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Subject[PATCH 4.15 16/64] genirq/matrix: Handle CPU offlining proper
Date
4.15-stable review patch.  If anyone has any objections, please let me know.

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

From: Thomas Gleixner <tglx@linutronix.de>

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.

Fixes: 2f75d9e1c905 ("genirq: Implement bitmap matrix allocator")
Reported-by: Yuriy Vostrikov <delamonpansie@gmail.com>
Signed-off-by: Thomas Gleixner <tglx@linutronix.de>
Tested-by: Yuriy Vostrikov <delamonpansie@gmail.com>
Cc: Peter Zijlstra <peterz@infradead.org>
Cc: Randy Dunlap <rdunlap@infradead.org>
Cc: stable@vger.kernel.org
Link: https://lkml.kernel.org/r/20180222112316.849980972@linutronix.de
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>

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

--- a/kernel/irq/matrix.c
+++ b/kernel/irq/matrix.c
@@ -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);
}

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