Messages in this thread | | | Date | Wed, 5 Sep 2007 12:57:24 -0700 (PDT) | From | Davide Libenzi <> | Subject | Re: [PATCH] Revised timerfd() interface |
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On Wed, 5 Sep 2007, Michael Kerrisk wrote:
> Hi Davide, > > > > > > As I think about this more, I see more problems with > > > > > your argument. timerfd needs the ability to get and > > > > > get-while-setting just as much as the earlier APIs. > > > > > Consider a library that creates a timerfd file descriptor that > > > > > is handed off to an application: that library may want > > > > > to modify the timer settings without having to create a > > > > > new file descriptor (the app mey not be able to be told about > > > > > the new fd). Your argument just doesn't hold, AFAICS. > > > > > > > > Such hypotethical library, in case it really wanted to offer such > > > > functionality, could simply return an handle instead of the raw fd, > > > > and take care of all that stuff in userspace. > > > > > > Did I miss something? Is it not the case that as soon as the > > > library returns a handle, rather than an fd, then the whole > > > advantage of timerfd() (being able to select/poll/epoll on > > > the timer as well as other fds) is lost? > > > > Why? The handle would simply be a little struct where the timerfd fd is > > stored, and a XXX_getfd() would return it. > > So my point is, I doubt such functionalities are really needed, and I > > also argue that the kernel is the best place for such wrapper code > > to go. > > So what happens if one thread (via the library) wants modify > a timer's settings at the same timer as another thread is > select()ing on it? The first thread can't do this by creating > a new timerfd timer, since it wants to affect the select() > in the other thread?
It can be done w/out any problems. The select thread will be notified whenever the new timer setting expires.
- Davide
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