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Subject[patch 4/5] genirq: Move irq resource handling out of spinlocked region
Aside of being conceptually wrong, there is also an actual (hard to
trigger and mostly theoretical) problem.

CPU0 CPU1
free_irq(X) interrupt X
spin_lock(desc->lock)
wake irq thread()
spin_unlock(desc->lock)
spin_lock(desc->lock)
remove action()
shutdown_irq()
release_resources() thread_handler()
spin_unlock(desc->lock) access released resources.

synchronize_irq()

Move the release resources invocation after synchronize_irq() so it's
guaranteed that the threaded handler has finished.

Move the resource request call out of the desc->lock held region as well,
so the invocation context is the same for both request and release.

This solves the problems with those functions on RT as well.

Signed-off-by: Thomas Gleixner <tglx@linutronix.de>
---
kernel/irq/manage.c | 23 +++++++++++++++--------
1 file changed, 15 insertions(+), 8 deletions(-)

--- a/kernel/irq/manage.c
+++ b/kernel/irq/manage.c
@@ -1168,6 +1168,14 @@ static int
new->flags &= ~IRQF_ONESHOT;

mutex_lock(&desc->request_mutex);
+ if (!desc->action) {
+ ret = irq_request_resources(desc);
+ if (ret) {
+ pr_err("Failed to request resources for %s (irq %d) on irqchip %s\n",
+ new->name, irq, desc->irq_data.chip->name);
+ goto out_mutex;
+ }
+ }

chip_bus_lock(desc);

@@ -1271,13 +1279,6 @@ static int
}

if (!shared) {
- ret = irq_request_resources(desc);
- if (ret) {
- pr_err("Failed to request resources for %s (irq %d) on irqchip %s\n",
- new->name, irq, desc->irq_data.chip->name);
- goto out_unlock;
- }
-
init_waitqueue_head(&desc->wait_for_threads);

/* Setup the type (level, edge polarity) if configured: */
@@ -1386,6 +1387,10 @@ static int

chip_bus_sync_unlock(desc);

+ if (!desc->action)
+ irq_release_resources(desc);
+
+out_mutex:
mutex_unlock(&desc->request_mutex);

out_thread:
@@ -1484,7 +1489,6 @@ static struct irqaction *__free_irq(unsi
if (!desc->action) {
irq_settings_clr_disable_unlazy(desc);
irq_shutdown(desc);
- irq_release_resources(desc);
irq_remove_timings(desc);
}

@@ -1527,6 +1531,9 @@ static struct irqaction *__free_irq(unsi
}
}

+ if (!desc->action)
+ irq_release_resources(desc);
+
mutex_unlock(&desc->request_mutex);

irq_chip_pm_put(&desc->irq_data);

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