On 10/30/2014 10:14 AM, Johannes Weiner wrote: >> The problem is that you are attempting to read 'locked' when you call >> > mem_cgroup_end_page_stat(), so it gets used even before you enter the >> > function - and using uninitialized variables is undefined. > We are not using that value anywhere if !memcg. What path are you > referring to? You're using that value as soon as you are passing it to a function, it doesn't matter what happens inside that function. >> > Yes, it's a compiler warning. > Could you provide that please, including arch, and gcc version? On x86, $ gcc --version gcc (GCC) 5.0.0 20141029 (experimental) [ 26.868116] ================================================================================ [ 26.870376] UBSan: Undefined behaviour in mm/rmap.c:1084:2 [ 26.871792] load of value 255 is not a valid value for type '_Bool' [ 26.873256] CPU: 4 PID: 8304 Comm: rngd Not tainted 3.18.0-rc2-next-20141029-sasha-00039-g77ed13d-dirty #1427 [ 26.875636] ffff8800cac17ff0 0000000000000000 0000000000000000 ffff880069ffbb28 [ 26.877611] ffffffffaf010c16 0000000000000037 ffffffffb1c0d050 ffff880069ffbb38 [ 26.879140] ffffffffa6e97899 ffff880069ffbbb8 ffffffffa6e97cc7 ffff880069ffbbb8 [ 26.880765] Call Trace: [ 26.881185] dump_stack (lib/dump_stack.c:52) [ 26.882755] ubsan_epilogue (lib/ubsan.c:159) [ 26.883555] __ubsan_handle_load_invalid_value (lib/ubsan.c:482) [ 26.884492] ? mem_cgroup_begin_page_stat (mm/memcontrol.c:1962) [ 26.885441] ? unmap_page_range (./arch/x86/include/asm/paravirt.h:694 mm/memory.c:1091 mm/memory.c:1258 mm/memory.c:1279 mm/memory.c:1303) [ 26.886242] page_remove_rmap (mm/rmap.c:1084 mm/rmap.c:1096) [ 26.886922] unmap_page_range (./arch/x86/include/asm/atomic.h:27 include/linux/mm.h:463 mm/memory.c:1146 mm/memory.c:1258 mm/memory.c:1279 mm/memory.c:1303) [ 26.887824] unmap_single_vma (mm/memory.c:1348) [ 26.888582] unmap_vmas (mm/memory.c:1377 (discriminator 3)) [ 26.889430] exit_mmap (mm/mmap.c:2837) [ 26.890060] mmput (kernel/fork.c:659) [ 26.890656] do_exit (./arch/x86/include/asm/thread_info.h:168 kernel/exit.c:462 kernel/exit.c:747) [ 26.891359] ? __this_cpu_preempt_check (lib/smp_processor_id.c:63) [ 26.892287] ? trace_hardirqs_on_caller (kernel/locking/lockdep.c:2559 kernel/locking/lockdep.c:2601) [ 26.893107] ? syscall_trace_enter_phase2 (arch/x86/kernel/ptrace.c:1598 (discriminator 2)) [ 26.893974] do_group_exit (include/linux/sched.h:775 kernel/exit.c:873) [ 26.894695] SyS_exit_group (kernel/exit.c:901) [ 26.895433] tracesys_phase2 (arch/x86/kernel/entry_64.S:529) [ 26.896134] ================================================================================ Thanks, Sasha -- 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>