Hi Andrey, On Tue, Jan 22, 2013 at 11:15 AM, Andrey Vagin <avagin@xxxxxxxxxx> wrote: > This patch set adds ability to choose a signal queue and > to read signals without dequeuing them. > > Three new flags are added: > SFD_SHARED_QUEUE -- reads will be from process-wide shared signal queue > SFD_PER_THREAD_QUEUE -- reads will be from per-thread signal queue > SFD_PEEK -- don't dequeue signals A fuller description of the patch, including information that was in previous versions of this patch would be helpful. Let me see if I can summarize/fill out the API side of things, and ask a few questions along the way (yes, I could answer some of the questions by checking the code, but I want to know what the *intended* behavior is). The patch series adds a total of 4 flags to signalfd(). In addition to those you list above, the other is SFD_RAW -- return raw siginfo structs when reading, rather than signalfd_siginfo The intention is that these flags be used in conjunction with pread(), to peek at queued signals. The 'offset' argument is treated as a position. Thus, for example, to non-destructively read all of the per-thread signals in raw form from the per-thread queue, one would write fd = signalfd(-1, SFD_PER_THREAD_QUEUE | SFD_RAW | SFD_PEEK) for (j = 0; ; j++) { s = pread(fd, buf, ocunt, j) if (s == 0) /* No more signals */ break; } Right? Now some questions. I don't require all of the following, but I'm wanting to know what's possible, for documentation purposes. Q1: with this patch series, is it permissible to specify SFD_PER_THREAD_QUEUE or SFD_SHARED_QUEUE without specifying either SFD_PEEK or SFD_QUEUE? In other words, can one do traditional signalfd_siginfo reads, but selecting from a specific queue. Q2: Is it possible to specify SFD_PEEK without SFD_RAW, so that one can peek at siginfo structs rather than signalfd_siginfo structs? Q3: Is it possible to specify SFD_RAW without SFD_PEEK, so that one can destructively read signalfd_siginfo structs? Can that be done using any read interface (read(), pread(), etc.)? Q4: Is it possible to specify both SFD_PER_THREAD_QUEUE and SFD_SHARED_QUEUE? In that case, in what order are signals read from the two queues? Thanks, Michael > Cc: Serge Hallyn <serge.hallyn@xxxxxxxxxxxxx> > Cc: Oleg Nesterov <oleg@xxxxxxxxxx> > Cc: Andrew Morton <akpm@xxxxxxxxxxxxxxxxxxxx> > Cc: "Eric W. Biederman" <ebiederm@xxxxxxxxxxxx> > Cc: Al Viro <viro@xxxxxxxxxxxxxxxxxx> > Cc: Pavel Emelyanov <xemul@xxxxxxxxxxxxx> > CC: Cyrill Gorcunov <gorcunov@xxxxxxxxxx> > Cc: Michael Kerrisk <mtk.manpages@xxxxxxxxx> > > -- > 1.7.11.7 > -- Michael Kerrisk Linux man-pages maintainer; http://www.kernel.org/doc/man-pages/ Author of "The Linux Programming Interface"; http://man7.org/tlpi/ -- 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