Date: Wed, 10 May 2006 12:01:57 +0800 From: David Xu <davidxu@freebsd.org> To: Daniel Eischen <deischen@freebsd.org> Cc: current@freebsd.org Subject: Re: Fine-grained locking for POSIX local sockets (UNIX domain sockets) Message-ID: <446165B5.7030006@freebsd.org> In-Reply-To: <Pine.GSO.4.64.0605092346340.21472@sea.ntplx.net> References: <20060506150622.C17611@fledge.watson.org> <20060509181302.GD3636@eucla.lemis.com> <20060509182330.GB92714@xor.obsecurity.org> <200605100726.28243.davidxu@freebsd.org> <44613469.2050000@freebsd.org> <4461522D.9060405@freebsd.org> <Pine.GSO.4.64.0605092346340.21472@sea.ntplx.net>
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Daniel Eischen wrote: > > On Wed, 10 May 2006, David Xu wrote: > >> One of the problems to implement it is that atomic operations, >> if there are multiple integer needs to be updated by kernel, >> userland maybe gets an inconsistent result, the way to avoid the >> problem is using two generation numbers. >> >> http://gsu.linux.org.tr/~mpekmezci/kernelapi/unitedlinux/arch/x86_64/kernel/vsyscall.c.html >> >> check do_vgettimeofday(struct timeval * tv): >> >> Another problem is how you tell userland the address of the kernel >> page ? do you use fixed address or tell it via program headers like >> the PT_TLS set by kernel, check /usr/src/lib/libc/gen/tls.c. > > > Can you not make a simple pseudo device driver and mmap the page? > mmap is fine if you don't care binary compatible, exporting a kernel page which can be executed by userland is more flexible, kernel can change it freely without having to change libc.help
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