Hmm... Suppose that pipe is full, a writer W tries to write a single byte and sleeps on pipe->wr_wait. A reader reads PAGE_SIZE bytes, updates pipe->tail, and wakes W up. But, before the woken W takes pipe->mutex, another writer comes and writes 1 byte. This updates ->head and makes pipe_full() true again. Now, W could happily merge its "small" write into the last buffer, but it will sleep again, despite the fact the last buffer has room for 4095 bytes. Sapkal, I don't think this can explain the hang, receiver()->read() should wake this writer later anyway. But could you please retest with the patch below? Thanks, Oleg. --- diff --git a/fs/pipe.c b/fs/pipe.c index b0641f75b1ba..222881559c30 100644 --- a/fs/pipe.c +++ b/fs/pipe.c @@ -455,6 +455,7 @@ anon_pipe_write(struct kiocb *iocb, struct iov_iter *from) * page-aligns the rest of the writes for large writes * spanning multiple pages. */ +again: head = pipe->head; was_empty = pipe_empty(head, pipe->tail); chars = total_len & (PAGE_SIZE-1); @@ -559,8 +560,8 @@ anon_pipe_write(struct kiocb *iocb, struct iov_iter *from) kill_fasync(&pipe->fasync_readers, SIGIO, POLL_IN); wait_event_interruptible_exclusive(pipe->wr_wait, pipe_writable(pipe)); mutex_lock(&pipe->mutex); - was_empty = pipe_empty(pipe->head, pipe->tail); wake_next_writer = true; + goto again; } out: if (pipe_full(pipe->head, pipe->tail, pipe->max_usage))
