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Subject[PATCH] irq/irq_sim: store multiple interrupt offsets in a bitmap
Date
Two threads can try to fire the irq_sim with different offsets and will
end up fighting for the irq_work asignment. Thomas Gleixner suggested a
solution based on a bitfield where we set a bit for every offset
associated with an interrupt that should be fired and then iterate over
all set bits in the interrupt handler.

This is a slightly modified solution using a bitmap so that we don't
impose a limit on the number of interrupts one can allocate with
irq_sim.

Suggested-by: Thomas Gleixner <tglx@linutronix.de>
Signed-off-by: Bartosz Golaszewski <brgl@bgdev.pl>
---
include/linux/irq_sim.h | 2 +-
kernel/irq/irq_sim.c | 23 +++++++++++++++++++++--
2 files changed, 22 insertions(+), 3 deletions(-)

diff --git a/include/linux/irq_sim.h b/include/linux/irq_sim.h
index 630a57e55db6..4500d453a63e 100644
--- a/include/linux/irq_sim.h
+++ b/include/linux/irq_sim.h
@@ -16,7 +16,7 @@

struct irq_sim_work_ctx {
struct irq_work work;
- int irq;
+ unsigned long *pending;
};

struct irq_sim_irq_ctx {
diff --git a/kernel/irq/irq_sim.c b/kernel/irq/irq_sim.c
index dd20d0d528d4..98a20e1594ce 100644
--- a/kernel/irq/irq_sim.c
+++ b/kernel/irq/irq_sim.c
@@ -34,9 +34,20 @@ static struct irq_chip irq_sim_irqchip = {
static void irq_sim_handle_irq(struct irq_work *work)
{
struct irq_sim_work_ctx *work_ctx;
+ unsigned int offset = 0;
+ struct irq_sim *sim;
+ int irqnum;

work_ctx = container_of(work, struct irq_sim_work_ctx, work);
- handle_simple_irq(irq_to_desc(work_ctx->irq));
+ sim = container_of(work_ctx, struct irq_sim, work_ctx);
+
+ while (!bitmap_empty(work_ctx->pending, sim->irq_count)) {
+ offset = find_next_bit(work_ctx->pending,
+ sim->irq_count, offset);
+ clear_bit(offset, work_ctx->pending);
+ irqnum = irq_sim_irqnum(sim, offset);
+ handle_simple_irq(irq_to_desc(irqnum));
+ }
}

/**
@@ -63,6 +74,13 @@ int irq_sim_init(struct irq_sim *sim, unsigned int num_irqs)
return sim->irq_base;
}

+ sim->work_ctx.pending = bitmap_zalloc(num_irqs, GFP_KERNEL);
+ if (!sim->work_ctx.pending) {
+ kfree(sim->irqs);
+ irq_free_descs(sim->irq_base, num_irqs);
+ return -ENOMEM;
+ }
+
for (i = 0; i < num_irqs; i++) {
sim->irqs[i].irqnum = sim->irq_base + i;
sim->irqs[i].enabled = false;
@@ -89,6 +107,7 @@ EXPORT_SYMBOL_GPL(irq_sim_init);
void irq_sim_fini(struct irq_sim *sim)
{
irq_work_sync(&sim->work_ctx.work);
+ bitmap_free(sim->work_ctx.pending);
irq_free_descs(sim->irq_base, sim->irq_count);
kfree(sim->irqs);
}
@@ -143,7 +162,7 @@ EXPORT_SYMBOL_GPL(devm_irq_sim_init);
void irq_sim_fire(struct irq_sim *sim, unsigned int offset)
{
if (sim->irqs[offset].enabled) {
- sim->work_ctx.irq = irq_sim_irqnum(sim, offset);
+ set_bit(offset, sim->work_ctx.pending);
irq_work_queue(&sim->work_ctx.work);
}
}
--
2.19.1
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