Messages in this thread | | | From | Andy Lutomirski <> | Date | Fri, 21 Nov 2014 08:38:07 -0800 | Subject | Re: frequent lockups in 3.18rc4 |
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On Nov 21, 2014 8:27 AM, "Tejun Heo" <tj@kernel.org> wrote: > > Hello, Andy. > > On Thu, Nov 20, 2014 at 03:55:09PM -0800, Andy Lutomirski wrote: > > That doesn't appear to have anything to with nmi though, right? > > I thought that was the main offender but, apparently, not any more. > > > Wouldn't this issue be fixed by moving the vmalloc_fault check into > > do_page_fault before exception_enter? > > Can you please elaborate why that'd fix the issue? I'm not > intimiately familiar with the fault handling so it'd be great if you > can give me some pointers in terms of where to look at.
do_page_fault is called directly from asm. It does:
prev_state = exception_enter(); __do_page_fault(regs, error_code, address); exception_exit(prev_state);
The vmalloc fixup is in __do_page_fault.
exception_enter does various accounting and tracing things, and I think that the recursion in stack trace I saw was in exception_enter.
If you move the vmalloc fixup before exception_enter() and return if the fault was from vmalloc, then you can't recurse. You need to be careful not to touch anything that uses RCU before exception_enter, though.
--Andy
> > Thanks. > > -- > tejun
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