linux-kernel - [PATCH 4.4 330/342] x86/irq: Get rid of code duplication

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Date:	Tue, 01 Mar 2016 23:55:35 +0000
From:	Greg Kroah-Hartman <gregkh@...uxfoundation.org>
To:	<linux-kernel@...r.kernel.org>
Cc:	Greg Kroah-Hartman <gregkh@...uxfoundation.org>,
	<stable@...r.kernel.org>, Thomas Gleixner <tglx@...utronix.de>,
	Borislav Petkov <bp@...en8.de>,
	Joe Lawrence <joe.lawrence@...atus.com>,
	Jiang Liu <jiang.liu@...ux.intel.com>,
	Jeremiah Mahler <jmmahler@...il.com>,
	<andy.shevchenko@...il.com>, Guenter Roeck <linux@...ck-us.net>
Subject: [PATCH 4.4 330/342] x86/irq: Get rid of code duplication

4.4-stable review patch.  If anyone has any objections, please let me know.

------------------

From: Thomas Gleixner <tglx@...utronix.de>

commit ab25ac02148b600e645f77cfb8b8ea415ed75bb4 upstream.

Reusing an existing vector and assigning a new vector has duplicated
code. Consolidate it.

This is also a preparatory patch for finally plugging the cleanup race.

Signed-off-by: Thomas Gleixner <tglx@...utronix.de>
Tested-by: Borislav Petkov <bp@...en8.de>
Tested-by: Joe Lawrence <joe.lawrence@...atus.com>
Cc: Jiang Liu <jiang.liu@...ux.intel.com>
Cc: Jeremiah Mahler <jmmahler@...il.com>
Cc: andy.shevchenko@...il.com
Cc: Guenter Roeck <linux@...ck-us.net>
Link: http://lkml.kernel.org/r/20151231160106.721599216@linutronix.de
Signed-off-by: Thomas Gleixner <tglx@...utronix.de>
Signed-off-by: Greg Kroah-Hartman <gregkh@...uxfoundation.org>

---
 arch/x86/kernel/apic/vector.c |   33 +++++++++++++++------------------
 1 file changed, 15 insertions(+), 18 deletions(-)

--- a/arch/x86/kernel/apic/vector.c
+++ b/arch/x86/kernel/apic/vector.c
@@ -116,7 +116,7 @@ static int __assign_irq_vector(int irq,
 	 */
 	static int current_vector = FIRST_EXTERNAL_VECTOR + VECTOR_OFFSET_START;
 	static int current_offset = VECTOR_OFFSET_START % 16;
-	int cpu;
+	int cpu, vector;
 
 	if (d->move_in_progress)
 		return -EBUSY;
@@ -126,7 +126,7 @@ static int __assign_irq_vector(int irq,
 	cpumask_clear(searched_cpumask);
 	cpu = cpumask_first_and(mask, cpu_online_mask);
 	while (cpu < nr_cpu_ids) {
-		int new_cpu, vector, offset;
+		int new_cpu, offset;
 
 		/* Get the possible target cpus for @mask/@cpu from the apic */
 		apic->vector_allocation_domain(cpu, vector_cpumask, mask);
@@ -146,16 +146,12 @@ static int __assign_irq_vector(int irq,
 			if (cpumask_equal(vector_cpumask, d->domain))
 				goto success;
 			/*
-			 * New cpumask using the vector is a proper subset of
-			 * the current in use mask. So cleanup the vector
-			 * allocation for the members that are not used anymore.
+			 * Mark the cpus which are not longer in the mask for
+			 * cleanup.
 			 */
-			cpumask_andnot(d->old_domain, d->domain,
-				       vector_cpumask);
-			d->move_in_progress =
-			   cpumask_intersects(d->old_domain, cpu_online_mask);
-			cpumask_copy(d->domain, vector_cpumask);
-			goto success;
+			cpumask_andnot(d->old_domain, d->domain, vector_cpumask);
+			vector = d->cfg.vector;
+			goto update;
 		}
 
 		vector = current_vector;
@@ -181,16 +177,12 @@ next:
 		/* Found one! */
 		current_vector = vector;
 		current_offset = offset;
-		if (d->cfg.vector) {
+		/* Schedule the old vector for cleanup on all cpus */
+		if (d->cfg.vector)
 			cpumask_copy(d->old_domain, d->domain);
-			d->move_in_progress =
-			   cpumask_intersects(d->old_domain, cpu_online_mask);
-		}
 		for_each_cpu(new_cpu, vector_searchmask)
 			per_cpu(vector_irq, new_cpu)[vector] = irq_to_desc(irq);
-		d->cfg.vector = vector;
-		cpumask_copy(d->domain, vector_cpumask);
-		goto success;
+		goto update;
 
 next_cpu:
 		/*
@@ -207,6 +199,11 @@ next_cpu:
 	}
 	return -ENOSPC;
 
+update:
+	/* Cleanup required ? */
+	d->move_in_progress = cpumask_intersects(d->old_domain, cpu_online_mask);
+	d->cfg.vector = vector;
+	cpumask_copy(d->domain, vector_cpumask);
 success:
 	/*
 	 * Cache destination APIC IDs into cfg->dest_apicid. This cannot fail