On Wed, Sep 19, 2012 at 02:27:37PM -0700, David Rientjes wrote:
> On Wed, 19 Sep 2012, Linus Torvalds wrote:
>
> > > Create a 350 processes reading
> > > /sys/kernel/debug/kvm/spinlocks/histo_blocked
> > > file simultaneously in while loop for more than 3 hours on my box.
> >
> > You need to open the file a single time, and then after that sinelg
> > open (either threaded or with fork()) do multiple concurrent copies
> > something like
> >
> > for (;;) {
> > char buf[1024];
> > lseek(fd, 0, SEEK_SET);
>
> These are non-seekable files, so this will always fail. That makes the
> race much more difficult to trigger: the read needs to call
> u32_array_read() with both threads finding *ppos == 0 and then race
> between the kfree() and resetting of file->private_data pointer.
>
> [ I'm surprised that Dave was able to trigger this so often that he has
> 800MB of log. ]
Brainfart. 800Kb. Still, lots.
Dave
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