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-rw-r--r--fs/pipe.c62
-rw-r--r--fs/splice.c8
-rw-r--r--include/linux/pipe_fs_i.h5
3 files changed, 48 insertions, 27 deletions
diff --git a/fs/pipe.c b/fs/pipe.c
index 60dbee457143..117db82b10af 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)
{
@@ -1035,12 +1016,52 @@ 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 +1071,6 @@ 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)
diff --git a/fs/splice.c b/fs/splice.c
index d7c8a7c4db07..c3d00dfc7344 100644
--- a/fs/splice.c
+++ b/fs/splice.c
@@ -563,7 +563,7 @@ static int splice_from_pipe_next(struct pipe_inode_info *pipe, struct splice_des
sd->need_wakeup = false;
}
- pipe_wait(pipe);
+ pipe_wait_readable(pipe);
}
return 1;
@@ -1077,7 +1077,7 @@ static int wait_for_space(struct pipe_inode_info *pipe, unsigned flags)
return -EAGAIN;
if (signal_pending(current))
return -ERESTARTSYS;
- pipe_wait(pipe);
+ pipe_wait_writable(pipe);
}
}
@@ -1454,7 +1454,7 @@ static int ipipe_prep(struct pipe_inode_info *pipe, unsigned int flags)
ret = -EAGAIN;
break;
}
- pipe_wait(pipe);
+ pipe_wait_readable(pipe);
}
pipe_unlock(pipe);
@@ -1493,7 +1493,7 @@ static int opipe_prep(struct pipe_inode_info *pipe, unsigned int flags)
ret = -ERESTARTSYS;
break;
}
- pipe_wait(pipe);
+ pipe_wait_writable(pipe);
}
pipe_unlock(pipe);
diff --git a/include/linux/pipe_fs_i.h b/include/linux/pipe_fs_i.h
index 50afd0d0084c..5d2705f1d01c 100644
--- a/include/linux/pipe_fs_i.h
+++ b/include/linux/pipe_fs_i.h
@@ -240,8 +240,9 @@ extern unsigned int pipe_max_size;
extern unsigned long pipe_user_pages_hard;
extern unsigned long pipe_user_pages_soft;
-/* Drop the inode semaphore and wait for a pipe event, atomically */
-void pipe_wait(struct pipe_inode_info *pipe);
+/* Wait for a pipe to be readable/writable while dropping the pipe lock */
+void pipe_wait_readable(struct pipe_inode_info *);
+void pipe_wait_writable(struct pipe_inode_info *);
struct pipe_inode_info *alloc_pipe_info(void);
void free_pipe_info(struct pipe_inode_info *);