On Fri, Sep 05, 2014 at 11:07:56AM -0300, Arnaldo Carvalho de Melo wrote: > Em Fri, Sep 05, 2014 at 11:42:59AM +0300, Adrian Hunter escreveu: > > On 09/04/2014 06:19 PM, Arnaldo Carvalho de Melo wrote: > > > Em Thu, Sep 04, 2014 at 03:32:08PM +0300, Adrian Hunter escreveu: > > No I was meaning something different. For example, 'perf record' opens an > > event for 2 processes per-cpu and gets 4 file descriptors: > > > task1 task2 > > cpu0 fd0 fd1 > > cpu1 fd2 fd3 > > > Now, perf record will mmap fd0 and fd2 and set-output fd1->fd0 > > and fd3->fd2. > > > pollfds includes only fd0 and fd2. > > > But if task2 exits, the POLLHUP will appear on fd1 and fd3. > > So? We are not interested in fd1 and fd3, since all our reading is done > on fd0 and fd2 mmaps, no?
hm, what if task1 (fd0, fd2) exits first.. perf record will exit, but it still has to read task2..? > > I.e. when we ask the kernel to point fd B to fd A's mmap (what you > called set-output) and fd B inserts an event into fd A's mmap ring > buffer, we get fd A poll return as POLLRD, no? > > Have to check... Otherwise we would have to poll all fds all the time, > not just the ones mmaping, right? > > > I think Jiri's patchset changed pollfds to include all fds for that reason. hm, I did not think of that.. ;-) I needed more grained feedback for future features like cpu hotplug > > It did? I have to look again, probably went together with other changes, > has it? it was done by replacing 'int' with 'struct poll_item' for evsel::fd xyarray jirka -- To unsubscribe from this list: send the line "unsubscribe linux-kernel" in the body of a message to [email protected] More majordomo info at http://vger.kernel.org/majordomo-info.html Please read the FAQ at http://www.tux.org/lkml/
