The following commit has been merged in the linux branch: commit 83db93f4de2d9ae441a491d1dc61c2204f0195de Author: Neil Brown neilb@suse.de Date: Tue Sep 15 16:05:51 2009 -0700
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: Joel Andres Granados jgranado@redhat.com Signed-off-by: NeilBrown neilb@suse.de Signed-off-by: Dan Williams dan.j.williams@intel.com Cc: stable stable@kernel.org Signed-off-by: Greg Kroah-Hartman gregkh@suse.de
diff --git a/fs/sysfs/file.c b/fs/sysfs/file.c index 561a9c0..f5ea468 100644 --- a/fs/sysfs/file.c +++ b/fs/sysfs/file.c @@ -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);