(irq, m, false);
+}
+
+/**
+ * irq_set_affinity_and_hint - Update the affinity hint and apply the provided
+ *			     cpumask to the interrupt
+ * @irq:	Interrupt to update
+ * @m:		cpumask pointer (NULL to clear the hint)
+ *
+ * Updates the affinity hint and if @m is not NULL it applies it as the
+ * affinity of that interrupt.
+ */
+static inline int
+irq_set_affinity_and_hint(unsigned int irq, const struct cpumask *m)
+{
+	return __irq_apply_affinity_hint(irq, m, true);
+}
+
+/*
+ * Deprecated. Use irq_update_affinity_hint() or irq_set_affinity_and_hint()
+ * instead.
+ */
+static inline int irq_set_affinity_hint(unsigned int irq, const struct cpumask *m)
+{
+	return irq_set_affinity_and_hint(irq, m);
+}
+
 extern int irq_update_affinity_desc(unsigned int irq,
 				    struct irq_affinity_desc *affinity);
 
@@ -360,6 +399,18 @@ static inline int irq_can_set_affinity(unsigned int irq)
 
 static inline int irq_select_affinity(unsigned int irq)  { return 0; }
 
+static inline int irq_update_affinity_hint(unsigned int irq,
+					   const struct cpumask *m)
+{
+	return -EINVAL;
+}
+
+static inline int irq_set_affinity_and_hint(unsigned int irq,
+					    const struct cpumask *m)
+{
+	return -EINVAL;
+}
+
 static inline int irq_set_affinity_hint(unsigned int irq,
 					const struct cpumask *m)
 {
diff --git a/kernel/irq/manage.c b/kernel/irq/manage.c
index ef30b4762947..837b63e63111 100644
--- a/kernel/irq/manage.c
+++ b/kernel/irq/manage.c
@@ -487,7 +487,8 @@ int irq_force_affinity(unsigned int irq, const struct cpumask *cpumask)
 }
 EXPORT_SYMBOL_GPL(irq_force_affinity);
 
-int irq_set_affinity_hint(unsigned int irq, const struct cpumask *m)
+int __irq_apply_affinity_hint(unsigned int irq, const struct cpumask *m,
+			      bool setaffinity)
 {
 	unsigned long flags;
 	struct irq_desc *desc = irq_get_desc_lock(irq, &flags, IRQ_GET_DESC_CHECK_GLOBAL);
@@ -496,12 +497,11 @@ int irq_set_affinity_hint(unsigned int irq, const struct cpumask *m)
 		return -EINVAL;
 	desc->affinity_hint = m;
 	irq_put_desc_unlock(desc, flags);
-	/* set the initial affinity to prevent every interrupt being on CPU0 */
-	if (m)
+	if (m && setaffinity)
 		__irq_set_affinity(irq, m, false);
 	return 0;
 }
-EXPORT_SYMBOL_GPL(irq_set_affinity_hint);
+EXPORT_SYMBOL_GPL(__irq_apply_affinity_hint);
 
 static void irq_affinity_notify(struct work_struct *work)
 {
-- 
2.27.0


  reply	other threads:[~2021-07-20 23:28 UTC|newest]

Thread overview: 28+ messages / expand[flat|nested]  mbox.gz  Atom feed  top
2021-07-20 23:26 [PATCH v5 00/14] genirq: Cleanup the abuse of irq_set_affinity_hint() Nitesh Narayan Lal
2021-07-20 23:26 ` Nitesh Narayan Lal [this message]
2021-08-06 15:51   ` [PATCH v5 01/14] genirq: Provide new interfaces for affinity hints Ming Lei
2021-07-20 23:26 ` [PATCH v5 02/14] iavf: Use irq_update_affinity_hint Nitesh Narayan Lal
2021-07-20 23:26 ` [PATCH v5 03/14] i40e: " Nitesh Narayan Lal
2021-07-20 23:26 ` [PATCH v5 04/14] scsi: megaraid_sas: Use irq_set_affinity_and_hint Nitesh Narayan Lal
2021-08-06 11:31   ` Sumit Saxena
2021-07-20 23:26 ` [PATCH v5 05/14] scsi: mpt3sas: " Nitesh Narayan Lal
2021-08-06  8:54   ` Sreekanth Reddy
2021-07-20 23:26 ` [PATCH v5 06/14] RDMA/irdma: Use irq_update_affinity_hint Nitesh Narayan Lal
2021-07-22 18:25   ` Nikolova, Tatyana E
2021-07-20 23:26 ` [PATCH v5 07/14] enic: " Nitesh Narayan Lal
2021-08-16 17:53   ` Christian Benvenuti (benve)
2021-07-20 23:26 ` [PATCH v5 08/14] be2net: " Nitesh Narayan Lal
2021-07-20 23:26 ` [PATCH v5 09/14] ixgbe: " Nitesh Narayan Lal
2021-07-20 23:26 ` [PATCH v5 10/14] mailbox: " Nitesh Narayan Lal
2021-08-16 18:11   ` Jassi Brar
2021-07-20 23:26 ` [PATCH v5 11/14] scsi: lpfc: Use irq_set_affinity Nitesh Narayan Lal
2021-07-23 17:15   ` James Smart
2021-07-20 23:26 ` [PATCH v5 12/14] hinic: Use irq_set_affinity_and_hint Nitesh Narayan Lal
2021-07-20 23:26 ` [PATCH v5 13/14] net/mlx5: " Nitesh Narayan Lal
2021-07-20 23:26 ` [PATCH v5 14/14] net/mlx4: Use irq_update_affinity_hint Nitesh Narayan Lal
2021-08-02 15:26 ` [PATCH v5 00/14] genirq: Cleanup the abuse of irq_set_affinity_hint() Nitesh Lal
2021-08-06  3:04   ` Martin K. Petersen
2021-08-06 14:56     ` Nitesh Lal
2021-08-16 15:50   ` Nitesh Lal
2021-08-30 15:38     ` Nitesh Lal
2021-08-30 15:40       ` Nitesh Lal

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