On 2/23/10, Rafael J. Wysocki wrote: > On Tuesday 23 February 2010, Alan Jenkins wrote: >> On 2/22/10, Rafael J. Wysocki wrote: >> > On Monday 22 February 2010, Alan Jenkins wrote: >> >> Rafael J. Wysocki wrote: >> >> > On Friday 19 February 2010, Alan Jenkins wrote: >> >> > >> >> >> On 2/18/10, Rafael J. Wysocki wrote: >> >> >> >> >> >>> On Thursday 18 February 2010, Alan Jenkins wrote: >> >> >>> >> >> >>>> On 2/17/10, Rafael J. Wysocki wrote: >> >> >>>> >> >> >>>>> On Wednesday 17 February 2010, Alan Jenkins wrote: >> >> >>>>> >> >> >>>>>> On 2/16/10, Rafael J. Wysocki wrote: >> >> >>>>>> >> >> >>>>>>> On Tuesday 16 February 2010, Alan Jenkins wrote: >> >> >>>>>>> >> >> >>>>>>>> On 2/16/10, Alan Jenkins >> >> >>>>>>>> wrote: >> >> >>>>>>>> >> >> >>>>>>>>> On 2/15/10, Rafael J. Wysocki wrote: >> >> >>>>>>>>> >> >> >>>>>>>>>> On Tuesday 09 February 2010, Alan Jenkins wrote: >> >> >>>>>>>>>> >> >> >>>>>>>>>>> Perhaps I spoke too soon. I see the same hang if I run too >> >> >>>>>>>>>>> many >> >> >>>>>>>>>>> applications. The first hibernation fails with "not enough >> >> >>>>>>>>>>> swap" >> >> >>>>>>>>>>> as >> >> >>>>>>>>>>> expected, but the second or third attempt hangs (with the >> >> >>>>>>>>>>> same >> >> >>>>>>>>>>> backtrace >> >> >>>>>>>>>>> as before). >> >> >>>>>>>>>>> >> >> >>>>>>>>>>> The patch definitely helps though. Without the patch, I >> >> >>>>>>>>>>> see a >> >> >>>>>>>>>>> hang >> >> >>>>>>>>>>> the >> >> >>>>>>>>>>> first time I try to hibernate with too many applications >> >> >>>>>>>>>>> running. >> >> >>>>>>>>>>> >> >> >>>>>>>>>> Well, I have an idea. >> >> >>>>>>>>>> >> >> >>>>>>>>>> Can you try to apply the appended patch in addition and see >> >> >>>>>>>>>> if >> >> >>>>>>>>>> that >> >> >>>>>>>>>> helps? >> >> >>>>>>>>>> >> >> >>>>>>>>>> Rafael >> >> >>>>>>>>>> >> >> >>>>>>>>> It doesn't seem to help. >> >> >>>>>>>>> >> >> >>>>>>>> To be clear: It doesn't stop the hang when I hibernate with >> >> >>>>>>>> too >> >> >>>>>>>> many >> >> >>>>>>>> applications. >> >> >>>>>>>> >> >> >>>>>>>> It does stop the same hang in a different case though. >> >> >>>>>>>> >> >> >>>>>>>> 1. boot with init=/bin/bash >> >> >>>>>>>> 2. run s2disk >> >> >>>>>>>> 3. cancel the s2disk >> >> >>>>>>>> 4. repeat steps 2&3 >> >> >>>>>>>> >> >> >>>>>>>> With the patch, I can run 10s of iterations, with no hang. >> >> >>>>>>>> Without the patch, it soon hangs, (in disable_nonboot_cpus(), >> >> >>>>>>>> as >> >> >>>>>>>> always). >> >> >>>>>>>> >> >> >>>>>>>> That's what happens on 2.6.33-rc7. On 2.6.30, there is no >> >> >>>>>>>> problem. >> >> >>>>>>>> On 2.6.31 and 2.6.32 I don't get a hang, but dmesg shows an >> >> >>>>>>>> allocation >> >> >>>>>>>> failure after a couple of iterations ("kthreadd: page >> >> >>>>>>>> allocation >> >> >>>>>>>> failure. order:1, mode:0xd0"). It looks like it might be the >> >> >>>>>>>> same >> >> >>>>>>>> stop_machine thread allocation failure that causes the hang. >> >> >>>>>>>> >> >> >>>>>>> Have you tested it alone or on top of the previous one? If >> >> >>>>>>> you've >> >> >>>>>>> tested it >> >> >>>>>>> alone, please apply the appended one in addition to it and >> >> >>>>>>> retest. >> >> >>>>>>> >> >> >>>>>>> Rafael >> >> >>>>>>> >> >> >>>>>> I did test with both patches applied together - >> >> >>>>>> >> >> >>>>>> 1. [Update] MM / PM: Force GFP_NOIO during suspend/hibernation >> >> >>>>>> and >> >> >>>>>> resume >> >> >>>>>> 2. "reducing the number of pages that we're going to keep >> >> >>>>>> preallocated >> >> >>>>>> by >> >> >>>>>> 20%" >> >> >>>>>> >> >> >>>>> In that case you can try to reduce the number of preallocated >> >> >>>>> pages >> >> >>>>> even >> >> >>>>> more, >> >> >>>>> ie. change "/ 5" to "/ 2" (for example) in the second patch. >> >> >>>>> >> >> >>>> It still hangs if I try to hibernate a couple of times with too >> >> >>>> many >> >> >>>> applications. >> >> >>>> >> >> >>> Hmm. I guess I asked that before, but is this a 32-bit or 64-bit >> >> >>> system and >> >> >>> how much RAM is there in the box? >> >> >>> >> >> >>> Rafael >> >> >>> >> >> >> EeePC 701. 