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    SubjectRe: [PATCH 3/3] exec: Allow do_coredump to wait for user space pipe readers to complete (v5)
    Neil, the changelog is not right,

    On 07/01, Neil Horman wrote:
    >
    > We basically add ourselves as an additional
    > reader (to prevent cleanup of the pipe), write the dump in ->core_dump(),

    This is not what we do. We do not and must not inc readers before
    ->core_dump(). We only do this in wait_for_dump_helpers().

    > note that we add ourselves as a reader before writing the
    > file. this closes the race in the window between the time we write the dump and
    > the time we start checking for the user space process to be done with the pipe.

    again, this doesn't match the patch.

    > +static void wait_for_dump_helpers(struct file *file)
    > +{
    > + struct pipe_inode_info *pipe;
    > +
    > + pipe = file->f_path.dentry->d_inode->i_pipe;
    > +
    > + pipe_lock(pipe);
    > + pipe->readers++;
    > + pipe->writers--;
    > + while (pipe->readers > 1) {
    > + wake_up_interruptible_sync(&pipe->wait);
    > + kill_fasync(&pipe->fasync_readers, SIGIO, POLL_IN);
    > + pipe_wait(pipe);
    > + }
    > +
    > + /*
    > + * This reclaims the additional readers count we took in
    > + * do_coredump
    > + */

    now the comment is wrong.

    Can't understand why do you change readers/writers unconditianally,
    we shouldn't have the false wakeups since ->writers == 0, but OK.

    Oleg.



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