lkml.org 
[lkml]   [2009]   [Jul]   [2]   [last100]   RSS Feed
Views: [wrap][no wrap]   [headers]  [forward] 
 
Messages in this thread
    Patch in this message
    /
    Date
    From
    SubjectRe: [PATCH 3/3] exec: Allow do_coredump to wait for user space pipe readers to complete (v6)
    (add Roland)

    Neil, I guess we both are tired of this thread, but I still have questions ;)

    On 07/01, Neil Horman wrote:
    >
    > +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);
    > + }
    > +
    > + pipe->readers--;
    > + pipe->writers++;
    > + pipe_unlock(pipe);
    > +
    > +}

    OK, I think this is simple enough and should work.

    This is not exactly correct wrt signals, if we get TIF_SIGPENDING this
    becomes a busy-wait loop.

    I'd suggest to do while (->readers && !signal_pending()), this is not
    exactly right too because we have other problems with signals, but
    this is another story.

    > void do_coredump(long signr, int exit_code, struct pt_regs *regs)
    > {
    > struct core_state core_state;
    > @@ -1862,6 +1886,8 @@ void do_coredump(long signr, int exit_code, struct pt_regs *regs)
    > current->signal->group_exit_code |= 0x80;
    >
    > close_fail:
    > + if (ispipe && core_pipe_limit)
    > + wait_for_dump_helpers(file);

    Oh. I thought I misread the first version, but now I see I got it right.
    And now I confused again.

    So, we only wait if core_pipe_limit != 0. Why?

    The previous version, v4, called wait_for_dump_helpers() unconditionally.
    And this looks more right to me. Once again, even without wait_for_dump()
    the coredumping process can't be reaped until core_pattern app reads all
    data from the pipe.

    I won't insist. However, anybody else please take a look?

    core_pipe_limit != 0 limits the number of coredump-via-pipe in flight, OK.

    But, should wait_for_dump_helpers() depend on core_limit_pipe != 0?
    Oleg.



    \
     
     \ /
      Last update: 2009-07-02 10:35    [W:0.055 / U:62.228 seconds]
    ©2003-2016 Jasper Spaans. hosted at Digital OceanAdvertise on this site