Messages in this thread |  | | Date | Tue, 25 Feb 2014 10:30:14 +0000 | From | Eric Wong <> | Subject | Re: [RFC PATCH for-next 2/4] epoll: epoll() syscall declaration |
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Nathaniel Yazdani <n1ght.4nd.d4y@gmail.com> wrote: > On Sun, Feb 23, 2014 at 9:32 PM, Eric Wong <normalperson@yhbt.net> wrote: > > Nathaniel Yazdani <n1ght.4nd.d4y@gmail.com> wrote: > >> +asmlinkage long sys_epoll(int ep, struct epoll __user *in, > >> + unsigned int inc, struct epoll __user *out, > >> + unsigned int outc, int timeout); > > > > I can understand using the new struct for 'in', but 'out' could just be > > "struct epoll_event *" like sys_epoll_wait, right? > > > >> asmlinkage long sys_epoll_wait(int epfd, struct epoll_event __user *events, > > Yeah and I went back and forth on that, it just seemed to me that the > inconsistency could be confusing to others... maybe instead of defining a new > struct to begin with it might make me sense to just have an 'infd' array of file > descriptors in addition to an 'in' array of epoll_event struct > (obviously the length > of these would be identical).
I don't think a separate array for in is a good idea, too error prone and you lose locality.
For output, some users either end up allocating more memory/retrieve fewer items with the larger struct for *out.
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