On Monday 18 January 2010, KOSAKI Motohiro wrote: > > Hi, > > > > I thing the snippet below is a good summary of what this is about. > > > > On Saturday 16 January 2010, Rafael J. Wysocki wrote: > > > On Saturday 16 January 2010, Maxim Levitsky wrote: > > > > On Sat, 2010-01-16 at 01:57 +0100, Rafael J. Wysocki wrote: > > > > > On Saturday 16 January 2010, Maxim Levitsky wrote: > > > > > > On Fri, 2010-01-15 at 23:03 +0100, Rafael J. Wysocki wrote: > > > > > > > On Friday 15 January 2010, Maxim Levitsky wrote: > > > > > > > > Hi, > > > > > > > > > > > > > > Hi, > > > > > > > > > > > > > > > I know that this is very controversial, because here I want to describe > > > > > > > > a problem in a proprietary driver that happens now in 2.6.33-rc3 > > > > > > > > I am taking about nvidia driver. > > > > > > > > > > > > > > > > Some time ago I did very long hibernate test and found no errors after > > > > > > > > more that 200 cycles. > > > > > > > > > > > > > > > > Now I update to 2.6.33 and notice that system will hand when nvidia > > > > > > > > driver allocates memory is their .suspend functions. > > > > > > > > > > > > > > They shouldn't do that, there's no guarantee that's going to work at all. > > > > > > > > > > > > > > > This could fail in 2.6.32 if I would run many memory hungry > > > > > > > > applications, but now this happens with most of memory free. > > > > > > > > > > > > > > This sounds a little strange. What's the requested size of the image? > > > > > > Don't know, but system has to be very tight on memory. > > > > > > > > > > Can you send full dmesg, please? > > > > > > > > I deleted it, but for this case I think that hang was somewhere else. > > > > This task was hand on doing forking, which probably happened even before > > > > the freezer. > > > > > > > > Anyway, the problem is clear. Now __get_free_pages blocks more often, > > > > and can block in .suspend even if there is plenty of memory free. > > > > This is suspicious, but I leave it to the MM people for consideration. > > > > > > I now patched nvidia to use GFP_ATOMIC _always_, and problem disappear. > > > > It isn't such great solution when memory is tight though.... > > > > > > > > This is going to hit hard all nvidia users... > > > > > > Well, generally speaking, no driver should ever allocate memory using > > > GFP_KERNEL in its .suspend() routine, because that's not going to work, as you > > > can readily see. So this is a NVidia bug, hands down. > > > > > > Now having said that, we've been considering a change that will turn all > > > GFP_KERNEL allocations into GFP_NOIO during suspend/resume, so perhaps I'll > > > prepare a patch to do that and let's see what people think. > > > > If I didn't confuse anything (which is likely, because it's a bit late here > > now), the patch below should do the trick. I have only checked that it doesn't > > break compilation, so please take it with a grain of salt. > > > > Comments welcome. > > Hmm.. > I don't think this is good idea. > > GFP_NOIO mean "Please don't reclaim if the page is dirty". It mean the system > have lots dirty pages, this patch might makes hung up. The point is to prevent the mm subsystem from using I/O. If there's a better way, please tell me. :-) > If suspend need lots memory, we need to make free memory before starting IO > suspending, I think. Suspend as such doesn't need a lot of memory, except for some drivers doing things they shouldn't do. However, there are a few problems that need to be addressed in general. First, we can't really guarantee that there's a lot of free memory available during suspend and some memory allocations are done indirectly, using GFP_KERNEL (for example, when new kernel threads are started). If one of these is done during suspend and it happens to cause the mm subsystem to start I/O on a suspended devices, the kernel will lock up. Second, there may be a memory allocation in progress when suspend is started that causes I/O to happen and races with the suspend process. If the latter wins the race, the I/O may be attempted on a suspended device and the kernel will lock up. My patch attempts to avoid these two problems as well as the problem with drivers using GFP_KERNEL allocations during suspend which I admit might be solved by reworking the drivers. Thanks, Rafael _______________________________________________ linux-pm mailing list linux-pm@xxxxxxxxxxxxxxxxxxxxxxxxxx https://lists.linux-foundation.org/mailman/listinfo/linux-pm
