On Thu, 2007-07-12 at 19:21 -0700, Andrew Morton wrote:
> On Thu, 12 Jul 2007 19:00:12 -0700 Matt Helsley <[EMAIL PROTECTED]> wrote:
>
> > This patch avoids holding the mmap semaphore while walking VMAs in response
> > to
> > programs which read or follow the /proc/<pid|self>/exe symlink. This also
> > allows
> > us to merge mmu and nommu proc_exe_link() functions. The costs are holding
> > the
> > task lock, a separate reference to the executable file stored in the task
> > struct, and increased code in fork, exec, and exit paths.
> >
> > Signed-off-by: Matt Helsley <[EMAIL PROTECTED]>
> > ---
> >
> > Changelog:
> >
> > Hold task_lock() while using task->exe_file. With this change I haven't
> > been able to reproduce Chris Wright's Oops report:
> > http://lkml.org/lkml/2007/5/31/34
> > I used a 4-way, x86 system running kernbench. I also tried a 4-way
> > x86_64
> > system running pidof. I used oprofile during all runs but I could not
> > reproduce Chris' Oops with the new patch.
> >
> > Compiled and passed simple tests for regressions when patched against a
> > 2.6.20
> > and a 2.6.22 kernel. Regression tests included a variety of file operations
> > on
> > /proc/<pid|self>/exe such as stat, lstat, open, close, readlink, and
> > unlink. All
> > produced the expected, baseline output results.
> >
> > Andrew, please consider this patch for inclusion in -mm.
>
> I wish we had a description of the bug which this fixes. That email of
> Chris's is referencing code which diddles with task_struct.exe_file, but
> your patch _adds_ task_struct.exe_file, so I am all confused.
Chris was testing the patch. The patch isn't a bug fix so much as a
failed attempt to remove one use of the mm's mmap lock.
> Your patch does lots of fput()s under task_lock(), but fput() can sleep.
Ack, you're right.
> Plus what Al said.
Yup.
Thanks,
-Matt Helsley
-
To unsubscribe from this list: send the line "unsubscribe linux-kernel" in
the body of a message to [EMAIL PROTECTED]
More majordomo info at http://vger.kernel.org/majordomo-info.html
Please read the FAQ at http://www.tux.org/lkml/
