This is a note to let you know that I've just added the patch titled
genirq/matrix: Exclude managed interrupts in irq_matrix_allocated()
to the 4.19-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-exclude-managed-interrupts-in-irq_matr.patch
and it can be found in the queue-4.19 subdirectory.
If you, or anyone else, feels it should not be added to the stable tree,
please let <stable@xxxxxxxxxxxxxxx> know about it.
commit 617ae9052115f9dd001e682599caf938281fe4f2
Author: Chen Yu <yu.c.chen@xxxxxxxxx>
Date: Fri Oct 20 15:25:22 2023 +0800
genirq/matrix: Exclude managed interrupts in irq_matrix_allocated()
[ Upstream commit a0b0bad10587ae2948a7c36ca4ffc206007fbcf3 ]
When a CPU is about to be offlined, x86 validates that all active
interrupts which are targeted to this CPU can be migrated to the remaining
online CPUs. If not, the offline operation is aborted.
The validation uses irq_matrix_allocated() to retrieve the number of
vectors which are allocated on the outgoing CPU. The returned number of
allocated vectors includes also vectors which are associated to managed
interrupts.
That's overaccounting because managed interrupts are:
- not migrated when the affinity mask of the interrupt targets only
the outgoing CPU
- migrated to another CPU, but in that case the vector is already
pre-allocated on the potential target CPUs and must not be taken into
account.
As a consequence the check whether the remaining online CPUs have enough
capacity for migrating the allocated vectors from the outgoing CPU might
fail incorrectly.
Let irq_matrix_allocated() return only the number of allocated non-managed
interrupts to make this validation check correct.
[ tglx: Amend changelog and fixup kernel-doc comment ]
Fixes: 2f75d9e1c905 ("genirq: Implement bitmap matrix allocator")
Reported-by: Wendy Wang <wendy.wang@xxxxxxxxx>
Signed-off-by: Chen Yu <yu.c.chen@xxxxxxxxx>
Signed-off-by: Thomas Gleixner <tglx@xxxxxxxxxxxxx>
Link: https://lore.kernel.org/r/20231020072522.557846-1-yu.c.chen@xxxxxxxxx
Signed-off-by: Sasha Levin <sashal@xxxxxxxxxx>
diff --git a/kernel/irq/matrix.c b/kernel/irq/matrix.c
index 8e586858bcf41..d25edbb87119f 100644
--- a/kernel/irq/matrix.c
+++ b/kernel/irq/matrix.c
@@ -466,16 +466,16 @@ unsigned int irq_matrix_reserved(struct irq_matrix *m)
}
/**
- * irq_matrix_allocated - Get the number of allocated irqs on the local cpu
+ * irq_matrix_allocated - Get the number of allocated non-managed irqs on the local CPU
* @m: Pointer to the matrix to search
*
- * This returns number of allocated irqs
+ * This returns number of allocated non-managed interrupts.
*/
unsigned int irq_matrix_allocated(struct irq_matrix *m)
{
struct cpumap *cm = this_cpu_ptr(m->maps);
- return cm->allocated;
+ return cm->allocated - cm->managed_allocated;
}
#ifdef CONFIG_GENERIC_IRQ_DEBUGFS
