Re: [PATCH v6 01/13] tools/libperf: introduce notion of static polled file descriptors

From: Adrian Hunter
Date: Wed Jun 03 2020 - 08:24:31 EST

On 3/06/20 3:01 pm, Alexey Budankov wrote:
> Hi,
> On 03.06.2020 14:38, Adrian Hunter wrote:
>> On 1/06/20 11:05 pm, Alexey Budankov wrote:
>>> Implement adding of file descriptors by fdarray__add_stat() to
>>> fix-sized (currently 1) stat_entries array located at struct fdarray.
>>> Append added file descriptors to the array used by poll() syscall
>>> during fdarray__poll() call. Copy poll() result of the added
>>> descriptors from the array back to the storage for separate analysis.
>> Why not instead call evlist__add_pollfd() before other fds are added, so
>> the fda->entries[] position is always fixed. Then this patch is not needed.
> It then will block event consumption loop, at least in record mode, due to
> change sin initial assumptions behind fdarray__filter(). So extension of the
> API with 'static' fds looks safer w.r.t. possible functional regressions at
> the same time extending the API with ability to atomically wait for (poll())
> not only event fds but also any other fds during monitoring.

So make fdarray__filter() return the number of filterable fds remaining.