Messages in this thread | | | Date | Wed, 25 Oct 2006 11:58:13 -0700 | From | Mike Kravetz <> | Subject | Re: oprofile can cause an NMI to schedule (was: [RT] scheduling and oprofile) |
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On Tue, Oct 24, 2006 at 08:54:42AM -0400, Steven Rostedt wrote: > On Tue, 24 Oct 2006, John Levon wrote: > > > On Mon, Oct 23, 2006 at 10:24:34PM -0400, Steven Rostedt wrote: > > in_atomic() is supposed to be true in this context, so the test in > > do_page_fault() catches it. > > Ahh, missed that one. So this is an issue that _only_ rt needs to fix. > OK, thanks for pointing that out.
Thanks! This issue is with an older RT kernel that I am running. In the version of the kernel I am running nmi_enter() and nmi_exit() are commented out as described here:
http://www.ussg.iu.edu/hypermail/linux/kernel/0508.1/1714.html
Newer RT kernels (such as linux-2.6.18-rt5) have reenabled the add_preempt_count/sub_preempt_count calls in nmi_enter/exit. If I understand correctly the reason one could not modify the preempt_count from NMI code is that it could have been in the process of being modified by non-NMI code. But, in recent RT kernels it appears that preempt_count is still a single word modified by both NMI and non-NMI code. What am I missing that now makes this safe?
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