Messages in this thread | | | Date | Tue, 13 Dec 2011 23:43:16 +0100 (CET) | From | Thomas Gleixner <> | Subject | Re: [PATCH 2/3] DEBUGFS: Add per cpu counters |
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On Tue, 13 Dec 2011, Andi Kleen wrote: > \ > + __debugfs : AT(ADDR(__debugfs) - LOAD_OFFSET) { \ > + VMLINUX_SYMBOL(__start___debugfs) = .; \ > + *(__debugfs) \ > + VMLINUX_SYMBOL(__stop___debugfs) = .; \ > + } \ > + \
.... > +struct debugfs_counter { > + unsigned __percpu *ptr; > + const char *fn; > + const char *name; > +} __attribute__((aligned(sizeof(char *)))); > + > +/* Note: static doesn't work unlike DEFINE_PERCPU. Sorry. */ > +#define DEFINE_DEBUGFS_COUNTER(name_, file) \ > + DEFINE_PER_CPU(unsigned, name_ ## _counter); \ > + struct debugfs_counter name_ ## _pcpu_counter __used \ > + __attribute__((aligned(sizeof(char *)),section("__debugfs"),unused)) \ > + = { .ptr = &name_ ## _counter, .fn = file, .name = #name_ }; \
Sigh, we had that section forms an array problem more than once already. Why do you invent another variant and think that it will not explode?
Your alignment magic does not guarantee at all that the structs will form an array. The "aligned" attribute guarantees only the _MINIMUM_ alignment for a structure, but the compiler and the linker are free to align on larger multiples.
See commit 654986462 for details. That has been discussed to death and your solution wont work either across all the various compiler incarnations we have and will have.
Thanks,
tglx
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