Re: pipe/page fault oddness.

[Dave Jones]

On Tue, Sep 30, 2014 at 08:52:08AM -0700, Linus Torvalds wrote:

 > So if it's looping on that fault, what seems to happen is that the
 > page fault keeps happening.
 > 
 > Can you recreate this? Because if you can, please try to revert commit
 > e4a1cc56e4d7 ("x86: mm: drop TLB flush from ptep_set_access_flags").
 > Maybe the TLB has it read-only, and it doesn't get flushed, and the
 > page fault happens over and over again.

I left it spinning overnight in case someone wanted me to probe it
further, so I haven't tried reproducing it yet.  It took ~12 hours
yesterday before it got in that state.  I'll restart it, and tell it
to only use pipe fd's, which might speed things up a little.

If I can reproduce it, I'll then try that revert.

 > What kind of CPU is the problematic machine? There was some question
 > about just how architectural the whole "TLB entry causing a page fault
 > gets invalidated automatically" really is.

model name	: Intel(R) Core(TM) i5-4670T CPU @ 2.30GHz

	Dave

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