Messages in this thread | | | Date | Mon, 2 Apr 2007 14:34:49 +0200 | From | Ingo Molnar <> | Subject | Re: [PATCH] i386: fix file_read_actor() and pipe_read() for original i386 systems |
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* Thomas Gleixner <tglx@linutronix.de> wrote:
> The __copy_to_user_inatomic() calls in file_read_actor() and > pipe_read() are broken on original i386 machines, where WP-works-ok == > false, as __copy_to_user_inatomic() on such systems calls functions > which might sleep and/or contain cond_resched() calls inside of a > kmap_atomic() region. > > The original check for WP-works-ok was in access_ok(), but got moved > during the 2.5 series to fix a race vs. swap. > > Return the number of bytes to copy in the case where we are in an > atomic region, so the non atomic code pathes in file_read_actor() and > pipe_read() are taken.
neat trick! (v2.6.21 must-have me thinks.)
> This could be optimized to avoid the kmap_atomicby moving the check ^---- add space > for WP-works-ok into fault_in_pages_writeable(), but this is more > intrusive and can be done later. > > Signed-off-by: Thomas Gleixner <tglx@linutronix.de>
Acked-by: Ingo Molnar <mingo@elte.hu>
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