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    SubjectRe: [RESEND] [PATCH] VFS: make file->f_pos access atomic on 32bit arch
    On Wed, 2008-10-08 at 10:32 +0200, Eric Dumazet wrote:

    > About dup() syscall, it wont help, since old and new descriptor points to
    > the same "struct file", definitly sharing file position, since first Unixes.
    > To quote the fine manual :
    > After successful return of dup or dup2, the old and new descriptors may
    > be used interchangeably. They share locks, file position pointers and
    > flags; for example, if the file position is modified by using lseek on
    > one of the descriptors, the position is also changed for the other.

    Ah, ok. I'll try to remember for next time I write a multi-threaded user
    app (which given the size of my kernel todo list won't be any time soon
    I guess ;-)

    > pread()/pwrite() are used my multi-threaded applications that want to share
    > a single "struct file".

    Yeah, pread/pwrite is good.

    > Or they must use some form of synchronization around
    > regular read()/write()/lseek() calls.
    > There is no generic f_pos race, only buggy applications.


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