Date: Mon, 5 Jun 2006 07:50:25 -0400 (EDT) From: Daniel Eischen <deischen@freebsd.org> To: MingyanGuo <guomingyan@gmail.com> Cc: delphij@gmail.com, freebsd-arch@freebsd.org Subject: Re: Why use `thread' as an argument of Syscalls? Message-ID: <Pine.GSO.4.64.0606050744190.13542@sea.ntplx.net> In-Reply-To: <1fa17f810606050044k2847e4a2i150eb934ed84006f@mail.gmail.com> References: <1fa17f810606050044k2847e4a2i150eb934ed84006f@mail.gmail.com>
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On Mon, 5 Jun 2006, MingyanGuo wrote: > Hi all, > I find that FreeBSD Syscalls always have an `thread' > argument, for example, preadv(/sys/kern/sys_generic.c) > has a `td' argument. But some Syscalls may rarely use > this argument, and thay ( and functions they invoke) can > get the `thread' who make the Syscall _easily_ via > `curthread' macro if needed. So the `thread' argument > seems not needed. > Can anybody tell me why use `thread' as an argument > of Syscalls? You could have asked "why use 'proc' as an argument of Syscalls" 12 years ago (or more). When the kernel became thread-aware (almost 5 years ago), most 'struct proc' arguments were changed to 'struct thread'. -- DE
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