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Fix a lockdep warning in fasync_helper()

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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>
This commit is contained in:
Jonathan Corbet 2009-03-27 12:24:31 -06:00
parent 996ff68d8b
commit 4a6a449969
2 changed files with 8 additions and 4 deletions
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10
fs/fcntl.c
View File

@ -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;
}

2
include/linux/fs.h
View File

@ -848,7 +848,7 @@ struct file {
#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;