On 03/11, Hillf Danton wrote: > > On Mon, 10 Mar 2025 13:43:42 +0100 Oleg Nesterov > > > > Hmm. I don't understand you, again. > > > > OK, once some writer writes at least one byte (this will make the > > pipe_empty() condition false) and wakes this reader up. > > > > If you meant something else, say, if you referred to you previous > > scenario, please clarify your question. > > > The step-03 in my scenario [1] shows a reader sleeps at line-370 after > making the pipe empty, so after your change that cuts the chance for > waking up writer, We are circling. Once again, in this case "wake_writer" can't be true when the reader does wait_event(rd_wait), this code can be replaced with BUG_ON(wake_writer). So that change cuts nothing. It simply has no effect in this case. > who will wake up the sleeping reader? Nobody. > > Feel free to check my scenario again. > > step-03 > task-118766 new reader > makes pipe empty > sleeps > > [1] https://lore.kernel.org/lkml/20250307060827.3083-1-hdanton@xxxxxxxx/ First of all, task-118766 won't sleep unless it calls read() again.
