I. On Sat, 2018-07-07 at 10:23 +0200, Mike Galbraith wrote: > On Fri, 2018-07-06 at 17:56 -0400, Rik van Riel wrote: > > The mm_struct always contains a cpumask bitmap, regardless of > > CONFIG_CPUMASK_OFFSTACK. That means the first step can be to > > simplify things, and simply have one bitmask at the end of the > > mm_struct for the mm_cpumask. > > Otherwise virgin master.today grumbles. > > CC kernel/bounds.s > UPD include/generated/timeconst.h > UPD include/generated/bounds.h > CC arch/x86/kernel/asm-offsets.s > UPD include/generated/asm-offsets.h > CALL scripts/checksyscalls.sh > CHK include/generated/compile.h > HOSTCC usr/gen_init_cpio > UPD include/generated/compile.h > CC init/main.o > In file included from ./include/linux/cpumask.h:12:0, > from ./arch/x86/include/asm/cpumask.h:5, > from ./arch/x86/include/asm/msr.h:11, > from ./arch/x86/include/asm/processor.h:21, > from ./arch/x86/include/asm/cpufeature.h:5, > from ./arch/x86/include/asm/thread_info.h:53, > from ./include/linux/thread_info.h:38, > from ./arch/x86/include/asm/preempt.h:7, > from ./include/linux/preempt.h:81, > from ./include/linux/spinlock.h:51, > from ./include/linux/seqlock.h:36, > from ./include/linux/time.h:6, > from ./include/linux/stat.h:19, > from ./include/linux/module.h:10, > from init/main.c:16: > In function ‘bitmap_zero’, > inlined from ‘cpumask_clear’ at ./include/linux/cpumask.h:378:2, > inlined from ‘mm_init_cpumask’ at > ./include/linux/mm_types.h:504:2, > inlined from ‘start_kernel’ at init/main.c:560:2: > ./include/linux/bitmap.h:208:3: warning: ‘memset’ writing 64 bytes > into a region of size 0 overflows the destination [-Wstringop- > overflow=] > memset(dst, 0, len); > ^~~~~~~~~~~~~~~~~~~
I don't understand this one.
Inside init_mm we have this line:
.cpu_bitmap = { [BITS_TO_LONGS(NR_CPUS)] = 0},
which is the way the documentation suggests statically
allocated variable size arrays should be allocated
and initialized.
How does that result in a memset of the same size,
on the same array, to throw an error like above?
What am I doing wrong?
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