diff options
| author | Jens Axboe <axboe@suse.de> | 2006-04-19 15:56:40 +0200 |
|---|---|---|
| committer | Jens Axboe <axboe@suse.de> | 2006-04-19 15:56:40 +0200 |
| commit | 2a27250e6cf47ca1ea3bea0a55e4b7889c097627 (patch) | |
| tree | 3dbd4747df21e72420ab6fb91fc174173903c803 /fs/splice.c | |
| parent | c4f895cbe1e95aab633207fb19c650b7c984c01a (diff) | |
[PATCH] tee: link_pipe() must be careful when dropping one of the pipe locks
We need to ensure that we only drop a lock that is ordered last, to avoid
ABBA deadlocks with competing processes.
Signed-off-by: Jens Axboe <axboe@suse.de>
Diffstat (limited to 'fs/splice.c')
| -rw-r--r-- | fs/splice.c | 18 |
1 files changed, 14 insertions, 4 deletions
diff --git a/fs/splice.c b/fs/splice.c index 78cd264340f..4f5e6b09fb2 100644 --- a/fs/splice.c +++ b/fs/splice.c @@ -1012,7 +1012,9 @@ static int link_pipe(struct pipe_inode_info *ipipe, size_t len, unsigned int flags) { struct pipe_buffer *ibuf, *obuf; - int ret = 0, do_wakeup = 0, i; + int ret, do_wakeup, i, ipipe_first; + + ret = do_wakeup = ipipe_first = 0; /* * Potential ABBA deadlock, work around it by ordering lock @@ -1020,6 +1022,7 @@ static int link_pipe(struct pipe_inode_info *ipipe, * could deadlock (one doing tee from A -> B, the other from B -> A). */ if (ipipe->inode < opipe->inode) { + ipipe_first = 1; mutex_lock(&ipipe->inode->i_mutex); mutex_lock(&opipe->inode->i_mutex); } else { @@ -1068,9 +1071,11 @@ static int link_pipe(struct pipe_inode_info *ipipe, /* * We have input available, but no output room. - * If we already copied data, return that. + * If we already copied data, return that. If we + * need to drop the opipe lock, it must be ordered + * last to avoid deadlocks. */ - if (flags & SPLICE_F_NONBLOCK) { + if ((flags & SPLICE_F_NONBLOCK) || !ipipe_first) { if (!ret) ret = -EAGAIN; break; @@ -1104,7 +1109,12 @@ static int link_pipe(struct pipe_inode_info *ipipe, if (ret) break; } - if (flags & SPLICE_F_NONBLOCK) { + /* + * pipe_wait() drops the ipipe mutex. To avoid deadlocks + * with another process, we can only safely do that if + * the ipipe lock is ordered last. + */ + if ((flags & SPLICE_F_NONBLOCK) || ipipe_first) { if (!ret) ret = -EAGAIN; break; |