Messages in this thread | | | Subject | Re: [patch/rfc] Make poll/select report error (POLLNVAL and EBADF) for unsupported files | From | Eric Dumazet <> | Date | Mon, 15 Feb 2010 18:42:39 +0100 |
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Le dimanche 14 février 2010 à 14:27 -0800, Davide Libenzi a écrit : > Currently poll and select consider a non poll-supported file as one with > full event mask set, instead of reporting proper error to the caller. > This behavior can fool the caller of proper functionality being returned, > while instead no valid event was processed/read from the device. > This came out linked to this bug report: > > http://bugzilla.kernel.org/show_bug.cgi?id=15272 > > IMHO, it'd be more adequate to report proper error code, for files that do > not support f_op->poll(), but then I am also not sure how much breakage > can this bring to existing (already broken "in just the right way") > applications. > Untested, discussion-only, patch. > > > Signed-off-by: Davide Libenzi <davidel@xmailserver.org> > > > - Davide
Hmm, according to POSIX :
The poll() function shall support regular files, terminal and pseudo-terminal devices, FIFOs, pipes, sockets ...
Regular files shall always poll TRUE for reading and writing.
So unless I missed something, this patch could break some conformant applications.
In particular, if an application is polling() on stdin (usually a tty), and other 'files', what's happening if we do :
cat replay_file | application
Either it wont read stdin, or application exits without reading its input.
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