Commit-ID: 425a5072dcd1bd895eea90a6b495392b6358ebd0
Gitweb: http://git.kernel.org/tip/425a5072dcd1bd895eea90a6b495392b6358ebd0
Author: Thomas Gleixner <tglx@xxxxxxxxxxxxx>
AuthorDate: Sun, 13 Dec 2015 18:02:22 +0100
Committer: Thomas Gleixner <tglx@xxxxxxxxxxxxx>
CommitDate: Mon, 14 Dec 2015 10:03:46 +0100
genirq: Free irq_desc with rcu
The new VMD device driver needs to iterate over a list of
"demultiplexing" interrupts. Protecting that list with a lock is not
possible because the list is also required in code pathes which hold
irq descriptor lock. Therefor the demultiplexing interrupt handler
would create a lock inversion scenario if it calls a demux handler
with the list protection lock held.
A solution for this is to free the irq descriptor via RCU, so the
list can be walked with rcu read lock held.
Signed-off-by: Thomas Gleixner <tglx@xxxxxxxxxxxxx>
Cc: Keith Busch <keith.busch@xxxxxxxxx>
---
include/linux/irqdesc.h | 6 ++++++
kernel/irq/irqdesc.c | 19 ++++++++++++++++---
2 files changed, 22 insertions(+), 3 deletions(-)
diff --git a/include/linux/irqdesc.h b/include/linux/irqdesc.h
index a587a33..dcca77c 100644
--- a/include/linux/irqdesc.h
+++ b/include/linux/irqdesc.h
@@ -1,6 +1,8 @@
#ifndef _LINUX_IRQDESC_H
#define _LINUX_IRQDESC_H
+#include <linux/rcupdate.h>
+
/*
* Core internal functions to deal with irq descriptors
*/
@@ -40,6 +42,7 @@ struct pt_regs;
* IRQF_NO_SUSPEND set
* @force_resume_depth: number of irqactions on a irq descriptor with
* IRQF_FORCE_RESUME set
+ * @rcu: rcu head for delayed free
* @dir: /proc/irq/ procfs entry
* @name: flow handler name for /proc/interrupts output
*/
@@ -82,6 +85,9 @@ struct irq_desc {
#ifdef CONFIG_PROC_FS
struct proc_dir_entry *dir;
#endif
+#ifdef CONFIG_SPARSE_IRQ
+ struct rcu_head rcu;
+#endif
int parent_irq;
struct module *owner;
const char *name;
diff --git a/kernel/irq/irqdesc.c b/kernel/irq/irqdesc.c
index 239e2ae..0409da0 100644
--- a/kernel/irq/irqdesc.c
+++ b/kernel/irq/irqdesc.c
@@ -159,6 +159,7 @@ static struct irq_desc *alloc_desc(int irq, int node, struct module *owner)
raw_spin_lock_init(&desc->lock);
lockdep_set_class(&desc->lock, &irq_desc_lock_class);
+ init_rcu_head(&desc->rcu);
desc_set_defaults(irq, desc, node, owner);
@@ -171,6 +172,15 @@ err_desc:
return NULL;
}
+static void delayed_free_desc(struct rcu_head *rhp)
+{
+ struct irq_desc *desc = container_of(rhp, struct irq_desc, rcu);
+
+ free_masks(desc);
+ free_percpu(desc->kstat_irqs);
+ kfree(desc);
+}
+
static void free_desc(unsigned int irq)
{
struct irq_desc *desc = irq_to_desc(irq);
@@ -187,9 +197,12 @@ static void free_desc(unsigned int irq)
delete_irq_desc(irq);
mutex_unlock(&sparse_irq_lock);
- free_masks(desc);
- free_percpu(desc->kstat_irqs);
- kfree(desc);
+ /*
+ * We free the descriptor, masks and stat fields via RCU. That
+ * allows demultiplex interrupts to do rcu based management of
+ * the child interrupts.
+ */
+ call_rcu(&desc->rcu, delayed_free_desc);
}
static int alloc_descs(unsigned int start, unsigned int cnt, int node,
--
To unsubscribe from this list: send the line "unsubscribe linux-tip-commits" in
the body of a message to majordomo@xxxxxxxxxxxxxxx
More majordomo info at http://vger.kernel.org/majordomo-info.html
|