Date: Tue, 1 Mar 2016 17:34:19 -0500 From: Rich Felker <dalias@...c.org> To: musl@...ts.openwall.com Subject: Re: [PATCH] add sched_getcpu On Tue, Mar 01, 2016 at 09:35:21PM +0100, Tomasz Sterna wrote: > W dniu 29.02.2016, pon o godzinie 16∶30 -0500, użytkownik Rich Felker > napisał: > > There are a lot of Linux specific syscalls without libc wrappers. > > > Is this one special enough? > > I wouldn't say there are a lot; do you have a list? > > $ grep -roh 'syscall(SYS_[a-z]*' src/kits/kernel/ | sort -u > syscall(SYS_exit SYS_exit cannot be used safely unless you have a single-threaded program, and in that case you can use _exit (SYS_exit_group). > syscall(SYS_futex There's work on getting glibc to expose futex, but I want to ensure that we do it in a compatible (in terms of types used, and where the declaration and macros get defined) way, so I'm waiting til we reach consensus on that to take any action in musl. > syscall(SYS_gettid For glibc it's been controversial whether to expose tids as a public API, since it pokes through the pthread abstraction and imposes a 1:1 threads implementation. My view is that, unless you want to write a gigantic framework emulating each blocking syscall in userspace, POSIX already imposes a 1:1 threads implementation, and it's stupid to still pretend that M:N is viable. > syscall(SYS_tgkill tgkill also requires tids to be exposed an potentially has other issues, and doesn't seem to offer anything that pthread_kill doesn't. > > The topic of what should and should not be given libc wrappers has > > been under discussion on the glibc list for a while now. [...] > > You should not need to use syscall() to access any Linux > > functionality that's meant to be exposed to applications; [...] > > Really depends on how you define "applications". I mean syscalls that are intended for writing application programs rather than for implementing the userspace part of C/POSIX. > Basically why I asked the question - if the above should also be > wrapped, I am all for it. But if not, why some syscalls are special? I hope I've answered this to some extent. If not please elaborate on what specific things aren't clear. Rich
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