32 bit. 512Mb RAM. 350Mb swap file, on a "first-gen" >> >> >> SSD. >> >> >> >> >> > >> >> > Hmm. I'd try to make free_unnecessary_pages() free all of the >> >> > preallocated >> >> > pages and see what happens. >> >> > >> >> >> >> It still hangs in hibernation_snapshot() / disable_nonboot_cpus(). >> >> After apparently freeing over 400Mb / 100,000 pages of preallocated >> >> ram. >> >> >> >> >> >> >> >> There is a change which I missed before. When I applied your first >> >> patch ("Force GFP_NOIO during suspend" etc.), it did change the hung >> >> task backtraces a bit. I don't know if it tells us anything. >> >> >> >> Without the patch, there were two backtraces. The first backtrace >> >> suggested a problem allocating pages for a kernel thread (at >> >> copy_process() / try_to_free_pages()). The second showed that this >> >> problem was blocking s2disk (at hibernation_snapshot() / >> >> disable_nonboot_cpus() / stop_machine_create()). >> >> >> >> With the GFP_NOIO patch, I see only the s2disk backtrace. >> > >> > Can you please post this backtrace? >> >> Sure. It's rather like the one I posted before, except >> >> a) it only shows the one hung task (s2disk) >> b) this time I had lockdep enabled >> c) this time most of the lines don't have question marks. > > Well, it still looks like we're waiting for create_workqueue_thread() to > return, which probably is trying to allocate memory for the thread > structure. > > My guess is that the preallocated memory pages freed by > free_unnecessary_pages() go into a place from where they cannot be taken for > subsequent NOIO allocations. I have no idea why that happens though. > > To test that theory you can try to change GFP_IOFS to GFP_KERNEL in the > calls to clear_gfp_allowed_mask() in kernel/power/hibernate.c (and in > kernel/power/suspend.c for completness). Effectively forcing GFP_NOWAIT, so the allocation should fail instead of hanging? It seems to stop the hang, but I don't see any other difference - the hibernation process isn't stopped earlier, and I don't get any new kernel messages about allocation failures. I wonder if it's because GFP_NOWAIT triggers ALLOC_HARDER. I have other evidence which argues for your theory: [ successful s2disk, with forced NOIO (but not NOWAIT), and test code as attached ] Freezing remaining freezable tasks ... (elapsed 0.01 seconds) done. 1280 GFP_NOWAIT allocations of order 0 are possible 640 GFP_NOWAIT allocations of order 1 are possible 320 GFP_NOWAIT allocations of order 2 are possible [ note - 1280 pages is the maximum test allocation used here. The test code is only accurate when talking about smaller numbers of free pages ] 1280 GFP_KERNEL allocations of order 0 are possible 640 GFP_KERNEL allocations of order 1 are possible 320 GFP_KERNEL allocations of order 2 are possible PM: Preallocating image memory... 212 GFP_NOWAIT allocations of order 0 are possible 102 GFP_NOWAIT allocations of order 1 are possible 50 GFP_NOWAIT allocations of order 2 are possible Freeing all 90083 preallocated pages (and 0 highmem pages, out of 0) 190 GFP_NOWAIT allocations of order 0 are possible 102 GFP_NOWAIT allocations of order 1 are possible 50 GFP_NOWAIT allocations of order 2 are possible 1280 GFP_KERNEL allocations of order 0 are possible 640 GFP_KERNEL allocations of order 1 are possible 320 GFP_KERNEL allocations of order 2 are possible done (allocated 90083 pages) It looks like you're right and the freed pages are not accessible with GFP_NOWAIT for some reason. I also tried a number of test runs with too many applications, and saw this: Freeing all 104006 preallocated pages ... 65 GFP_NOWAIT allocations of order 0 ... 18 GFP_NOWAIT allocations of order 1 ... 9 GFP_NOWAIT allocations of order 2 ... 0 GFP_KERNEL allocations of order 0 are possible ... Disabling nonboot cpus ... ... PM: Hibernation image created Force enabled HPET at resume PM: early thaw of devices complete after ... msecs I'm not bothered by the new hang; the test code will inevitably have some side effects. I'm not sure why GFP_KERNEL allocations would fail in this scenario though... perhaps the difference is that we've swapped out the entire userspace so GFP_IO doesn't help. Regards Alan