提交 425a5072 编写于 作者: T Thomas Gleixner

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: NThomas Gleixner <tglx@linutronix.de>
Cc: Keith Busch <keith.busch@intel.com>
上级 f0cb3220
#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
*/
......@@ -81,6 +84,9 @@ struct irq_desc {
#endif
#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;
......
......@@ -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 @@ static struct irq_desc *alloc_desc(int irq, int node, struct module *owner)
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,
......
Markdown is supported
0% .
You are about to add 0 people to the discussion. Proceed with caution.
先完成此消息的编辑!
想要评论请 注册