Messages in this thread | | | Date | Fri, 2 Mar 2012 14:44:54 -0500 | From | Don Zickus <> | Subject | Re: [PATCH 0/2 x86] fix some page faults in nmi if kmemcheck is enabled |
| |
On Tue, Feb 28, 2012 at 10:45:41AM +0800, Li Zhong wrote: > > > I'm not sure whether I understand it correctly. Do you mean that > > > nmiaction is initialized in register_nmi_handler(), which indicates it > > > will be used in nmi, so it shouldn't be marked non-present? > > > > No, you said that it marks memory non-present to detect uninitialized > > stuff, but since it is initialized, it shouldn't then be non-present, > > right? > > From my understanding of kmemcheck, the checking is based on the > non-present page. So while handling page fault, if the memory hasn't > been written before read, kmemcheck knows that it is uninitialized. > > I think it is used to find code errors, so it need mark all non-present, > to check if there are any access to uninitialized memory.
I am not sure if this is what your tool is catching, but someone pointed out to me privately that when panic'ing in an NMI, either the shutdown path I modified or the kdump path will register an NMI handler in an NMI context. Thus they will try to allocate memory in the NMI context.
So I will have to fix that. Wonder if that popular lockless memory allocator can help me there... otherwise I have to go back to pass in structs like the notifier blocks do.
Cheers, Don
| |