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Diffstat (limited to 'fs/pipe.c')
-rw-r--r--fs/pipe.c73
1 files changed, 46 insertions, 27 deletions
diff --git a/fs/pipe.c b/fs/pipe.c
index 60dbee457143..0ac197658a2d 100644
--- a/fs/pipe.c
+++ b/fs/pipe.c
@@ -106,25 +106,6 @@ void pipe_double_lock(struct pipe_inode_info *pipe1,
}
}
-/* Drop the inode semaphore and wait for a pipe event, atomically */
-void pipe_wait(struct pipe_inode_info *pipe)
-{
- DEFINE_WAIT(rdwait);
- DEFINE_WAIT(wrwait);
-
- /*
- * Pipes are system-local resources, so sleeping on them
- * is considered a noninteractive wait:
- */
- prepare_to_wait(&pipe->rd_wait, &rdwait, TASK_INTERRUPTIBLE);
- prepare_to_wait(&pipe->wr_wait, &wrwait, TASK_INTERRUPTIBLE);
- pipe_unlock(pipe);
- schedule();
- finish_wait(&pipe->rd_wait, &rdwait);
- finish_wait(&pipe->wr_wait, &wrwait);
- pipe_lock(pipe);
-}
-
static void anon_pipe_buf_release(struct pipe_inode_info *pipe,
struct pipe_buffer *buf)
{
@@ -913,19 +894,18 @@ int create_pipe_files(struct file **res, int flags)
{
struct inode *inode = get_pipe_inode();
struct file *f;
+ int error;
if (!inode)
return -ENFILE;
if (flags & O_NOTIFICATION_PIPE) {
-#ifdef CONFIG_WATCH_QUEUE
- if (watch_queue_init(inode->i_pipe) < 0) {
+ error = watch_queue_init(inode->i_pipe);
+ if (error) {
+ free_pipe_info(inode->i_pipe);
iput(inode);
- return -ENOMEM;
+ return error;
}
-#else
- return -ENOPKG;
-#endif
}
f = alloc_file_pseudo(inode, pipe_mnt, "",
@@ -1035,12 +1015,52 @@ SYSCALL_DEFINE1(pipe, int __user *, fildes)
return do_pipe2(fildes, 0);
}
+/*
+ * This is the stupid "wait for pipe to be readable or writable"
+ * model.
+ *
+ * See pipe_read/write() for the proper kind of exclusive wait,
+ * but that requires that we wake up any other readers/writers
+ * if we then do not end up reading everything (ie the whole
+ * "wake_next_reader/writer" logic in pipe_read/write()).
+ */
+void pipe_wait_readable(struct pipe_inode_info *pipe)
+{
+ pipe_unlock(pipe);
+ wait_event_interruptible(pipe->rd_wait, pipe_readable(pipe));
+ pipe_lock(pipe);
+}
+
+void pipe_wait_writable(struct pipe_inode_info *pipe)
+{
+ pipe_unlock(pipe);
+ wait_event_interruptible(pipe->wr_wait, pipe_writable(pipe));
+ pipe_lock(pipe);
+}
+
+/*
+ * This depends on both the wait (here) and the wakeup (wake_up_partner)
+ * holding the pipe lock, so "*cnt" is stable and we know a wakeup cannot
+ * race with the count check and waitqueue prep.
+ *
+ * Normally in order to avoid races, you'd do the prepare_to_wait() first,
+ * then check the condition you're waiting for, and only then sleep. But
+ * because of the pipe lock, we can check the condition before being on
+ * the wait queue.
+ *
+ * We use the 'rd_wait' waitqueue for pipe partner waiting.
+ */
static int wait_for_partner(struct pipe_inode_info *pipe, unsigned int *cnt)
{
+ DEFINE_WAIT(rdwait);
int cur = *cnt;
while (cur == *cnt) {
- pipe_wait(pipe);
+ prepare_to_wait(&pipe->rd_wait, &rdwait, TASK_INTERRUPTIBLE);
+ pipe_unlock(pipe);
+ schedule();
+ finish_wait(&pipe->rd_wait, &rdwait);
+ pipe_lock(pipe);
if (signal_pending(current))
break;
}
@@ -1050,7 +1070,6 @@ static int wait_for_partner(struct pipe_inode_info *pipe, unsigned int *cnt)
static void wake_up_partner(struct pipe_inode_info *pipe)
{
wake_up_interruptible_all(&pipe->rd_wait);
- wake_up_interruptible_all(&pipe->wr_wait);
}
static int fifo_open(struct inode *inode, struct file *filp)