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Commit ac88ee3b authored by Linus Torvalds's avatar Linus Torvalds
Browse files

Merge branch 'irq-urgent-for-linus' of git://git.kernel.org/pub/scm/linux/kernel/git/tip/tip 

Pull irq core fix from Thomas Gleixner:
 "A single fix plugging a long standing race between proc/stat and
  proc/interrupts access and freeing of interrupt descriptors"

* 'irq-urgent-for-linus' of git://git.kernel.org/pub/scm/linux/kernel/git/tip/tip:
  genirq: Prevent proc race against freeing of irq descriptors
parents a5445576 c291ee62

fs/proc/stat.c

+1 −1
Original line number Diff line number Diff line
@@ -159,7 +159,7 @@ static int show_stat(struct seq_file *p, void *v) 


	/* sum again ? it could be updated? */

	for_each_irq_nr(j)

		seq_put_decimal_ull(p, ' ', kstat_irqs(j));

		seq_put_decimal_ull(p, ' ', kstat_irqs_usr(j));



	seq_printf(p,

		"\nctxt %llu\n"

include/linux/kernel_stat.h

+1 −0
Original line number Diff line number Diff line
@@ -68,6 +68,7 @@ static inline unsigned int kstat_softirqs_cpu(unsigned int irq, int cpu) 
 * Number of interrupts per specific IRQ source, since bootup

 */

extern unsigned int kstat_irqs(unsigned int irq);

extern unsigned int kstat_irqs_usr(unsigned int irq);



/*

 * Number of interrupts per cpu, since bootup

kernel/irq/internals.h

+4 −0
Original line number Diff line number Diff line
@@ -78,8 +78,12 @@ extern void unmask_threaded_irq(struct irq_desc *desc); 


#ifdef CONFIG_SPARSE_IRQ

static inline void irq_mark_irq(unsigned int irq) { }

extern void irq_lock_sparse(void);

extern void irq_unlock_sparse(void);

#else

extern void irq_mark_irq(unsigned int irq);

static inline void irq_lock_sparse(void) { }

static inline void irq_unlock_sparse(void) { }

#endif



extern void init_kstat_irqs(struct irq_desc *desc, int node, int nr);

kernel/irq/irqdesc.c

+52 −0
Original line number Diff line number Diff line
@@ -132,6 +132,16 @@ static void free_masks(struct irq_desc *desc) 
static inline void free_masks(struct irq_desc *desc) { }

#endif



void irq_lock_sparse(void)

{

	mutex_lock(&sparse_irq_lock);

}



void irq_unlock_sparse(void)

{

	mutex_unlock(&sparse_irq_lock);

}



static struct irq_desc *alloc_desc(int irq, int node, struct module *owner)

{

	struct irq_desc *desc;
@@ -168,6 +178,12 @@ static void free_desc(unsigned int irq) 


	unregister_irq_proc(irq, desc);



	/*

	 * sparse_irq_lock protects also show_interrupts() and

	 * kstat_irq_usr(). Once we deleted the descriptor from the

	 * sparse tree we can free it. Access in proc will fail to

	 * lookup the descriptor.

	 */

	mutex_lock(&sparse_irq_lock);

	delete_irq_desc(irq);

	mutex_unlock(&sparse_irq_lock);
@@ -574,6 +590,15 @@ void kstat_incr_irq_this_cpu(unsigned int irq) 
	kstat_incr_irqs_this_cpu(irq, irq_to_desc(irq));

}



/**

 * kstat_irqs_cpu - Get the statistics for an interrupt on a cpu

 * @irq:	The interrupt number

 * @cpu:	The cpu number

 *

 * Returns the sum of interrupt counts on @cpu since boot for

 * @irq. The caller must ensure that the interrupt is not removed

 * concurrently.

 */

unsigned int kstat_irqs_cpu(unsigned int irq, int cpu)

{

	struct irq_desc *desc = irq_to_desc(irq);
@@ -582,6 +607,14 @@ unsigned int kstat_irqs_cpu(unsigned int irq, int cpu) 
			*per_cpu_ptr(desc->kstat_irqs, cpu) : 0;

}



/**

 * kstat_irqs - Get the statistics for an interrupt

 * @irq:	The interrupt number

 *

 * Returns the sum of interrupt counts on all cpus since boot for

 * @irq. The caller must ensure that the interrupt is not removed

 * concurrently.

 */

unsigned int kstat_irqs(unsigned int irq)

{

	struct irq_desc *desc = irq_to_desc(irq);
@@ -594,3 +627,22 @@ unsigned int kstat_irqs(unsigned int irq) 
		sum += *per_cpu_ptr(desc->kstat_irqs, cpu);

	return sum;

}



/**

 * kstat_irqs_usr - Get the statistics for an interrupt

 * @irq:	The interrupt number

 *

 * Returns the sum of interrupt counts on all cpus since boot for

 * @irq. Contrary to kstat_irqs() this can be called from any

 * preemptible context. It's protected against concurrent removal of

 * an interrupt descriptor when sparse irqs are enabled.

 */

unsigned int kstat_irqs_usr(unsigned int irq)

{

	int sum;



	irq_lock_sparse();

	sum = kstat_irqs(irq);

	irq_unlock_sparse();

	return sum;

}

kernel/irq/proc.c

+21 −1
Original line number Diff line number Diff line
@@ -15,6 +15,23 @@ 


#include "internals.h"



/*

 * Access rules:

 *

 * procfs protects read/write of /proc/irq/N/ files against a

 * concurrent free of the interrupt descriptor. remove_proc_entry()

 * immediately prevents new read/writes to happen and waits for

 * already running read/write functions to complete.

 *

 * We remove the proc entries first and then delete the interrupt

 * descriptor from the radix tree and free it. So it is guaranteed

 * that irq_to_desc(N) is valid as long as the read/writes are

 * permitted by procfs.

 *

 * The read from /proc/interrupts is a different problem because there

 * is no protection. So the lookup and the access to irqdesc

 * information must be protected by sparse_irq_lock.

 */

static struct proc_dir_entry *root_irq_dir;



#ifdef CONFIG_SMP
@@ -437,9 +454,10 @@ int show_interrupts(struct seq_file *p, void *v) 
		seq_putc(p, '\n');

	}



	irq_lock_sparse();

	desc = irq_to_desc(i);

	if (!desc)

		return 0;

		goto outsparse;



	raw_spin_lock_irqsave(&desc->lock, flags);

	for_each_online_cpu(j)
@@ -479,6 +497,8 @@ int show_interrupts(struct seq_file *p, void *v) 
	seq_putc(p, '\n');

out:

	raw_spin_unlock_irqrestore(&desc->lock, flags);

outsparse:

	irq_unlock_sparse();

	return 0;

}

#endif