On Wed 04-02-15 01:48:23, Pasi Sjöholm wrote: > On 03.02.2015 15:14, Michal Hocko wrote: > >> It is possible to get kernel in deadlock-state if swap_lock is not locked > >> with spin_lock_bh by calling si_swapinfo() simultaneously through > >> timer_function and registered vm shinker callback-function. > >> > >> BUG: spinlock recursion on CPU#0, main/2447 > >> lock: swap_lock+0x0/0x10, .magic: dead4ead, .owner: main/2447, .owner_cpu: 0 > >> [<c010b938>] (unwind_backtrace+0x0/0x11c) from [<c03e9be0>] (do_raw_spin_lock+0x48/0x154) > >> [<c03e9be0>] (do_raw_spin_lock+0x48/0x154) from [<c0226e10>] (si_swapinfo+0x10/0x90) > >> [<c0226e10>] (si_swapinfo+0x10/0x90) from [<c04d7e18>] (timer_function+0x24/0x258) > > Who is calling si_swapinfo from timer_function? AFAICS the vanilla > > kernel doesn't do that. Or am I missing something? > > Nothing in vanilla kernel, but "memnotify" > (https://lkml.org/lkml/2012/1/17/182) together with modified > lowmemorykiller (drivers/staging/android/lowmemorykiller.c) which takes > in account also the available swap (calling si_swapinfo as well) will > cause the deadlock. > > Memnotify uses timer (with backoff) for checking the memory pressure > which can be then used to let the processes itself adjust their memory > pressure before getting killed by the modified lowmemorykiller. We are not usually changing the core kernel for an out of tree functionality. So NAK to this patch. -- Michal Hocko SUSE Labs -- To unsubscribe, send a message with 'unsubscribe linux-mm' in the body to majordomo@xxxxxxxxx. For more info on Linux MM, see: http://www.linux-mm.org/ . Don't email: <a href=mailto:"dont@xxxxxxxxx";> email@xxxxxxxxx </a>