Lukas Czerner <lczerner@xxxxxxxxxx> writes: > On Fri, 4 Mar 2011, Jeff Moyer wrote: >> It seems to me like it might be better to just not complete anything >> until the count is zero. Why issue a wakeup for every bio? >> fs/direct-io does something similar, maybe take a look at the >> dio_bio_end* routines and see if that would fit well here. With your >> scheme, I worry about missing a completion, maybe because the first bio >> completes before you are done submitting bios. Is that possible? > > I do not think it is possible. For every bio submitted there is > wait_for_completion called. When bio complete()s completion->done is > incremented (under the wait->lock). In wait_for_completion() we are > waiting for single submitted bio to complete (completion->done > 0), > then completion->done is decremented. It seems like simple > synchronization. > > I am not sure what wakeup you have in mind, but thanks for the tip I'll > look in fs/direct-io. Let's say you have several bios to submit, and the first bio is errored immediately in submit_bio. Since you didn't add yourself to the waitqueue yet, you might miss the wakeup and sleep forever. Cheers, Jeff -- To unsubscribe from this list: send the line "unsubscribe linux-fsdevel" in the body of a message to majordomo@xxxxxxxxxxxxxxx More majordomo info at http://vger.kernel.org/majordomo-info.html
