From 4a6a4499693a419a20559c41e33a7bd70bf20a6f Mon Sep 17 00:00:00 2001
From: Jonathan Corbet <corbet@lwn.net>
Date: Fri, 27 Mar 2009 12:24:31 -0600
Subject: 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>
---
fs/fcntl.c | 10 +++++++---
1 file changed, 7 insertions(+), 3 deletions(-)
(limited to 'fs/fcntl.c')
diff --git a/fs/fcntl.c b/fs/fcntl.c
index d865ca66ccb..cc8e4de2fee 100644
--- a/fs/fcntl.c
+++ b/fs/fcntl.c
@@ -531,6 +531,12 @@ int fasync_helper(int fd, struct file * filp, int on, struct fasync_struct **fap
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 @@ int fasync_helper(int fd, struct file * filp, int on, struct fasync_struct **fap
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;
}
--
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