Re: 2.6.33 pagemap endless read loop

[AmÃrico Wang]

On Sun, Jan 10, 2010 at 03:09:55AM +0100, Andi Kleen wrote:
>
>An LTP run on x86-64/2.6.33-rc3 run right now results in "proc01" hanging
>
>lr-x------  1 root root 64 2010-01-10 02:28 7 -> /proc/2679/task/2679/pagemap
>
>strace shows an endless loop of
>
>read(7, "\0\0\0\0\0\0\0\6\0\0\0\0\0\0\0\6\0\0\0\0\0\0\0\6\0\0\0"..., 1024) = 1024
>read(7, "\0\0\0\0\0\0\0\6\0\0\0\0\0\0\0\6\0\0\0\0\0\0\0\6\0\0\0"..., 1024) = 1024
>read(7, "\0\0\0\0\0\0\0\6\0\0\0\0\0\0\0\6\0\0\0\0\0\0\0\6\0\0\0"..., 1024) = 1024
>read(7, "\0\0\0\0\0\0\0\6\0\0\0\0\0\0\0\6\0\0\0\0\0\0\0\6\0\0\0"..., 1024) = 1024
>read(7, "\0\0\0\0\0\0\0\6\0\0\0\0\0\0\0\6\0\0\0\0\0\0\0\6\0\0\0"..., 1024) = 1024
>read(7, "\0\0\0\0\0\0\0\6\0\0\0\0\0\0\0\6\0\0\0\0\0\0\0\6\0\0\0"..., 1024) = 1024
>read(7, "\0\0\0\0\0\0\0\6\0\0\0\0\0\0\0\6\0\0\0\0\0\0\0\6\0\0\0"..., 1024) = 10
>
>cat of that file hangs in the same way so it seems like a kernel bug.
>A cat of /proc/2679/pagemap also hangs, in fact any pagemap cat seems to.
>

Are you sure?

On my 32bit machine, it runs for a long time, but finally exits.
>From the document of pagemap, it is the mapping of all the virtual pages
of a process, on x86-32, it should be 4G/4K = 1024*1024 pages, also
that when you 'cat' it, tty layer is involved to display it too.

-- 
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