Patch "genirq/matrix: Handle CPU offlining proper" has been added to the 4.15-stable tree

This is a note to let you know that I've just added the patch titled

genirq/matrix: Handle CPU offlining proper

to the 4.15-stable tree which can be found at:
http://www.kernel.org/git/?p=linux/kernel/git/stable/stable-queue.git;a=summary

The filename of the patch is:
genirq-matrix-handle-cpu-offlining-proper.patch
and it can be found in the queue-4.15 subdirectory.

If you, or anyone else, feels it should not be added to the stable tree, please let <[email protected]> know about it.

From: Thomas Gleixner <[email protected]>
Date: Thu, 22 Feb 2018 12:08:05 +0100
Subject: genirq/matrix: Handle CPU offlining proper

From: Thomas Gleixner <[email protected]>

commit 651ca2c00405a2ae3870cc0b4f15a182eb6fbe26 upstream.

At CPU hotunplug the corresponding per cpu matrix allocator is shut down and the allocated interrupt bits are discarded under the assumption that all allocated bits have been either migrated away or shut down through the managed interrupts mechanism.

This is not true because interrupts which are not started up might have a vector allocated on the outgoing CPU. When the interrupt is started up later or completely shutdown and freed then the allocated vector is handed back, triggering warnings or causing accounting issues which result in suspend failures and other issues.

Change the CPU hotplug mechanism of the matrix allocator so that the remaining allocations at unplug time are preserved and global accounting at hotplug is correctly readjusted to take the dormant vectors into account.

---
 kernel/irq/matrix.c |   23 ++++++++++++++---------
 1 file changed, 14 insertions(+), 9 deletions(-)

@@ -16,6 +16,7 @@ struct cpumap {
 	unsigned int		available;
 	unsigned int		allocated;
 	unsigned int		managed;
+	bool			initialized;
 	bool			online;
 	unsigned long		alloc_map[IRQ_MATRIX_SIZE];
 	unsigned long		managed_map[IRQ_MATRIX_SIZE];

@@ -81,9 +82,11 @@ void irq_matrix_online(struct irq_matrix
 
 	BUG_ON(cm->online);
 
-	bitmap_zero(cm->alloc_map, m->matrix_bits);
-	cm->available = m->alloc_size - (cm->managed + m->systembits_inalloc);
-	cm->allocated = 0;
+	if (!cm->initialized) {
+		cm->available = m->alloc_size;
+		cm->available -= cm->managed + m->systembits_inalloc;
+		cm->initialized = true;
+	}
 	m->global_available += cm->available;
 	cm->online = true;
 	m->online_maps++;

@@ -370,14 +373,16 @@ void irq_matrix_free(struct irq_matrix *
 	if (WARN_ON_ONCE(bit < m->alloc_start || bit >= m->alloc_end))
 		return;
 
-	if (cm->online) {
-		clear_bit(bit, cm->alloc_map);
-		cm->allocated--;
+	clear_bit(bit, cm->alloc_map);
+	cm->allocated--;
+
+	if (cm->online)
 		m->total_allocated--;
-		if (!managed) {
-			cm->available++;
+
+	if (!managed) {
+		cm->available++;
+		if (cm->online)
 			m->global_available++;
-		}
 	}
 	trace_irq_matrix_free(bit, cpu, m, cm);
 }

Patches currently in stable-queue which might be from [email protected] are

queue-4.15/x86-oprofile-fix-bogus-gcc-8-warning-in-nmi_setup.patch queue-4.15/x86-apic-vector-handle-vector-release-on-cpu-unplug-correctly.patch queue-4.15/genirq-matrix-handle-cpu-offlining-proper.patch queue-4.15/kbuild-always-define-endianess-in-kconfig.h.patch