diff options
| -rw-r--r-- | fs/pipe.c | 62 | ||||
| -rw-r--r-- | fs/splice.c | 8 | ||||
| -rw-r--r-- | include/linux/pipe_fs_i.h | 5 |
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 *); |