Commit 83db93f4 authored by Neil Brown's avatar Neil Brown Committed by Greg Kroah-Hartman
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sysfs: Allow sysfs_notify_dirent to be called from interrupt context. 



sysfs_notify_dirent is a simple atomic operation that can be used to
alert user-space that new data can be read from a sysfs attribute.

Unfortunately it cannot currently be called from non-process context
because of its use of spin_lock which is sometimes taken with
interrupts enabled.

So change all lockers of sysfs_open_dirent_lock to disable interrupts,
thus making sysfs_notify_dirent safe to be called from non-process
context (as drivers/md does in md_safemode_timeout).

sysfs_get_open_dirent is (documented as being) only called from
process context, so it uses spin_lock_irq.  Other places
use spin_lock_irqsave.

The usage for sysfs_notify_dirent in md_safemode_timeout was
introduced in 2.6.28, so this patch is suitable for that and more
recent kernels.

Reported-by: default avatarJoel Andres Granados <jgranado@redhat.com>
Signed-off-by: default avatarNeilBrown <neilb@suse.de>
Signed-off-by: default avatarDan Williams <dan.j.williams@intel.com>
Cc: stable <stable@kernel.org>
Signed-off-by: default avatarGreg Kroah-Hartman <gregkh@suse.de>
parent a6a83577

fs/sysfs/file.c

+8 −6
Original line number Diff line number Diff line
@@ -268,7 +268,7 @@ static int sysfs_get_open_dirent(struct sysfs_dirent *sd, 
	struct sysfs_open_dirent *od, *new_od = NULL;



 retry:

	spin_lock(&sysfs_open_dirent_lock);

	spin_lock_irq(&sysfs_open_dirent_lock);



	if (!sd->s_attr.open && new_od) {

		sd->s_attr.open = new_od;
@@ -281,7 +281,7 @@ static int sysfs_get_open_dirent(struct sysfs_dirent *sd, 
		list_add_tail(&buffer->list, &od->buffers);

	}



	spin_unlock(&sysfs_open_dirent_lock);

	spin_unlock_irq(&sysfs_open_dirent_lock);



	if (od) {

		kfree(new_od);
@@ -315,8 +315,9 @@ static void sysfs_put_open_dirent(struct sysfs_dirent *sd, 
				  struct sysfs_buffer *buffer)

{

	struct sysfs_open_dirent *od = sd->s_attr.open;

	unsigned long flags;



	spin_lock(&sysfs_open_dirent_lock);

	spin_lock_irqsave(&sysfs_open_dirent_lock, flags);



	list_del(&buffer->list);

	if (atomic_dec_and_test(&od->refcnt))
@@ -324,7 +325,7 @@ static void sysfs_put_open_dirent(struct sysfs_dirent *sd, 
	else

		od = NULL;



	spin_unlock(&sysfs_open_dirent_lock);

	spin_unlock_irqrestore(&sysfs_open_dirent_lock, flags);



	kfree(od);

}
@@ -456,8 +457,9 @@ static unsigned int sysfs_poll(struct file *filp, poll_table *wait) 
void sysfs_notify_dirent(struct sysfs_dirent *sd)

{

	struct sysfs_open_dirent *od;

	unsigned long flags;



	spin_lock(&sysfs_open_dirent_lock);

	spin_lock_irqsave(&sysfs_open_dirent_lock, flags);



	od = sd->s_attr.open;

	if (od) {
@@ -465,7 +467,7 @@ void sysfs_notify_dirent(struct sysfs_dirent *sd) 
		wake_up_interruptible(&od->poll);

	}



	spin_unlock(&sysfs_open_dirent_lock);

	spin_unlock_irqrestore(&sysfs_open_dirent_lock, flags);

}

EXPORT_SYMBOL_GPL(sysfs_notify_dirent);

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