Fix a lockdep warning in fasync_helper()
Lockdep gripes if file->f_lock is taken in a no-IRQ situation, since that
is not always the case. We don't really want to disable IRQs for every
acquisition of f_lock; instead, just move it outside of fasync_lock.
Reported-by: Bartlomiej Zolnierkiewicz <bzolnier@gmail.com>
Reported-by: Larry Finger <Larry.Finger@lwfinger.net>
Reported-by: Wu Fengguang <fengguang.wu@intel.com>
Signed-off-by: Jonathan Corbet <corbet@lwn.net>
diff --git a/fs/fcntl.c b/fs/fcntl.c
index d865ca66..cc8e4de 100644
--- a/fs/fcntl.c
+++ b/fs/fcntl.c
@@ -531,6 +531,12 @@
if (!new)
return -ENOMEM;
}
+
+ /*
+ * We need to take f_lock first since it's not an IRQ-safe
+ * lock.
+ */
+ spin_lock(&filp->f_lock);
write_lock_irq(&fasync_lock);
for (fp = fapp; (fa = *fp) != NULL; fp = &fa->fa_next) {
if (fa->fa_file == filp) {
@@ -555,14 +561,12 @@
result = 1;
}
out:
- /* Fix up FASYNC bit while still holding fasync_lock */
- spin_lock(&filp->f_lock);
if (on)
filp->f_flags |= FASYNC;
else
filp->f_flags &= ~FASYNC;
- spin_unlock(&filp->f_lock);
write_unlock_irq(&fasync_lock);
+ spin_unlock(&filp->f_lock);
return result;
}
diff --git a/include/linux/fs.h b/include/linux/fs.h
index 7428c6d..2f13c1d 100644
--- a/include/linux/fs.h
+++ b/include/linux/fs.h
@@ -848,7 +848,7 @@
#define f_dentry f_path.dentry
#define f_vfsmnt f_path.mnt
const struct file_operations *f_op;
- spinlock_t f_lock; /* f_ep_links, f_flags */
+ spinlock_t f_lock; /* f_ep_links, f_flags, no IRQ */
atomic_long_t f_count;
unsigned int f_flags;
fmode_t f_mode;